168 results on '"Langosch D"'
Search Results
2. Structure and Expression of Inhibitory Glycine Receptors
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Betz, H., Langosch, D., Hoch, W., Prior, P., Pribilla, I., Kuhse, J., Schmieden, V., Malosio, M.-L., Matzenbach, B., Holzinger, F., Kuryatov, A., Schmitt, B., Maulet, Y., Becker, C.-M., Kito, Shozo, editor, Segawa, Tomio, editor, and Olsen, Richard W., editor
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- 1991
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3. Secondary structure and distribution of fusogenic LV-peptides in lipid membranes
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Ollesch, J., Poschner, B. C., Nikolaus, J., Hofmann, M. W., Herrmann, A., Gerwert, K., and Langosch, D.
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- 2008
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4. The role of transmembrane domains in membrane fusion
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Langosch, D., Hofmann, M., and Ungermann, C.
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- 2007
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5. Role of the Vam3p transmembrane segment in homodimerization and SNARE complex formation
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Roy, R., Peplowska, K., Rohde, J., Ungermann, C., and Langosch, D.
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Eukaryotes -- Research ,Cell membranes -- Chemical properties ,Cell membranes -- Structure ,Biological sciences ,Chemistry - Abstract
Homodimeric and heterooligomeric complexes containing Vam3p in vivo and in vitro are examined. The results reveal that a significant fraction of the yeast vascular SNARE Vam3p is a homodimer in detergent extracts of vacuolar membranes, which exists in parallel to the heterooligomeric SNARE complex, and homoderization, but not SNARE complex formation, depends on the transmembrane segment.
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- 2006
6. Understanding intramembrane proteolysis: from protein dynamics to reaction kinetics
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Langosch, D., primary, Scharnagl, C., additional, Steiner, H., additional, and Lemberg, M.K., additional
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- 2015
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7. Secondary structure and distribution of fusogenic LV-peptides in lipid membranes
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Ollesch, J., primary, Poschner, B. C., additional, Nikolaus, J., additional, Hofmann, M. W., additional, Herrmann, A., additional, Gerwert, K., additional, and Langosch, D., additional
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- 2007
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8. Mutations affecting transmembrane segment interactions impair adhesiveness of E-cadherin
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Huber, O., primary, Kemler, R., additional, and Langosch, D., additional
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- 1999
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9. Cyanotriphenylborate: subtype-specific blocker of glycine receptor chloride channels.
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Rundström, N, primary, Schmieden, V, additional, Betz, H, additional, Bormann, J, additional, and Langosch, D, additional
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- 1994
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10. Decreased agonist affinity and chloride conductance of mutant glycine receptors associated with human hereditary hyperekplexia.
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Langosch, D., primary, Laube, B., additional, Rundström, N., additional, Schmieden, V., additional, Bormann, J., additional, and Betz, H., additional
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- 1994
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11. Residues within transmembrane segment M2 determine chloride conductance of glycine receptor homo- and hetero-oligomers.
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Bormann, J., primary, Rundström, N., additional, Betz, H., additional, and Langosch, D., additional
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- 1994
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12. The atypical M2 segment of the beta subunit confers picrotoxinin resistance to inhibitory glycine receptor channels.
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Pribilla, I., primary, Takagi, T., additional, Langosch, D., additional, Bormann, J., additional, and Betz, H., additional
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- 1994
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13. Structure, diversity and synaptic localization of inhibitory glycine receptors
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Betz, H., primary, Kuhse, J., additional, Fischer, M., additional, Schmieden, V., additional, Laube, B., additional, Kuryatov, A., additional, Langosch, D., additional, Meyer, G., additional, Bormann, J., additional, Rundström, N., additional, Matzenbach, B., additional, Kirsch, J., additional, and Ramming, M., additional
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- 1994
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14. Structure and Biology of Inhibitory Glycine Receptors
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BETZ, H., primary, LANGOSCH, D., additional, RUNDSTRÖM, N., additional, BORMANN, J., additional, KURYATOV, A., additional, KUHSE, J., additional, SCHMIEDEN, V., additional, MATZENBACH, B., additional, and KIRSCH, J., additional
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- 1993
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15. Residues within transmembrane segment M2 determine chloride conductance of glycine receptor homo- and hetero-oligomers.
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Bormann, J., primary, Rundström, N., additional, Betz, H., additional, and Langosch, D., additional
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- 1993
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16. Homology and analogy in transmembrane channel design: Lessons from synaptic membrane proteins
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Betz, H., Becker, C. -M., Grenningloh, G., Hoch, W., Knaus, P., Langosch, D., Malosio, M. L., Schmitt, B., and Thomas, L.
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- 1989
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17. The atypical M2 segment of the beta subunit confers picrotoxinin resistance to inhibitory glycine receptor channels.
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Pribilla, I., primary, Takagi, T., additional, Langosch, D., additional, Bormann, J., additional, and Betz, H., additional
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- 1992
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18. Primary structure and alternative splice variants of gephyrin, a putative glycine receptor-tubulin linker protein
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Prior, P., primary, Schmitt, B., additional, Grenningloh, G., additional, Pribilla, I., additional, Multhaup, G., additional, Beyreuther, K., additional, Maulet, Y., additional, Werner, P., additional, Langosch, D., additional, Kirsch, J., additional, and Betz, H., additional
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- 1992
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19. The 93-kDa glycine receptor-associated protein binds to tubulin.
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Kirsch, J., primary, Langosch, D., additional, Prior, P., additional, Littauer, U.Z., additional, Schmitt, B., additional, and Betz, H., additional
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- 1991
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20. Heterogeneity of the Inhibitory Glycine Receptor
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KUHSE, J., primary, BECKER, C.-M., additional, SCHMIEDEN, V., additional, HOCH, W., additional, PRIBILLA, I., additional, LANGOSCH, D., additional, MALOSIO, M.-L., additional, MUNTZ, M., additional, and BETZ, H., additional
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- 1991
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21. Peptide mimics of the vesicular stomatitis virus G-protein transmembrane segment drive membrane fusion in vitro.
- Author
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Langosch, D, Brosig, B, and Pipkorn, R
- Abstract
The efficiency of cell-cell fusion mediated by heterologously expressed vesicular stomatitis virus G-protein has previously been shown to be affected by mutating its transmembrane segment. Here, we show that a synthetic peptide modeled after this transmembrane segment drives liposome-liposome fusion. Addition of millimolar Ca(2+) concentrations strongly potentiated the effect of the peptides suggesting that Ca(2+)-mediated liposome aggregation supports the activity of the peptide. Peptide-driven fusion was suppressed by lysolipid, an established inhibitor of natural membrane fusion, and involved inner and outer leaflets of the liposomal bilayer. Thus, transmembrane segment peptide-driven liposome fusion exhibits important hallmarks characteristic of natural membrane fusion. Importantly, the mutations previously shown to attenuate the function of full-length G-protein in cell-cell fusion also attenuated the fusogenicity of the peptide, albeit in a less pronounced fashion. Therefore, the function of the peptide mimic is dependent on its primary structure, similar to full-length G-protein. Together, our data suggest that the G-protein transmembrane segment is an autonomous functional domain. We propose that it acts at a late step in membrane fusion elicited by vesicular stomatitis virus.
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- 2001
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22. A heptad motif of leucine residues found in membrane proteins can drive self-assembly of artificial transmembrane segments.
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Gurezka, R, Laage, R, Brosig, B, and Langosch, D
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Specific interactions between alpha-helical transmembrane segments are important for folding and/or oligomerization of membrane proteins. Previously, we have shown that most transmembrane helix-helix interfaces of a set of crystallized membrane proteins are structurally equivalent to soluble leucine zipper interaction domains. To establish a simplified model of these membrane-spanning leucine zippers, we studied the homophilic interactions of artificial transmembrane segments using different experimental approaches. Importantly, an oligoleucine, but not an oligoalanine, se- quence efficiently self-assembled in membranes as well as in detergent solution. Self-assembly was maintained when a leucine zipper type of heptad motif consisting of leucine residues was grafted onto an alanine host sequence. Analysis of point mutants or of a random sequence confirmed that the heptad motif of leucines mediates self-recognition of our artificial transmembrane segments. Further, a data base search identified degenerate versions of this leucine motif within transmembrane segments of a variety of functionally different proteins. For several of these natural transmembrane segments, self-interaction was experimentally verified. These results support various lines of previously reported evidence where these transmembrane segments were implicated in the oligomeric assembly of the corresponding proteins.
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- 1999
23. Isolation and characterization of a second nitrogenase Fe-protein from Azotobacter vinelandii.
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Hales, B J, Langosch, D J, and Case, E E
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Wild-type Azotobacter vinelandii strain UW was transformed with plasmid pDB12 to produce a species (LS10) unable to synthesize the structural proteins of component 1 and component 2 of native nitrogenase. A spontaneous mutant of this strain was isolated (LS15) which can grow by nitrogen fixation in the presence or absence of either Mo or W. It is proposed that LS15 fixes nitrogen solely by an alternative nitrogen-fixing system which previously has been hypothesized to exist in A. vinelandii. Under nitrogen-fixing conditions, LS15 synthesizes a protein similar to component 2 (Av2) of native nitrogenase in that it can complement native component 1 (Av1) for enzymatic activity. Isolation and characterization of this second component 2 shows it to be a 4Fe-4S protein of molecular mass about 62 kDa and is antigenically similar to Av2. This protein is also similar to Av2 in that in the reduced state it possesses a rhombic ESR spectrum in the g = 2 region, which changes to an axial spectrum upon addition of MgATP. It is suggested that this second Fe-protein is associated with the alternative nitrogen-fixing system in A. vinelandii.
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- 1986
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24. Conserved quaternary structure of ligand-gated ion channels: the postsynaptic glycine receptor is a pentamer.
- Author
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Langosch, D, Thomas, L, and Betz, H
- Abstract
The postsynaptic glycine receptor of rat spinal cord is a glycosylated membrane protein that, after affinity purification, contains membrane-spanning subunits of Mr 48,000 and 58,000 and an associated peripheral polypeptide of Mr 93,000. Here, the quaternary structure of the transmembrane core of the receptor was investigated by chemically crosslinking its subunits. Upon treatment with crosslinking reagents of different side-chain specificities and lengths, a consistent set of adducts up to Mr 260,000 was detected after separation by NaDodSO4/PAGE. The observed pattern of adducts was similar irrespective of whether purified receptor protein or synaptosomal membranes were crosslinked. Compositional analysis revealed that the crosslinked adducts contained the Mr 48,000 and 58,000 subunits in varying ratios but not the peripheral Mr 93,000 polypeptide. Thus adducts of intermediate molecular weight represent dimers, trimers, and tetramers of the transmembrane subunits, whereas the major adduct of Mr 260,000 corresponds to a pentameric assembly of subunits forming the ion channel of the glycine receptor. This subunit arrangement is similar to that reported for the nicotinic acetylcholine receptor of fish electric organ and skeletal muscle. Hence, we suggest that the different ligand-gated ion channels of excitable membranes share a similar quaternary structure.
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- 1988
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25. A single residue in the transmembrane domain of the erythropoietin receptor regulates lipid raft localization and signal amplification
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Becker, V., Ketteler, R., Schilling, M., Baumann, U., Heinrich, Ac, Ruan, W., Sengupta, D., Langosch, D., Smith, Jc, and Ursula Klingmüller
26. Importance of Arg-219 for correct biogenesis of a1 homooligomeric glycine receptors
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Langosch, D., Herbold, A., Schmieden, V., and Borman, J.
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- 1993
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27. New Approaches in Context-based Protein Function Prediction
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Kolesov, Grigory, Langosch, D. (Univ.-Prof. Dr.rer.nat.habil.), Mewes, H.-W. (Univ.-Prof. Dr.rer.nat.), and Dandekar, T. (Univ.-Prof. Dr.med.)
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bioinformatics ,genomics ,functional prediction ,gene order ,Biowissenschaften, Biologie ,ddc:570 ,Bioinformatik ,Genomik ,Funktionsvorhersage - Abstract
In this work we analyze genomic neighborhood of a gene as a source of functional information. Using concept of Similarity-Neighborhood graph we show presence of non-trivial relations between genomic neighbors in the context of several genomes. We also show that while for prokaryotes the existence of such relations can be deduced from the operonic organization of prokaryotic genomes, these relations can also be detected in the eukaryotic genomes where such organization is not common (with notable exception of Caenorhabditis elegans and possibly othermembers of Nematodae). We demonstrate applicability of the our method for uncovering gene's function and studying properties of genomes. We also demonstrate the techniques and tools developed for the analysis of genomic data. PEDANT genome system has been developed by our group and served as a main foundation for development of Similarity-Neighborhood approach, with the latter coming into life as a separate gene-function prediction tool - SNAPper web server. We discuss the techniques hiding behind our all-against-all protein alignment database, which has been developed as part of PEDANT genome analysis system. Such database is the requirement for nearly any cross-genome comparison approach, as it provides the basis for delineating of orthologous and paralogous groups of genes. One of such approaches - phylogenetic profiling, has been implemented by us in collaboration with Philip Wong and Walid Houry of University of Toronto, as highly flexible Web-based tool called PWP. The Jaba visualisation tool which we developed for manual analysis of the genomes and multiple gene predictions and which has been extensively used in several genome projects, including large eukaryotic genome projects such as Arabidopsis thaliana and Neurospora crassa is also presented. Wir untersuchen genomische Nachbarschaft as eine Quelle funktioneller Informationen über Gene. Basierend auf dem Konzept von Simlarity-Neighborhood Graphen wird gezeigt, wie nicht-triviale Verhältnisse zwischen benachbarten Genen aufgedeckt werden können. Während in Prokaryoten das Vorhandensein solcher Korrelationen auf die Operonstrukturen zurückverfolgt werden kann, wurde dieses Phänomen auch in einigen eukaryontischen Genomen entdeckt, wo Operone in der Regel nicht vorkommen. Wir demonstrieren die Anwendbarkeit dieser Methode zur Genfunktionsvorhersage und Untersuchung von Genomeigenschaften. Darüber hinaus werden folgende Techniken zur Genomanalyse vorgestellt: a) Eine Web-Ressource zur Untersuchung von Similarity-Neighborhood Graphen, b) Die Datenbank von Alignments zur Berechnung von paralogen und orthologen Gengruppen, c) Ein phylogenetic profiling Werkzeug, d) Ein Programm zur Visualisierung genomischer Informationen und multiplen Genvorhersagen.
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- 2006
28. The human Apolipoprotein D as a scaffold for novel binding proteins with affinity for protein antigens
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Vogt, Martin, Skerra, A. (Univ.-Prof. Dr.), and Langosch, D. (Univ.-Prof. Dr.)
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Biowissenschaften, Biologie ,apolipoprotein D ,anticalin ,combinatorial biochemistry ,phage display ,protein design ,ddc:570 ,ddc:540 ,Chemie ,Apolipoprotein D ,Anticalin ,kombinatorische Biochemie ,Phage Display ,Protein Design - Abstract
Die Bindungseigenschaften des humanen Apolipoprotein D (ApoD), eines Vertreters der Lipocalin-Proteinfamilie, wurden so verändert, daß anstelle der natürlichen niedermolekularen Liganden ein vorgegebenes Protein-Antigen erkannt wird. Dazu wurde die gentechnische Produktion des ApoD in E. coli etabliert und dessen Bindungseigenschaften charakterisiert, wobei Progesteron und Arachidonsäure als physiologische Liganden bestätigt wurden, nicht jedoch andere Verbindungen, die zuvor als Liganden diskutiert worden waren. Durch kombinatorisches Protein-Design wurde eine Varianten-Bibliothek des ApoD hergestellt, aus der ein sogenanntes Anticalin mit Bindungsaktivität für den exemplarischen Liganden Hämoglobin mit einer Komplex-Dissoziationskonstante von 2,16 µM isoliert wurde. The binding properties of human apolipoprotein D (ApoD), a member of the lipocalin protein family, were modified in a way that the protein recognized a prescribed antigen instead of its natural low molecular weight ligands. Therefore, the production of ApoD in E. coli was established and its binding properties were analyzed. Progesterone and arachidonic acid formed complexes with ApoD, but not other compounds which were dicussed as ligands. By means of combinatorial design, a library of variants of ApoD was generated, from which a so called anticalin with binding activity for an exemplary ligand, hemoglobin, with a complex dissociation constant of 2.16 µM was isolated.
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- 2005
29. Functional analysis of heterologous holin proteins in a lDSthf genetic background
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Vukov, Natascha, Scherer, S. (Univ.-Prof. Dr.), and Langosch, D. (Univ.-Prof. Dr.)
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Lambda Phage ,Lyse ,Membranprotein ,Holine ,Biowissenschaften, Biologie ,ddc:570 ,phage lambda ,lysis ,membrane protein ,holin - Abstract
Holins are small hydrophobic proteins causing non-specific membrane lesions at the end of bacteriophage multiplication, to promote access of the murein hydrolase to their substrate. We have established a lambda-delta-Sthf genetic system, which enables functional expression of holins from various phages in an isogenic phage lambda background, and allows qualitative evaluation of their ability to support lysis of Escherichia coli cells. Synthesis of holins is under control of native lambda transcription and translation initiation signals, and the temperature-sensitive CIts857 repressor. A number of different holins were tested in this study. The opposing action of phage lambda S105 and S107 holin variants in lysis timing could be confirmed, whereas we found evidence for a functionally non-homologous dual translational start motif in the Listeria phage Hol500 holin. The largest holin known, HolTW from a Staphylococcus aureus phage, revealed an early lysis phenotype in the lDSthf background, which conferred a plaque forming defect due to premature lysis. Mutant analysis revealed that an altered C-terminus and/or a V52L substitution were sufficient to delay lysis and enable plaque formation. These results suggest that the extensively charged HolTW C-teminus may be important in regulation of lysis timing. Gene 17.5 product of E. coli phage T7, and Gp T from T4 was found to support sudden, saltatory cell lysis in the lDSthf background, which clearly confirms their holin character. In conclusion, lDSthf offers a useful genetic tool for studying the structure-function relationship of the extremely heterogeneous group of holin protein orthologs. MscL, the mechanosensitive channel forming protein, which shares main structural features with holins of was unable to complement the lysis defect of lDSthf, confirming specitivity of holin function. The functional properties of Hol118 holin from Listeria monocytogenes bacteriophage A118 were analysed in detail. The gene was cloned into lDSthf, whose CIts857 repressor allows precise estimation of the cell lysis event mediated by a cloned holin, through the possibility to heat-induce the lytic cycle in lysogenized E. coli. Native hol118 caused relatively late cell lysis, beginning at 90 min after induction. Lysis could not be prematurely triggered with energy poisons, indicating that the energized membrane does not inhibit permeabilization by this holin. Immunological analyses demonstrated that Hol118 appears in the inner membrane fraction of infected cells 20 min after phage multiplication starts in induced E. coli. Hol118 could also be detected in A118-infected Listeria monocytogenes cells. Since hol118 features a dual start, different N-terminally modified Hol118 variants were tested for differences in lytic properties. Changing the ATGs encoding M1 or M4 into CTG had no significant influence on lysis timing, indicating that these alleles do not assume the effector/inhibitor roles described for S. Toeprinting assays of hol118 mRNA revealed use of an additional ATG start codon at position 40, encoding M14. Using in vitro approaches, we were able to demonstrate that a Hol118(83) variant is actually translated from the hol118 transcripts. This N-terminally truncated holin lacks the first predicted transmembrane domain. Although it appears in the cytoplasma membrane, it is functionally deficient and unable to complement R in lDSthf. Changing the M14-encoding ATG into codons not used as translational starts (M14I, M14L) resulted in an accelerated, premature lysis phenomenon, pointing to an inhibitor function of Hol118(83). This hypothesis was further supported by the observation that hol118(83) expressed in trans also inhibited holin function. This suggests that the first transmembrane domain is indispensable for the permeablization process leading to pore formation. Based on our findings, we propose a new model of holin functional regulation, where the intragenic Hol118(83) acts as an functional inhibitor, and therefore constitutes a key part of the lysis clock of A118. The strict regulation and inhibition of poreforming aids to explain the long latend period of Listeria phage A118, where the onset of lysis under optimal conditions takes approximately 70 min, more than twice the time needed by phage l. The functional properties of Hol500 holin from Listeria monocytogenes bacteriophage A500 was also analysed, and compared to Hol118 and to Hol2438 from Listeria innocua. Native hol500 caused cell lysis, beginning at 60 min after induction of lDSthf::hol500. Here, lysis could be prematurely triggered with energy poisons, indicating that the energized membrane inhibits permeabilization by this holin. N-terminally modified Hol500 variants were tested for differences in lytic properties. Changing M14-encoding ATG into ATT resulted in accelerated cell lysis. Toeprinting assays on hol500 mRNA revealed use of M14 as a translational start pointing to the synthesis of a truncated protein from this position. We have shown that Hol118(83), the intragenic inhibitor of Hol118, can also inhibit Hol500 lysis, which further supports our model for regulation of lysis timing in these very similar Listeria holins. Hol2438 differs from Hol500 in the reduced net charge of the C-terminal domain, due to the lack of one lysine residue at the C-terminal end. This difference had a significant influence on lysis timing, confirming the crucial role for the distal part of the C-terminus of Listeria holins tested in this work. In dieser Arbeit wurde die Struktur-Funktionsbeziehung von Holinen, phagencodierten Membranproteinen in einem einheitlichem genetischen Hintergrund untersucht. Für den zeitlichen Verlauf und die effektive intrazelluläre Lyse von phageninfizierten Bakterien ist außer den Endolysinen als Mureinhydrolasen meist noch ein zusätzliches Protein nötig, welches über Porenbildung in der Cytoplasma-Membran den Durchtritt der Endolysine an das Zellwand-Substrat ermöglicht. Diese kleinen hydrophoben Proteine werden aufgrund ihrer Funktion als Holine bezeichnet. Die Primär-Sequenzen der Holinen sind sehr heterogen; es gibt fast keine signifikanten Homologien, außer bei einzelnen Phagen von taxonomisch sehr nah verwandten Bakterien. Hier wurde ein Derivat von dem Phagen Lambda-gt11 konstruiert, Lambda-delta-Sthf, in dem das S Holin Gen vollständig deletiert wurde und eine eingeführte EcoRI - Schittstelle die Einklonierung einen heterologen Holin Gens erlaubte. Die Lysisgen-Kassette mit dem klonierten Holin Gen konnte mittels Prophagen-Induktion von lDSthf durch Inaktivierung des temperatur-sensitiven Cits857 Repressors exprimiert werden. Beobachtung und Verlauf des zeitlichen Verlaufes der Lyse ermöglichte einen Vergleich der Funktion verschiedener Holine. Als erstes wurden die in der Funktion unterschiedliche Varianten von Lambda S getestet. Die Expression des S105 Effektors führte zu sehr schneller, vorzeitiger Lyse, während der Inhibitor S107 deutlich schlechter lysierte. Das größte bis jetzt bekannte Holin des Staphylococcus aureus Phagen Twort verursachte eine vorzeitige Lyse die zu einem "Plaque Defekt" führte. Die Holine der virulenten E. coli Phagen T4 (gp T) und T7 (gp 17,5) führten zu einer schnellen, abrupten Lyse, die für diese in ihrer Struktur sehr unterschiedlichen Holinen fast identisch war. Außerdem wurde gezeigt das ein porenbildendes Membranprotein, MscL, welches den Holinen gemeinsame Sekundär-Strukturmerkmalen aufweist, in lDSthf keine Lyse verursachte. Das bedeutet, das die Funktion auch bei der extermen Heterogenität der primären Holinstrukturen spezifisch ist. Die membranpermeabilisierende Aktivität des Hol118 Holin des Listeria monocytogenes Bakteriophagen A118 wurde in lDSthf getestet. lDSthf::hol118 lysierte E. coli Zellen relativ spät, 90 min nach Induktion. Die Lyse konnte auch nicht durch eine Zerstörung des Membranpotentials vorzeitig induziert werden. Zwanzig Minuten nach der lDSthf::hol118 Prophagen-Induktion war Hol118 in der inneren Membranfraktion von E. coli immunologisch nachweisbar. Außerdem wurde das Hol118 Protein in der Membran der Listeria Zellen nach A118 Infektion nachgewiesen. Um den potentiellen doppelten Start zu untersuchen, wurden Mutationen im N-Terminus eingeführt und der Effekt dieser Mutationen getestet. Veränderungen des ersten und vierten ATGs hatten keinen bedeutenden Einfluß auf den zeitlichen Verlauf der Lyse. "Toeprinting" auf der hol118 mRNS zeigte ein zusätzliches ATG Start Kodon an Nukleotid-Position 40 in hol118. In vitro Versuche zeigten daß diese Hol118(83) Variante von hol118 tatsächlich translatiert wird. Das gekürzte Protein kann nur zwei Transmembrandomänen in der Membran bilden, ist nicht mehr funktionsfähig und kann R in lDSthf nicht mehr komplementieren. Diese funktionellen Eigenschaften von Hol118(83) zeigten eindeutig das die erste Transmembrandomäne für die porenbildende Funktion des Holin essentiell ist. Ersatz des M14 ATG Kodons in die für die Initiation der Translation in der Regel nicht verwendeten CTG or ATT (M14L, M14I) führte zu zunehmend schnelleren Lyse. Diese Ergebnisse deuten auf eine Inhibitor-Funktion für Hol118(83) hin. Hol118(83) inhibierte auch in trans Hol118 induzierte Lyse. Auf Grund dieser Ergebnisse wird ein neues Modell postuliert: Hol118(83), das an Nukleotid-Position 40 des hol118 Gens startet funktioniert als der Inhibitor der Lyse, und hat somit einen Einfluß auf die Regulation der Dauer der Latenzphase des A118 Bakteriophagen. Die Aminosäuresequenzen der Holine Hol118 und Hol500 unterscheiden sich nur in sieben Aminosäuren, haben aber unterschiedliche membranpermeabilisierende Aktivitäten in lDSthf. lDSthf::hol500 lysierte die E. coli Zellen schneller und effizienter als Hol118. Das Membranpotential der Zelle hatte hier einen inhibitorischen Effekt auf die Lyse; die Inaktivierung des Membranpotentials führte zu einer vorzeitigen Lyse. Wie bei Hol118 wurden Mutationen in den N-Terminus eingeführt und getestet. Die Änderungen des vierten Methionins in Leucin oder Isoleucin verstärkten die lytische Aktivität, während die Inaktivierung des ersten ATGs zu einer verzögerten Lyse führte. "Toeprinting" auf der hol500 mRNS zeigte ebenfalls ein zusätzliches intragenes ATG Start Kodon an Position 40. Die Änderung ATG zu ATT hatte einen identischen funktionellen Effekt wie in hol118: Beschleunigung der Lyse. Exprimiert in trans inhibierte Hol118(83) die Hol500-induzierte Lyse. Da die Unterschiede in der Aminosäuresequenzen zwischen Hol118 und Hol500 minimal sind kann das postulierte Modell der Lyseinhibition für A118 auf den Phagen A500 erweitert werden. Hol2438 unterscheidet sich von Hol500 nur in einer Aminosäure des C-terminalen Bereichs. Das fehlende Lysin reduzierte die positive Ladung des C-Terminus was im Vergleich zu Hol500 zu einer Beschleunigung der Lyse führte.
- Published
- 2005
30. Konstruktion eines bispezifischen F(ab)2-Fragments zur Immuntherapie des Hodgkin-Lymphoms
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Schlapschy, Martin, Skerra, A. (Univ.-Prof. Dr.), and Langosch, D. (Univ.-Prof. Dr.)
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CD16 ,CD30 ,Hodgkin-Lymphom ,Fab-Fragment ,F(ab)2 -Fragment ,bispezifische Antikörper ,Humanisierung ,Affinitäts-Maturierung ,bakterielle Proteinproduktion ,Zufalls-Mutagenese ,Antikörper Engineering ,DTNB ,Biowissenschaften, Biologie ,ddc:570 ,ddc:540 ,Medizin ,Chemie ,ddc:610 ,Hodgkin-Lymphoma ,Fab fragment ,F(ab)2 fragment ,bispecific antibodies ,humanization ,affinity maturation ,bacterial protein production ,random mutagenesis ,antibody engineering - Abstract
In den letzten Jahren wurden zur Immuntherapie von Tumorerkrankungen vermehrt bispezifische F(ab)2-Fragmente entwickelt. Insbesondere wird die Strategie verfolgt, cytotoxische Effektorzellen durch spezifische Vermittlung eines Kontakts zwischen den Tumorzellen und dem tumorassoziierten Antigen lokal zu aktivieren. Beispielsweise wird die Therapie des Hodgkin-Lymphoms angestrebt, indem das Fab-Fragment HRS3 einerseits das Antigen CD30 auf den lymphatischen Tumorzellen erkennt und andererseits das Antikörperfragment A9 den Fc-gamma-Rezeptor III (CD16) auf natürlichen Killerzellen bindet und aktiviert. Ziel der vorliegenden Arbeit war es, die proteinchemischen Grundlagen für die Konstruktion eines humanisierten bispezifischen F(ab)2-Fragments zum Zweck der Tumortherapie refraktärer Hodgkin-Lymphome zu schaffen. Um die Antigene CD16 und CD30 in ausreichender Quantität und Qualität zu produzieren, wurden Vektoren für die Expression der extrazellulären Domänen als Fusionsproteine mit dem Strep-tag-Affinitätsanhängsel im Periplasma von E. coli konstruiert. Beim CD16-Antigen ließ sich auf diese Weise der die Aminosäuren 3-176 umfassende Bereich (CD16B) mit der kompletten extrazellulären Domäne mit Ausbeuten von 50 µg/L Kulturmedium (OD550 = 1) in löslicher Form gewinnen. Im Fall des CD30-Antigens mit seiner in zwei Subdomänen untergliederten extrazellulären Region wurde ein Fragment mit der C-terminalen Subdomäne (Aminosäuren 185-335; CD30A) für die gentechnische Herstellung ausgewählt, das sich mit Ausbeuten von 100 µg/L Kulturmedium (OD550 = 1) produzieren ließ. Mit Hilfe des Quadromantikörpers A9/HRS3 konnte sowohl im ELISA als auch mittels Oberflächenplasmon-Resonanzspektroskopie gezeigt werden, daß die rekombinanten Antigenfragmente CD16B und CD30A jeweils dasjenige Epitop trugen, welches vom entsprechenden Fab-Teil des bispezifischen Antikörpers erkannt wird. Ebenso wurde die spezifische Interaktion der in E. coli funktionell hergestellten chimären Fab-Fragmente muA9 und muHRS3c mit den entsprechenden rekombinanten Antigenfragmenten nachgewiesen und durch Gleichgewichtsanalyse folgende Dissoziationskonstanten ermittelt: muA9: 49.1 ± 2.8 nM; muHRS3c: 25.9 ± 2.8 nM. In guter Übereinstimmung dazu sind die aus der kinetischen Analyse ermittelten Dissoziationskonstanten. Die Auswertung der Kinetik ergab für die Komplexbildung aus dem muA9 Fab-Fragment und CD16B eine Geschwindigkeitskonstante kon von 2.4*105 M-1s-1 und für die Dissoziation eine koff von 1.5*10-2s-1, woraus sich eine Dissoziationskonstante von 63 nM errechnet. Für die Bildung des Komplexes aus dem muHRS3c Fab-Fragment und CD30A wurde eine kon von 8.6*104 M-1s-1 und für die Dissoziation eine koff von 2.0*10-3s-1 bestimmt, was eine Dissoziationskonstante von 24 nM ergab. Für die kovalente Kopplung zweier Fab-Fragmente zum F(ab)2-Fragment wurden zwei Sequenzmotive mit zwei bzw. einem freien Cysteinrest am C-Terminus der leichten Immunglobulinkette entwickelt. Mit Hilfe des Sequenzmotivs mit zwei freien Cysteinresten konnten die beiden Fab-Fragmente muA9 und muHRS3c über Disuldfidbrücken mit einer Kopplungsausbeute von 70 % zum F(ab)2-Fragment verknüpft werden. Im ersten Schritt dieses zweistufigen Kopplungsverfahrens wurden die freien Cysteinreste des muHRS3c Fab-Fragments in einer Thiol/Disulfidaustauschreaktion mit dem Ellman´s Reagenz DTNB derivatisiert. Nach Isolierung des entstandenen gemischten Disulfids wurde dieses mit dem muA9 Fab-Fragment in einer weiteren Thiol/Disulfidaustauschreaktion umgesetzt. Im Falle des Sequenzmotivs mit nur einem freien Cysteinrest gelang die Kopplung nach diesem Verfahren mit Ausbeuten von 55 %. Außerdem konnten zwei muHRS3c Fab-Fragmente mit zwei freien Cysteinresten über Thioetherbindungen mittels dem Linkerreagens o-Phenylendimaleimid regioselektiv mit Ausbeuten von 30-40 % zum bivalenten F(ab)2-Fragment gekoppelt werden. Um die Immunogenität der murinen variablen Domänen des Fab-Fragments zu reduzieren, wurde in dieser Arbeit der HRS-Antikörper mittels CDR-Transplantation humanisiert. Das resultierende humanisierte huHRS3 Fab-Fragment wurde in E. coli produziert und durch Metallchelat-Affinitätschromatographie gereinigt. Die mittels Oberflächenplasmon-Resonanzspektroskopie bestimmte Dissoziationskonstante war mit 278 ± 61 nM um Faktor 10 geringer war als die des zugrundeliegenden chimären muHRS3c Fab-Fragments. Die Untersuchung zur Ursache des Verlustes an Antigenaffinität anhand hybrid gepaarter variabler Domänen ergab, daß dieser Effekt hauptsächlich auf die humanisierte VH-Domäne zurückzuführen war. Diese wurde daher einer in vitro-Affinitätsmaturierung unterzogen. Mittels Error Prone PCR wurde eine huVH-Genbibiliothek mit Zufallsmutationen präpariert und diese in Form des rekombinanten Fab-Fragments im Kolonie-Filterstapel-Test auf verbesserte Bindung des markierten CD30A-Antigens durchmustert. Nach dreimaligem Durchlaufen des Affinitätsmaturierungszyklus wurde die Variante EP3/1 isoliert, welche insgesamt vier Aminosäuresubstitutionen zwei in FR-H3 und zwei in CDR-H3 aufwies. Im ELISA bzw. FACS zeigte diese Mutante ein nahezu identisches Bindungsverhalten an rekombinantes CD30A-Antigen bzw. CD30-positive L540 CY-Zellen wie das ursprüngliche chimäre muHRS3c Fab-Fragment. Die mittels Oberflächenplasmon-Resonanzspektroskopie für die Variante EP3/1 ermittelte Dissoziationskonstante nach der Gleichgewichtsanalyse betrug 58 ± 10 nM und war somit im Vergleich zum ursprünglich humanisierten HRS3 Fab-Fragment um den Faktor 5 verbessert. Die Auswertung der Kinetik ergab für die Komplexbildung eine Geschwindigkeitskonstante kon von 5.1*104 M-1s-1 und für die Dissoziation eine koff von 2.0*10-3 s-1, woraus sich eine Dissoziationskonstante von 40 nM errechnet. Damit sind die Voraussetzungen geschaffen, um in Kombination mit einem humanisierten anti-CD16 Fab-Fragment ein vollständig humanisiertes bispezifisches anti-CD16/anti-CD30 F(ab)2-Fragment in ausreichenden Mengen zu ökonomischen Bedingungen für Tierversuche und spätere therapeutische Anwendungen bereitzustellen. In the last few years the immunotherapy of tumour diseases with bispecific F(ab)2 fragments became more and more interesting. Especially the strategy of activating cytotoxic effector cells by crosslinking them with tumour cells via the tumour associated antigen is promising. For example, this method can be used to therapy the Hodgkin lymphoma disease. Then, one arm of the bispecific construct, the Fab fragment HRS3, binds to the CD30 on lymphatic tumour cells, and the other, the A9 Fab fragment, binds to the Fc-gamma receptor III on natural killer cells and activates them. The aim of this thesis was the development of the proteinchemical basis for the construction of a humanized bispecific F(ab)2 fragment for immunotherapy of the Hodgkin lymphoma disease. To produce the antigens CD16 and CD30 in sufficient quantity and quality in E. coli vectors for the periplasmic expression of the extracellular domains as fusion proteins with the Strep-tag were constructed. Regarding the CD16 antigen the region with the amino acids 3-176 (CD16B) with nearly the complete extracellular domain could be isolated in soluble form with yields of 50 µg/L culture (OD550=1). In the case of the CD30 antigen with its extracellular domain divided in two subdomains a fragment with the C-terminal subdomain (amino acids 185-335; CD30A) was chosen for production. The yield was 100 µg/L culture (OD550=1). The binding of the original bispecific anti-CD16/anti-CD30 (A9/HRS3) monoclonal mouse antibody to the recombinant antigens CD16B and CD30A revealed that they carried the epitope recognized by the corresponding Fab-part of the bispecific A9/HRS3 monoclonal mouse antibody. Also, the specific interaction of the chimaeric Fab fragments muA9 and muHRS3c that were produced in E. coli could be detected. Following dissociation constants were determined by equilibrium analysis using surface plasmon resonance spectroscopy: muA9: 49.1 ± 2.8 nM, muHRS3c: 25.9 ± 2.8 nM. In good agreement to these are the dissociation constants from the kinetic analysis. For the formation of the complex between the chimaeric muA9 Fab fragment and CD16B the kinetic association constant kon was 2.4*105 M-1s-1, whereas the kinetic dissociation constant koff was 1.5*10-2s-1, yielding a dissociation constant of 63 nM. For the formation of the complex between the chimaeric muHRS3c Fab fragment and CD30A kon was 8.6*104 M-1s-1 and for the dissociation koff was 2.0*10-3s-1, resulting in a dissociation constant of 24 nM. For covalently coupling two Fab fragments to a F(ab)2 fragment two sequence motifs with one or two free cysteine residues at the C-terminus of the light chain were developed. Using the sequence motif with two free cysteine residues the two chimaeric Fab fragments muA9 and muHRS3c could be linked via disulfid bonds. The coupling efficiency was about 70 %. In the first step of this two-step coupling procedure the free cysteine residues of the chimaeric muHRS3c Fab fragment were reacted with Ellman´s Reagent DTNB in a thiol/disulfid exchange reaction. After isolation of the produced mixed disulfid it was reacted with the muA9 Fab fragment in a second thiol/disulfid exchange reaction. In the case of the sequence motif with only one free cysteine residue the coupling efficiency was about 55 %. Moreover, two chimaeric muHRS3c Fab fragments with two free cysteine residues could be linked to a bivalent F(ab)2 fragment via thioether bonds using the chemical linker o-phenylendimaleimide. The coupling efficiency was about 30-40 %. To reduce the immunogenicity of the murine variable domains the chimaeric muHRS3 Fab fragment was humanized by CDR grafting. The resulting humanized huHRS3 Fab fragment was produced in E. coli and purified by metal-chelat affinity chromatography. The dissociation constant determined by using surface plasmon resonance spectroscopy was 278 ± 61 nM and therefore a factor ten lower than for the original chimaeric muHRS3c Fab fragment. The analysis of the decrease in affinity revealed that this effect was mainly due to the humanized VH domain. Therefore, this domain was affinity maturated. Using error prone PCR a huVH gene library with random mutations was prepared. The corresponding Fab fragments were screened for improved binding towards CD30A antigen using a filter sandwich colony screening assay. After three rounds of this affinity maturation cycle the variant EP3/1 could be isolated. It contained four amino acid substitutions, of which two were in FR-H3 and two in CDR-H3. In ELISA and FACS this mutant revealed nearly identical binding towards recombinant CD30A antigen and CD30+ L540 CY-cells as the original chimaeric muHRS3c Fab fragment, respectively. The dissociation constant for the variant EP3/1 determined by equilibrium analysis was 58 ± 10 nM. Compared to the original humanized HRS3 Fab fragment the affinity could be improved by a factor of five. The kinetic analysis revealed for the complex formation a kinetic association constant kon = 5.1*104 M-1s-1 and for the complex dissociation a kinetic dissociation constant koff = 2.0*10-3 s-1, revealing a dissociation constant of 40 nM. Now, in combination with a humanized anti-CD16 Fab fragment a completely humanized bispecific anti-CD16/anti-CD30 F(ab)2 fragment can be produced in a sufficient amount for further studies.
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- 2005
31. Neutralizing Inhibition of Neuronal Regeneration in the CNS
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Fiedler, Markus, Skerra, A. (Univ. Prof. Dr.), Skerra, A., Univ (Prof. Dr.), and Langosch, D., Univ (Prof. Dr.)
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Nogo-A ,IN-1 ,Affinitäts-Maturierung ,axonale Regeneration ,bakterielle Proteinproduktion ,neuronaler Inhibitor ,Zufalls-Mutagenese ,Antikörper Engineering ,TAC ,IMAC ,metabolische Selektion ,Biowissenschaften, Biologie ,ddc:570 ,affinity maturation ,axonal regeneration ,bacterial expression ,neuronal inhibitor ,random mutagenesis ,antibody engineering ,metabolic selection - Abstract
Axone werden im ZNS von Wirbeltieren durch das Neuronale Inhibitorprotein Nogo-A aktiv am Aussprossen gehindert. Dies beschränkt die Plastizität des adulten ZNS, verhindert allerdings im Fall einer Läsion auch maßgeblich die neuronale Regeneration. Der mono-klonale Antikörper IN-1 (IgM/k) neutralisiert die inhibitorische Wirkung von Nogo-A und ermöglicht so die axonale Regeneration im ZNS. In der vorliegenden Arbeit wurden Methoden zur Herstellung und Optimierung rekombinanter Fragmente des Antikörpers IN-1 sowie des neuronalen Inhibitors Nogo-A mittels Protein-Engineering einschließlich der Analyse ihrer Wechselwirkung entwickelt. Auf diese Weise wurden schließlich in vitro im Gegensatz zu konventionellen Immunisierungsversuchen Antikörper mit verbesserter Affinität und neutralisierender Aktivität erhalten. Für den IN-1 Antikörper wurde zunächst die bakterielle Produktion eines chimären Fab-Fragmentes im Fermenter-Maßstab soweit verbessert, daß es in ausreichender Menge für Zellkultur- und Tierexperimente zur Verfügung stand. Hierzu wurde eine vektorvermittelte Komplementierung der chromosomalen proBA-Deletion des prolin-auxotrophen E. coli K12-Stamms JM83 realisiert. Diese ermöglichte die Nutzung des überlegenen Sekretionsverhaltens von JM83 bei der Fermentation in einem Minimalmedium und führte zur Stabilisierung des Expressionsvektors durch den zusätzlichen metabolischen Selektionsdruck. Das chimäre IN-1 Fab-Fragment, dessen Ausbeute mit diesem Verfahren im Vergleich zu vorherigen Experimenten vervierfacht wurde, wurde mittels IMAC gereinigt und für Regenerations-Experimente verwendet. Im Zusammenhang mit der Behandlung von Rückenmarksläsionen bei Ratten konnte mit dem IN-1 Fab-Fragment eine signifikante Regeneration von verletzten zentralnervösen Neuronen erreicht werden. Auf der Grundlage des rekombinanten Wildtyp IN-1 Fab-Fragments wurde zudem die Reini-gung mittels der Thiophilen Adsorptionschromatographie etabliert. Dabei wurde das Fab-Fragment unabhängig von einem Affinitätsanhängsel (His6- oder Strep-Tag) in einem Schritt als löslicher Heterodimer aus der periplasmatischen Proteinfraktion von E. coli isoliert. Insbesonders für eine eventuelle therapeutische Anwendung von optimierten Varianten des IN-1 Fab-Fragments ist der Verzicht auf Affinitätsanhängsel vorteilhaft. Die vermutlich extrazelluläre und inhibitorisch aktive Domäne von Nogo-A wurde als lösliches Protein in E. coli hergestellt und durch Streptavidin-Affinitätschromatographie gereinigt. Das erhaltene Fragment NiFr2 war inhibitorisch aktiv und bildete die Grundlage für die In vitro-Affinitätsmaturierung des Antikörpers IN-1. Durch Herstellung eines rekombinanten Nogo-A Fragments (NiFr4) mit einem Strep-Tag sowie einem His6-Tag an den beiden Termini, welches durch IMAC und Streptavidin-Affinitätschromatographie gereinigt wurde, konnten Reinheit und Homogenität der Präparationen im Vergleich zu NiFr2 maßgeblich verbessert werden. Dies war die Grundlage für den erstmaligen Nachweis der Antigen/Antikörper-Komplexbildung aus Nogo-A und dem IN-1 Fab-Fragment mit Hilfe der Oberflächenplasmonresonanz-Spektroskopie. Bis zu Beginn der vorliegenden Arbeit war es aufgrund der geringen Affinität von IN-1 gegenüber dem vermuteten Antigen nicht gelungen, die direkte Bindung des Antikörpers an natives oder rekombinantes Nogo-A mit immunchemischen Methoden nachzuweisen und damit auf molekularer Ebene zu begründen. Ausgehend von dem IN-1 Fab-Fragment wurde daher ein Verfahren zur Affinitätsmaturierung bezüglich Nogo-A etabliert. Durch wiederholte Zyklen von ortsgerichteter Zufallsmutagenese und Durchmusterung der resultierenden Molekülbibliothek mit Hilfe eines Filterstapel-Tests auf verbesserte Bindung von NiFr2 wurde die Mutante II.1.8 des IN-1 Fab-Fragments erhalten. Das II.1.8 Fab-Fragment weist im Vergleich zu IN-1 insgesamt fünf Aminosäure-Substitutionen innerhalb von CDR-L3 auf und zeigt nachweisbare Bindung an natives Nogo-A bzw. an seine bakteriell produzierten Fragmente im ELISA. Die Dissoziationskonstante des Komplexes aus dem II.1.8 Fab-Fragment und NiFr4 wurde durch Oberflächenplasmonresonanz-Spektroskopie mit 1 µM bestimmt. Das Wildtyp IN-1 Fab-Fragment zeigte unter denselben Bedingungen eine achtfach schlechtere Affinität. Damit wurde erstmals mit immunchemischen Methoden demonstriert, daß es sich bei dem Produkt des Nogo-A-Gens um das Antigen des Antikörpers IN-1 handelt. Im Gegensatz zum Wildtyp IN-1 wurden durch Verwendung des II.1.8 Fab-Fragments bei immunhistochemischen Experimenten myelinreiche Regionen im Hirn und Rückenmark der Ratte spezifisch angefärbt. Darüber hinaus zeigte das II.1.8 Fab-Fragment in Zellkultur-Experimenten eine konzentrationsabhängige neutralisierende Aktivität gegenüber der inhibitorischen Wirkung von Nogo-A, die deutlich über der des IN-1 Fab-Fragments lag. Damit wurde der Zusammenhang zwischen einer verbesserten proteinchemischen Bindung von Nogo-A durch das optimierte IN-1 Fab-Fragment und einer erhöhten neutralisierenden Aktivität gezeigt. Für eine mögliche therapeutische Anwendung von Nogo-A-bindenden rekombinanten Fab-Fragmenten wurden die variablen Domänen des II.1.8 Fab-Fragments humanisiert. Dazu wurden dessen CDRs auf die Gerüststruktur der variablen Domänen des humanen Anti-Thyroidperoxidase-Antikörpers TR1.9 übertragen. Das resultierende humII.1.8 Fab-Fragment wurde in E. coli produziert und mittels IMAC gereinigt. In ELISA-Experimenten wurde der Erhalt der Bindungsaktivität des humanisierten Fab-Fragments gegenüber dem rekombinanten Nogo-A Fragment NiFr2 nachgewiesen. Schließlich wurde die bakterielle Produktion von neuartigen Fusionsproteinen aus einem Fab-Fragment und dem Enzym TEM1 b-Lactamase etabliert. Deren bifunktionelle Eigenschaften im Hinblick auf die Antigenbindung und die Reporteraktivität wurden durch ELISA sowie enzymkinetische Experimente nachgewiesen. Damit wurde eine Grundlage für die Ver-wendung ähnlicher Fusionsproteine für diagnostische oder auch therapeutische Anwendungen geschaffen. The outgrowth of axons in the CNS of higher vertebrates is strongly restricted by the neuronal inhibitor protein Nogo-A leading to limited plasticity and the lack of neuronal regeneration after lesions. The inhibitory activity of Nogo-A can be neutralized by application of the monoclonal antibody IN-1 (IgM/k) which enables neuronal outgrowth and regeneration in the CNS. In this work the production and optimization of recombinant fragments of IN-1 and Nogo-A is described including the detection and analysis of their interaction in vitro. In contrast to conventional immunization experiments by the approach realized in this work it was possible to obtain antibodies with improved affinity and neutralizing activity. In a first step the high-scale production of a partially humanized (chimeric) IN-1 Fab-fragment was optimised allowing cell culture and in vivo experiments. Therefore the proline-auxotrophic Escherichia coli K12 strain JM83 harboring a newly constructed expression vector providing the proBA gene in trans was utilized for the production of the IN-1 Fab-fragment in a fermentor. The plasmid mediated complementation of the chromosomal proBA deletion abolished plasmid-loss observed in earlier experiments and enabled the utilization of JM83 as an expression strain with approved periplasmic protein secretion characteristics in the presence of minimal media. Using this strategy the yield of the chimeric IN-1 Fab-fragment could be improved by the factor of four. The obtained Fab-fragment was used for experiments in vivo and led to a significant regeneration of injured neurons in the spinal cord of adult rats. Furthermore, based on the chimeric IN-1 Fab-fragment an alternative purification procedure utilizing thiophilic adsorption chromatography (TAC) was established. By this way the Fab-fragment was isolated in one step from the periplasmic protein fraction of E. coli without the need for an affinity tag (e. g. His6- or Strep-Tag). This method should prove valuable in case of a therapeutic application of the IN-1 Fab-fragment when the presence of affinity tags might not be feasible. The putative extracellular domain of Nogo-A which is thought to carry its inhibitory activity was produced as a soluble protein in E. coli and purified by Streptavidin (SA) affinity chromatography. The obtained fragment NiFr2 revealed inhibitory activity and was used for in vitro affinity maturation of the antibody IN-1. In order to improve purity and homogeneity of the target protein a recombinant Nogo-A fragment (NiFr4) which carried a His6 tag in addition to the Strep-Tag was produced and purified by consecutive IMAC and SA affinity chromatography. Using NiFr4 in surface plasmon resonance spectroscopy it was possible to detect and analyze the formation of the antigen/antibody complex of Nogo-A and IN-1 for the first time. Due to the low antigen affinity of the IN-1 antibody it had not been possible to detect its binding to native or recombinant Nogo-A by conventional immunoassays until the begin of this work. Therefore a method for an in vitro affinity maturation concerning Nogo-A was established starting from the chimeric IN-1 Fab-fragment. After repeated cycles of site-directed random mutagenesis and screening the mutant II.1.8 of the IN-1 Fab-fragment was obtained carrying five side chain substitutions within CDR-L3 and showing detectable binding to native and recombinant Nogo-A in ELISA experiments. The dissociation constant for the complex with NiFr4 was determined in surface plasmon resonance measurements as approximately 1 µM. The affinity of the non-mutated IN-1 Fab-fragment was 8-fold lower. This proved for the first time that Nogo-A represents the antigen of the antibody IN-1. In contrast to the IN-1 Fab-fragment the engineered Fab-fragment appeared to be well suited for the specific detection of Nogo-A in immunochemical assays and for the histochemical staining of myelin-rich tissue sections. Most importantly, its concentration-dependent neutralizing effect on the Nogo-A inhibitory activity was significantly enhanced in cell culture. These experiments revealed the coherence between improved binding affinity to Nogo-A and the enhanced biological activity in the context of inhibitor neutralization in the CNS. As a further step to the therapeutic application of Nogo-A binding recombinant Fab-fragments in near future the variable domains of the II.1.8 Fab-fragment were humanized by CDR-grafting. The resulting humII.1.8 Fab-fragment was produced in E. coli, purified by IMAC and showed a detectable binding to recombinant Nogo-A fragments in ELISA. Finally, the bacterial production of fusion proteins constituted of an Fab-fragment and the enzyme TEM1 b-lactamase was established. The (bi-)functionality of this construct concerning antigen-binding and reporter activity was proven by ELISA and enzyme kinetic experiments. This new type of fusion proteins might serve as diagnostic or therapeutic tools in the future.
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- 2005
32. Cleavage efficiency of the intramembrane protease γ-secretase is reduced by the palmitoylation of a substrate's transmembrane domain.
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Aßfalg M, Güner G, Müller SA, Breimann S, Langosch D, Muhle-Goll C, Frishman D, Steiner H, and Lichtenthaler SF
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- Membrane Proteins metabolism, Protein Domains, Protein Processing, Post-Translational, Amyloid beta-Protein Precursor metabolism, Amyloid Precursor Protein Secretases genetics, Amyloid Precursor Protein Secretases metabolism, Lipoylation
- Abstract
The intramembrane protease γ-secretase has broad physiological functions, but also contributes to Notch-dependent tumors and Alzheimer's disease. While γ-secretase cleaves numerous membrane proteins, only few nonsubstrates are known. Thus, a fundamental open question is how γ-secretase distinguishes substrates from nonsubstrates and whether sequence-based features or post-translational modifications of membrane proteins contribute to substrate recognition. Using mass spectrometry-based proteomics, we identified several type I membrane proteins with short ectodomains that were inefficiently or not cleaved by γ-secretase, including 'pituitary tumor-transforming gene 1-interacting protein' (PTTG1IP). To analyze the mechanism preventing cleavage of these putative nonsubstrates, we used the validated substrate FN14 as a backbone and replaced its transmembrane domain (TMD), where γ-cleavage occurs, with the one of nonsubstrates. Surprisingly, some nonsubstrate TMDs were efficiently cleaved in the FN14 backbone, demonstrating that a cleavable TMD is necessary, but not sufficient for cleavage by γ-secretase. Cleavage efficiencies varied by up to 200-fold. Other TMDs, including that of PTTG1IP, were still barely cleaved within the FN14 backbone. Pharmacological and mutational experiments revealed that the PTTG1IP TMD is palmitoylated, which prevented cleavage by γ-secretase. We conclude that the TMD sequence of a membrane protein and its palmitoylation can be key factors determining substrate recognition and cleavage efficiency by γ-secretase., (© 2024 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)
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- 2024
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33. Interaction of Substrates with γ-Secretase at the Level of Individual Transmembrane Helices-A Methodological Approach.
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Pauli TM, Julius A, Costa F, Eschrig S, Moosmüller J, Fischer L, Schanzenbach C, Schmidt FC, Ortner M, and Langosch D
- Abstract
Intramembrane proteases, such as γ secretase, typically recruit multiple substrates from an excess of single-span membrane proteins. It is currently unclear to which extent substrate recognition depends on specific interactions of their transmembrane domains (TMDs) with TMDs of a protease. Here, we investigated a large number of potential pairwise interactions between TMDs of γ secretase and a diverse set of its substrates using two different configurations of BLaTM, a genetic reporter system. Our results reveal significant interactions between TMD2 of presenilin, the enzymatic subunit of γ secretase, and the TMD of the amyloid precursor protein, as well as of several other substrates. Presenilin TMD2 is a prime candidate for substrate recruitment, as has been shown from previous studies. In addition, the amyloid precursor protein TMD enters interactions with presenilin TMD 4 as well as with the TMD of nicastrin. Interestingly, the Gly-rich interfaces between the amyloid precursor protein TMD and presenilin TMDs 2 and 4 are highly similar to its homodimerization interface. In terms of methodology, the economics of the newly developed library-based method could prove to be a useful feature in related future work for identifying heterotypic TMD-TMD interactions within other biological contexts.
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- 2023
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34. Permissive Conformations of a Transmembrane Helix Allow Intramembrane Proteolysis by γ-Secretase.
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Ortner M, Guschtschin-Schmidt N, Stelzer W, Muhle-Goll C, and Langosch D
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- Models, Molecular, Mutation, Protein Domains, Amyloid Precursor Protein Secretases chemistry, Proteolysis
- Abstract
The intramembrane protease γ-secretase activates important signaling molecules, such as Notch receptors. It is still unclear, however, how different elements within the primary structure of substrate transmembrane domains (TMDs) contribute to their cleavability. Using a newly developed yeast-based cleavage assay, we identified three crucial regions within the TMDs of the paralogs Notch1 and Notch3 by mutational and gain-of-function approaches. The AAAA or AGAV motifs within the N-terminal half of the TMDs were found to confer strong conformational flexibility to these TMD helices, as determined by mutagenesis coupled to deuterium/hydrogen exchange. Crucial amino acids within the C-terminal half may support substrate docking into the catalytic cleft of presenilin, the enzymatic subunit of γ-secretase. Further, residues close to the C-termini of the TMDs may stabilize a tripartite β-sheet in the substrate/enzyme complex. NMR structures reveal different extents of helix bending as well as an ability to adopt widely differing conformational substates, depending on the sequence of the N-terminal half. The difference in cleavability between Notch1 and Notch3 TMDs is jointly determined by the conformational repertoires of the TMD helices and the sequences of the C-terminal half, as suggested by mutagenesis and building molecular models. In sum, cleavability of a γ-secretase substrate is enabled by different functions of cooperating TMD regions, which deepens our mechanistic understanding of substrate/non-substrate discrimination in intramembrane proteolysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)
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- 2023
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35. Different transmembrane domains determine the specificity and efficiency of the cleavage activity of the γ-secretase subunit presenilin.
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Schmidt FC, Fitz K, Feilen LP, Okochi M, Steiner H, and Langosch D
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- Humans, Alzheimer Disease metabolism, Amyloid beta-Peptides genetics, Amyloid beta-Peptides metabolism, Amyloid beta-Protein Precursor metabolism, Protein Domains, Amyloid Precursor Protein Secretases genetics, Amyloid Precursor Protein Secretases metabolism, Presenilin-1 chemistry, Presenilin-1 genetics, Presenilin-1 metabolism, Presenilin-2 chemistry, Presenilin-2 genetics, Presenilin-2 metabolism
- Abstract
The γ-secretase complex catalyzes the intramembrane cleavage of C99, a carboxy-terminal fragment of the amyloid precursor protein. Two paralogs of its catalytic subunit presenilin (PS1 and PS2) are expressed which are autocatalytically cleaved into an N-terminal and a C-terminal fragment during maturation of γ-secretase. In this study, we compared the efficiency and specificity of C99 cleavage by PS1- and PS2-containing γ-secretases. Mass spectrometric analysis of cleavage products obtained in cell-free and cell-based assays revealed that the previously described lower amyloid-β (Aβ)38 generation by PS2 is accompanied by a reciprocal increase in Aβ37 production. We further found PS1 and PS2 to show different preferences in the choice of the initial cleavage site of C99. However, the differences in Aβ38 and Aβ37 generation appear to mainly result from altered subsequent stepwise cleavage of Aβ peptides. Apart from these differences in cleavage specificity, we confirmed a lower efficiency of initial C99 cleavage by PS2 using a detergent-solubilized γ-secretase system. By investigating chimeric PS1/2 molecules, we show that the membrane-embedded, nonconserved residues of the N-terminal fragment mainly account for the differential cleavage efficiency and specificity of both presenilins. At the level of individual transmembrane domains (TMDs), TMD3 was identified as a major modulator of initial cleavage site specificity. The efficiency of endoproteolysis strongly depends on nonconserved TMD6 residues at the interface to TMD2, i.e., at a putative gate of substrate entry. Taken together, our results highlight the role of individual presenilin TMDs in the cleavage of C99 and the generation of Aβ peptides., Competing Interests: Conflict of interest The authors declare they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2023
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36. Cooperation of N- and C-terminal substrate transmembrane domain segments in intramembrane proteolysis by γ-secretase.
- Author
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Werner NT, Högel P, Güner G, Stelzer W, Wozny M, Aßfalg M, Lichtenthaler SF, Steiner H, and Langosch D
- Subjects
- Proteolysis, Protein Domains, Catalytic Domain, Amyloid Precursor Protein Secretases genetics, Amyloid Precursor Protein Secretases metabolism, Amyloid beta-Protein Precursor genetics, Amyloid beta-Protein Precursor metabolism
- Abstract
Intramembrane proteases play a pivotal role in biology and medicine, but how these proteases decode cleavability of a substrate transmembrane (TM) domain remains unclear. Here, we study the role of conformational flexibility of a TM domain, as determined by deuterium/hydrogen exchange, on substrate cleavability by γ-secretase in vitro and in cellulo. By comparing hybrid TMDs based on the natural amyloid precursor protein TM domain and an artificial poly-Leu non-substrate, we find that substrate cleavage requires conformational flexibility within the N-terminal half of the TMD helix (TM-N). Robust cleavability also requires the C-terminal TM sequence (TM-C) containing substrate cleavage sites. Since flexibility of TM-C does not correlate with cleavage efficiency, the role of the TM-C may be defined mainly by its ability to form a cleavage-competent state near the active site, together with parts of presenilin, the enzymatic component of γ-secretase. In sum, cleavability of a γ-secretase substrate appears to depend on cooperating TM domain segments, which deepens our mechanistic understanding of intramembrane proteolysis., (© 2023. The Author(s).)
- Published
- 2023
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37. Helical stability of the GnTV transmembrane domain impacts on SPPL3 dependent cleavage.
- Author
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Papadopoulou AA, Stelzer W, Silber M, Schlosser C, Spitz C, Haug-Kröper M, Straub T, Müller SA, Lichtenthaler SF, Muhle-Goll C, Langosch D, and Fluhrer R
- Subjects
- Golgi Apparatus metabolism, Glycosylation, Polysaccharides metabolism, Aspartic Acid Endopeptidases metabolism, Membrane Proteins genetics, Membrane Proteins metabolism
- Abstract
Signal-Peptide Peptidase Like-3 (SPPL3) is an intramembrane cleaving aspartyl protease that causes secretion of extracellular domains from type-II transmembrane proteins. Numerous Golgi-localized glycosidases and glucosyltransferases have been identified as physiological SPPL3 substrates. By SPPL3 dependent processing, glycan-transferring enzymes are deactivated inside the cell, as their active site-containing domain is cleaved and secreted. Thus, SPPL3 impacts on glycan patterns of many cellular and secreted proteins and can regulate protein glycosylation. However, the characteristics that make a substrate a favourable candidate for SPPL3-dependent cleavage remain unknown. To gain insights into substrate requirements, we investigated the function of a GxxxG motif located in the transmembrane domain of N-acetylglucosaminyltransferase V (GnTV), a well-known SPPL3 substrate. SPPL3-dependent secretion of the substrate's ectodomain was affected by mutations disrupting the GxxxG motif. Using deuterium/hydrogen exchange and NMR spectroscopy, we studied the effect of these mutations on the helix flexibility of the GnTV transmembrane domain and observed that increased flexibility facilitates SPPL3-dependent shedding and vice versa. This study provides first insights into the characteristics of SPPL3 substrates, combining molecular biology, biochemistry, and biophysical techniques and its results will provide the basis for better understanding the characteristics of SPPL3 substrates with implications for the substrates of other intramembrane proteases., (© 2022. The Author(s).)
- Published
- 2022
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38. Proteolytically generated soluble Tweak Receptor Fn14 is a blood biomarker for γ-secretase activity.
- Author
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Güner G, Aßfalg M, Zhao K, Dreyer T, Lahiri S, Lo Y, Slivinschi BI, Imhof A, Jocher G, Strohm L, Behrends C, Langosch D, Bronger H, Nimsky C, Bartsch JW, Riddell SR, Steiner H, and Lichtenthaler SF
- Subjects
- Animals, Biomarkers, Cytokine TWEAK, Humans, Ligands, Mice, Receptors, Cell Surface metabolism, Receptors, Tumor Necrosis Factor metabolism, TWEAK Receptor, Tumor Necrosis Factor-alpha, Amyloid Precursor Protein Secretases, Receptors, Chimeric Antigen
- Abstract
Fn14 is a cell surface receptor with key functions in tissue homeostasis and injury but is also linked to chronic diseases. Despite its physiological and medical importance, the regulation of Fn14 signaling and turnover is only partly understood. Here, we demonstrate that Fn14 is cleaved within its transmembrane domain by the protease γ-secretase, resulting in secretion of the soluble Fn14 ectodomain (sFn14). Inhibition of γ-secretase in tumor cells reduced sFn14 secretion, increased full-length Fn14 at the cell surface, and enhanced TWEAK ligand-stimulated Fn14 signaling through the NFκB pathway, which led to enhanced release of the cytokine tumor necrosis factor. γ-Secretase-dependent sFn14 release was also detected ex vivo in primary tumor cells from glioblastoma patients, in mouse and human plasma and was strongly reduced in blood from human cancer patients dosed with a γ-secretase inhibitor prior to chimeric antigen receptor (CAR)-T-cell treatment. Taken together, our study demonstrates a novel function for γ-secretase in attenuating TWEAK/Fn14 signaling and suggests the use of sFn14 as an easily measurable pharmacodynamic biomarker to monitor γ-secretase activity in vivo., (© 2022 The Authors. Published under the terms of the CC BY 4.0 license.)
- Published
- 2022
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39. Site-Specific Fragmentation of Green Fluorescent Protein Induced by Blue Light.
- Author
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Heckmeier PJ and Langosch D
- Subjects
- Amino Acid Sequence, Color, Fluorescence, Mass Spectrometry, Peptide Fragments chemistry, Green Fluorescent Proteins chemistry, Green Fluorescent Proteins radiation effects, Light, Proteolysis radiation effects
- Abstract
Green fluorescent protein (GFP) and related fluorescent proteins have multiple applications in cell biology, and elucidating their functions has been at the focus of biophysical research for about three decades. Fluorescent proteins can be bleached by intense irradiation, and a number of them undergo photoconversion. Rare cases have been reported where distant functional relatives of GFP exhibit UV-light-induced protein fragmentation. Here, we show that irreversible bleaching of two different variants of GFP (sfGFP, EGFP) with visible light is paralleled by successive backbone fragmentation of the protein. Mass spectrometry revealed that the site of fragmentation resides at the fluorophore, between residue positions 65 and 66.
- Published
- 2021
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40. Non-canonical Shedding of TNFα by SPPL2a Is Determined by the Conformational Flexibility of Its Transmembrane Helix.
- Author
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Spitz C, Schlosser C, Guschtschin-Schmidt N, Stelzer W, Menig S, Götz A, Haug-Kröper M, Scharnagl C, Langosch D, Muhle-Goll C, and Fluhrer R
- Abstract
Ectodomain (EC) shedding defines the proteolytic removal of a membrane protein EC and acts as an important molecular switch in signaling and other cellular processes. Using tumor necrosis factor (TNF)α as a model substrate, we identify a non-canonical shedding activity of SPPL2a, an intramembrane cleaving aspartyl protease of the GxGD type. Proline insertions in the TNFα transmembrane (TM) helix strongly increased SPPL2a non-canonical shedding, while leucine mutations decreased this cleavage. Using biophysical and structural analysis, as well as molecular dynamic simulations, we identified a flexible region in the center of the TNFα wildtype TM domain, which plays an important role in the processing of TNFα by SPPL2a. This study combines molecular biology, biochemistry, and biophysics to provide insights into the dynamic architecture of a substrate's TM helix and its impact on non-canonical shedding. Thus, these data will provide the basis to identify further physiological substrates of non-canonical shedding in the future., Competing Interests: The authors declare no competing interests., (© 2020 The Authors.)
- Published
- 2020
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41. Light-induced lipid mixing implies a causal role of lipid splay in membrane fusion.
- Author
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Scheidt HA, Kolocaj K, Konrad DB, Frank JA, Trauner D, Langosch D, and Huster D
- Subjects
- Lipid Bilayers chemistry, Membrane Fusion, Models, Chemical
- Abstract
The fusion of lipid membranes is central to many biological processes and requires substantial structural reorganization of lipids brought about by the action of fusogenic proteins. Previous molecular dynamics simulations have suggested that splayed lipids, whose tails transiently contact the headgroup region of the bilayer, initiate lipid mixing. Here, we explore the lipid splay hypothesis experimentally. We show that the light-induced trans/cis conversion of the azobenzene-based tail of a model lipid molecule enhances the probability by which its own acyl chains, or the acyl chains of the host lipid, transiently contact the lipid headgroup in a liposomal bilayer. At the same time, the trans/cis conversion triggers lipid mixing of sonicated or extruded liposomes, without requiring fusogenic proteins. This establishes a causal relationship between lipid splay and membrane fusion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)
- Published
- 2020
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42. Experimental determination and data-driven prediction of homotypic transmembrane domain interfaces.
- Author
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Xiao Y, Zeng B, Berner N, Frishman D, Langosch D, and Teese MG
- Abstract
Interactions between their transmembrane domains (TMDs) frequently support the assembly of single-pass membrane proteins to non-covalent complexes. Yet, the TMD-TMD interactome remains largely uncharted. With a view to predicting homotypic TMD-TMD interfaces from primary structure, we performed a systematic analysis of their physical and evolutionary properties. To this end, we generated a dataset of 50 self-interacting TMDs. This dataset contains interfaces of nine TMDs from bitopic human proteins (Ire1, Armcx6, Tie1, ATP1B1, PTPRO, PTPRU, PTPRG, DDR1, and Siglec7) that were experimentally identified here and combined with literature data. We show that interfacial residues of these homotypic TMD-TMD interfaces tend to be more conserved, coevolved and polar than non-interfacial residues. Further, we suggest for the first time that interface positions are deficient in β-branched residues, and likely to be located deep in the hydrophobic core of the membrane. Overrepresentation of the GxxxG motif at interfaces is strong, but that of (small)xxx(small) motifs is weak. The multiplicity of these features and the individual character of TMD-TMD interfaces, as uncovered here, prompted us to train a machine learning algorithm. The resulting prediction method, THOIPA (www.thoipa.org), excels in the prediction of key interface residues from evolutionary sequence data., (© 2020 The Author(s).)
- Published
- 2020
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- View/download PDF
43. Determining the Stoichiometry of Small Protein Oligomers Using Steady-State Fluorescence Anisotropy.
- Author
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Heckmeier PJ, Agam G, Teese MG, Hoyer M, Stehle R, Lamb DC, and Langosch D
- Subjects
- Anisotropy, Fluorescence Polarization, Green Fluorescent Proteins genetics, Photobleaching, Fluorescence Resonance Energy Transfer
- Abstract
A large fraction of soluble and membrane-bound proteins exists as non-covalent dimers, trimers, and higher-order oligomers. The experimental determination of the oligomeric state or stoichiometry of proteins remains a nontrivial challenge. In one approach, the protein of interest is genetically fused to green fluorescent protein (GFP). If a fusion protein assembles into a non-covalent oligomeric complex, exciting their GFP moiety with polarized fluorescent light elicits homotypic Förster resonance energy transfer (homo-FRET), in which the emitted radiation is partially depolarized. Fluorescence depolarization is associated with a decrease in fluorescence anisotropy that can be exploited to calculate the oligomeric state. In a classical approach, several parameters obtained through time-resolved and steady-state anisotropy measurements are required for determining the stoichiometry of the oligomers. Here, we examined novel approaches in which time-resolved measurements of reference proteins provide the parameters that can be used to interpret the less expensive steady-state anisotropy data of candidates. In one approach, we find that using average homo-FRET rates (k
FRET ), average fluorescence lifetimes (τ), and average anisotropies of those fluorophores that are indirectly excited by homo-FRET (rET ) do not compromise the accuracy of calculated stoichiometries. In the other approach, fractional photobleaching of reference oligomers provides a novel parameter a whose dependence on stoichiometry allows one to quantitatively interpret the increase of fluorescence anisotropy seen after photobleaching the candidates. These methods can at least reliably distinguish monomers from dimers and trimers., (Copyright © 2020 Biophysical Society. Published by Elsevier Inc. All rights reserved.)- Published
- 2020
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- View/download PDF
44. Author Correction: Identifying ionic interactions within a membrane using BLaTM, a genetic tool to measure homo- and heterotypic transmembrane helix-helix interactions.
- Author
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Schanzenbach C, Schmidt FC, Breckner P, Teese MG, and Langosch D
- Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Published
- 2020
- Full Text
- View/download PDF
45. Corrigendum to 'BLaTM 2.0, a Genetic Tool Revealing Preferred Antiparallel Interaction of Transmembrane Helix 4 of the Dual-Topology Protein EmrE' [Journal of Molecular Biology 11 (2017) 1630-1637].
- Author
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Julius A, Laur L, Schanzenbach C, and Langosch D
- Published
- 2020
- Full Text
- View/download PDF
46. Conformationally Flexible Sites within the Transmembrane Helices of Amyloid Precursor Protein and Notch1 Receptor.
- Author
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Stelzer W and Langosch D
- Subjects
- Amino Acid Sequence, Amyloid beta-Protein Precursor genetics, Peptide Fragments genetics, Protein Conformation, Protein Domains genetics, Protein Structure, Secondary, Receptor, Notch1 genetics, Amyloid beta-Protein Precursor chemistry, Peptide Fragments chemistry, Receptor, Notch1 chemistry
- Abstract
Intramembrane proteases typically cleave multiple substrates within their transmembrane domains (TMDs). Because substrate TMDs lack a consensus sequence around their scissile sites, it remains unclear how the enzyme discriminates substrates from nonsubstrates at the level of their TMDs. Here, we compare the previously well investigated TMDs of γ-secretase substrates C99 and Notch1 in terms of helix flexibility. Our results reveal that the low-stability site neigboring a functionally relevant diglycine hinge of C99 has an equivalent in the Notch1 TMD. This suggests that the tetra-alanine motif of Notch1 also functions as a hinge which may facilitate its cleavage.
- Published
- 2019
- Full Text
- View/download PDF
47. Modulating Hinge Flexibility in the APP Transmembrane Domain Alters γ-Secretase Cleavage.
- Author
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Götz A, Mylonas N, Högel P, Silber M, Heinel H, Menig S, Vogel A, Feyrer H, Huster D, Luy B, Langosch D, Scharnagl C, Muhle-Goll C, Kamp F, and Steiner H
- Subjects
- Amino Acid Sequence, Amyloid beta-Protein Precursor genetics, Mutation, Protein Domains, Amyloid Precursor Protein Secretases metabolism, Amyloid beta-Protein Precursor chemistry, Amyloid beta-Protein Precursor metabolism, Cell Membrane metabolism, Molecular Dynamics Simulation, Proteolysis
- Abstract
Intramembrane cleavage of the β-amyloid precursor protein C99 substrate by γ-secretase is implicated in Alzheimer's disease pathogenesis. Biophysical data have suggested that the N-terminal part of the C99 transmembrane domain (TMD) is separated from the C-terminal cleavage domain by a di-glycine hinge. Because the flexibility of this hinge might be critical for γ-secretase cleavage, we mutated one of the glycine residues, G38, to a helix-stabilizing leucine and to a helix-distorting proline. Both mutants impaired γ-secretase cleavage and also altered its cleavage specificity. Circular dichroism, NMR, and backbone amide hydrogen/deuterium exchange measurements as well as molecular dynamics simulations showed that the mutations distinctly altered the intrinsic structural and dynamical properties of the substrate TMD. Although helix destabilization and/or unfolding was not observed at the initial ε-cleavage sites of C99, subtle changes in hinge flexibility were identified that substantially affected helix bending and twisting motions in the entire TMD. These resulted in altered orientation of the distal cleavage domain relative to the N-terminal TMD part. Our data suggest that both enhancing and reducing local helix flexibility of the di-glycine hinge may decrease the occurrence of enzyme-substrate complex conformations required for normal catalysis and that hinge mobility can thus be conducive for productive substrate-enzyme interactions., (Copyright © 2019 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
48. Increased H-Bond Stability Relates to Altered ε-Cleavage Efficiency and Aβ Levels in the I45T Familial Alzheimer's Disease Mutant of APP.
- Author
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Götz A, Högel P, Silber M, Chaitoglou I, Luy B, Muhle-Goll C, Scharnagl C, and Langosch D
- Subjects
- Alzheimer Disease metabolism, Amyloid Precursor Protein Secretases metabolism, Amyloid beta-Peptides metabolism, Amyloid beta-Protein Precursor metabolism, Models, Molecular, Protein Conformation, Protein Stability, Alzheimer Disease genetics, Amyloid Precursor Protein Secretases chemistry, Amyloid beta-Peptides chemistry, Amyloid beta-Protein Precursor chemistry, Amyloid beta-Protein Precursor genetics, Hydrogen Bonding, Mutation
- Abstract
Cleavage of the amyloid precursor protein's (APP) transmembrane domain (TMD) by γ-secretase is a crucial step in the aetiology of Alzheimer's Disease (AD). Mutations in the APP TMD alter cleavage and lead to familial forms of AD (FAD). The majority of FAD mutations shift the preference of initial cleavage from ε49 to ε48, thus raising the AD-related Aβ42/Aβ40 ratio. The I45T mutation is among the few FAD mutations that do not alter ε-site preference, while it dramatically reduces the efficiency of ε-cleavage. Here, we investigate the impact of the I45T mutation on the backbone dynamics of the substrate TMD. Amide exchange experiments and molecular dynamics simulations in solvent and a lipid bilayer reveal an increased stability of amide hydrogen bonds at the ζ- and γ-cleavage sites. Stiffening of the H-bond network is caused by an additional H-bond between the T45 side chain and the TMD backbone, which alters dynamics within the cleavage domain. In particular, the increased H-bond stability inhibits an upward movement of the ε-sites in the I45T mutant. Thus, an altered presentation of ε-sites to the active site of γ-secretase as a consequence of restricted local flexibility provides a rationale for reduced ε-cleavage efficiency of the I45T mutant.
- Published
- 2019
- Full Text
- View/download PDF
49. The Metastable XBP1u Transmembrane Domain Defines Determinants for Intramembrane Proteolysis by Signal Peptide Peptidase.
- Author
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Yücel SS, Stelzer W, Lorenzoni A, Wozny M, Langosch D, and Lemberg MK
- Subjects
- Endoplasmic Reticulum metabolism, HEK293 Cells, Heme Oxygenase-1 metabolism, Humans, Mutation, Protein Domains, SEC Translocation Channels metabolism, X-Box Binding Protein 1 chemistry, X-Box Binding Protein 1 genetics, Aspartic Acid Endopeptidases metabolism, Intracellular Membranes metabolism, Proteolysis, X-Box Binding Protein 1 metabolism
- Abstract
Unspliced XBP1 mRNA encodes XBP1u, the transcriptionally inert variant of the unfolded protein response (UPR) transcription factor XBP1s. XBP1u targets its mRNA-ribosome-nascent-chain-complex to the endoplasmic reticulum (ER) to facilitate UPR activation and prevents overactivation. Yet, its membrane association is controversial. Here, we use cell-free translocation and cellular assays to define a moderately hydrophobic stretch in XBP1u that is sufficient to mediate insertion into the ER membrane. Mutagenesis of this transmembrane (TM) region reveals residues that facilitate XBP1u turnover by an ER-associated degradation route that is dependent on signal peptide peptidase (SPP). Furthermore, the impact of these mutations on TM helix dynamics was assessed by residue-specific amide exchange kinetics, evaluated by a semi-automated algorithm. Based on our results, we suggest that SPP-catalyzed intramembrane proteolysis of TM helices is not only determined by their conformational flexibility, but also by side-chain interactions near the scissile peptide bond with the enzyme's active site., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
50. Transmembrane Helix Induces Membrane Fusion through Lipid Binding and Splay.
- Author
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Scheidt HA, Kolocaj K, Veje Kristensen J, Huster D, and Langosch D
- Subjects
- Lipid Bilayers chemistry, Liposomes chemistry, Membrane Fusion, Peptides chemistry, Peptides metabolism, Phosphatidylcholines chemistry, Phosphatidylethanolamines chemistry, Phosphatidylserines chemistry, Lipid Bilayers metabolism, Liposomes metabolism
- Abstract
The fusion of biological membranes may require splayed lipids whose tails transiently visit the headgroup region of the bilayer, a scenario suggested by molecular dynamics simulations. Here, we examined the lipid splay hypothesis experimentally by relating liposome fusion and lipid splay induced by model transmembrane domains (TMDs). Our results reveal that a conformationally flexible transmembrane helix promotes outer leaflet mixing and lipid splay more strongly than a conformationally rigid one. The lipid dependence of basal as well as of TMD-driven lipid mixing and splay suggests that the cone-shaped phosphatidylethanolamine stimulates basal fusion via enhancing lipid splay and that the negatively charged phosphatidylserine inhibits fusion via electrostatic repulsion. Phosphatidylserine also strongly differentiates basal and helix-driven fusion, which is related to its preferred interaction with the conformationally more flexible transmembrane helix. Thus, the contribution of a transmembrane helix to membrane fusion appears to depend on lipid binding, which results in lipid splay.
- Published
- 2018
- Full Text
- View/download PDF
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