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“This is a pre-print of an article published in journal of Cellular and Molecular Neurobiology. The final authenticated version is available online at: https://doi.org/10.1007/s10571-020-01032-9"; International audience; Rabies virus (RABV) is a neurotropic virus exclusively infecting neurons in the central nervous system. RABV encodes five proteins. Among them, the viral glycoprotein (RVG) plays a key role in viral entry into neurons and rabies pathogenesis. It was shown that the nature of the C-terminus of the RABV G protein, which possesses a PDZ-binding motif (PBM), modulates the virulence of the RABV strain. The neuronal protein partners recruited by this PBM may alter host cell function. This study was conducted to investigate the effect of RVG on synaptic function in the hippocampal dentate gyrus (DG) of rat. Two μl (108 T.U./ml) of the lentiviral vector containing RVG gene was injected into the DG of rat hippocampus. After 2 weeks, the rat’s brain was cross-sectioned and RVG-expressing cells were detected by fluorescent microscopy. Hippocampal synaptic activity of the infected rats was then examined by recording the local field potentials from DG after stimulation of the perforant pathway. Short-term synaptic plasticity was also assessed by double pulse stimulation. Expression of RVG in DG increased long-term potentiation population spikes (LTP-PS), whereas no facilitation of LTP-PS was found in neurons expressing δRVG (deleted PBM). Furthermore, RVG and δRVG strengthened paired-pulse facilitation. Heterosynaptic long-term depression (LTD) in the DG was significantly blocked in RVG-expressing group compared to the control group. This blockade was dependent to PBM motif as rats expressing δRVG in the DG-expressed LTD comparable to the RVG group. Our data demonstrate that RVG expression facilitates both short- and long-term synaptic plasticity in the DG indicating that it may involve both pre- and postsynaptic mechanisms to alter synaptic function. Further studies are needed to elucidate the underlying mechanisms.

The transcriptional co-activator with the PDZ binding motif (TAZ) is a critical regulator of numerous cellular processes such as cell differentiation, development, proliferation, and cell growth. Aberrant expression and activity of TAZ are also featured in many human malignancies. A hallmark of TAZ biology is its cytoplasmic retention mediated by 14-3-3 isoforms in response to phosphorylation of Ser

All cancer-causing human papillomavirus (HPV) E6 oncoproteins have a C-terminal PDZ-binding motif (PBM), which correlates with oncogenic potential. Nonetheless, several HPVs with little or no oncogenic potential also have an E6 PBM, with minor sequence differences affecting PDZ protein selectivity. Furthermore, certain HPV types have a phospho-acceptor site embedded within the PBM. We therefore compared HPV-18, HPV-66 and HPV-40 E6 proteins to examine the possible link between the ability to target multiple PDZ proteins and the acquisition of a phospho-acceptor site. The mutation of essential residues in HPV-18E6 reduces its phosphorylation, and fewer PDZ substrates are bound. In contrast, the generation of consensus phospho-acceptor sites in HPV-66 and HPV-40 E6 PBMs increases the PDZ proteins recognized. Thus, although phosphorylation of the E6 PBM and PDZ protein recognition are mutually exclusive, they are closely linked, with the acquisition of a phospho-acceptor site also contributing to an expansion in the number of PDZ proteins bound.

Ultraviolet (UV) irradiation induces the proliferation and differentiation of keratinocytes in the basal layer of the epidermis, which increases epidermal thickness in skin regeneration. However, the mechanism underlying this phenomenon is not yet known in detail. In this study, we aimed to demonstrate that the transcriptional coactivator with PDZ-binding motif (TAZ) stimulates epidermal regeneration by increasing keratinocyte proliferation. During epidermal regeneration, TAZ is localized in the nucleus of keratinocytes of the basal layer and stimulates epidermal growth factor receptor (EGFR) signaling. TAZ depletion in keratinocytes decreased EGFR signaling activation, which delays epidermal regeneration. Interestingly, TAZ stimulated the transcription of amphiregulin (AREG), a ligand of EGFR, through TEAD-mediated transcriptional activation. Together, these results show that TAZ stimulates EGFR signaling through AREG induction, suggesting that it plays an important role in epidermal regeneration.

Influenza A viruses (IAVs) have multiple mechanisms for altering the host immune response to aid in virus survival and propagation. While both type I and II interferons (IFNs) have been associated with increased bacterial superinfection (BSI) susceptibility, we found that in some cases type I IFNs can be beneficial for BSI outcome. Specifically, we have shown that antagonism of the type I IFN response during infection by some IAVs can lead to the development of deadly BSI. The nonstructural protein 1 (NS1) from IAV is well known for manipulating host type I IFN responses, but the viral proteins mediating BSI severity remain unknown. In this study, we demonstrate that the PDZ-binding motif (PDZ-bm) of the NS1 C-terminal region from mouse-adapted A/Puerto Rico/8/34-H1N1 (PR8) IAV dictates BSI susceptibility through regulation of IFN-α/β production. Deletion of the NS1 PDZ-bm from PR8 IAV (PR8-TRUNC) resulted in 100% survival and decreased bacterial burden in superinfected mice compared with 0% survival in mice superinfected after PR8 infection. This reduction in BSI susceptibility after infection with PR8-TRUNC was due to the presence of IFN-β, as protection from BSI was lost in Ifn-β(−/−) mice, resembling BSI during PR8 infection. PDZ-bm in PR8-infected mice inhibited the production of IFN-β posttranscriptionally, and both delayed and reduced expression of the tunable interferon-stimulated genes. Finally, a similar lack of BSI susceptibility, due to the presence of IFN-β on day 7 post-IAV infection, was also observed after infection of mice with A/TX98-H3N2 virus that naturally lacks a PDZ-bm in NS1, indicating that this mechanism of BSI regulation by NS1 PDZ-bm may not be restricted to PR8 IAV. These results demonstrate that the NS1 C-terminal PDZ-bm, like the one present in PR8 IAV, is involved in controlling susceptibility to BSI through the regulation of IFN-β, providing new mechanisms for NS1-mediated manipulation of host immunity and BSI severity.

Scribble (SCRIB) is an important adaptor protein that controls the establishment and maintenance of apico-basal cell polarity. To better understand how SCRIB controls cell polarity signalling via its PDZ domains, we investigated human SCRIB interactions with adenomatous polyposis coli (APC). We show that SCRIB PDZ1, PDZ2 and PDZ3 are the major interactors with the APC PDZ-binding motif (PBM), whereas SCRIB PDZ4 does not show detectable binding to APC. We then determined the crystal structure of SCRIB PDZ1 domain bound to the APC PBM. Our findings reveal a previously unreported pattern of interactions between the SCRIB PDZ domain region with the C-terminal PDZ binding motif of APC, where SCRIB PDZ1 domain is the highest affinity site.

“This is a pre-print of an article published in J. Neurovirol. The final authenticated version is available online at: https://doi.org/10.1007/s13365-021-00972-2”; International audience; Rabies is a life-threatening viral infection of the brain. Rabies virus (RABV) merely infects excitable cells including neurons provoking drastic behaviors including negative emotional memories. RABV glycoprotein (RVG) plays a critical role in RABV pathogenesis. RVG interacts with various cytoplasmic PDZ (PSD-95/Dlg/ZO-1) containing proteins through its PDZ binding motif (PBM). PTZ domains have crucial role in formation and function of signal transduction. Hippocampus is one of the cerebral regions that contains high load of viral antigens. We examined impact of RVG expression in the dorsal hippocampus on aversive as well as spatial learning and memory performance in rats. Two μl of the lentiviral vector (~108 T.U. /ml) encoding RVG or ∆RVG (deleted PBM) genomes was microinjected into the hippocampal CA1. After one week, rat’s brain was cross-sectioned and RVG/∆RVG-expressing neuronal cells were confirmed by fluorescent microscopy. Passive avoidance and spatial learning and memory were assessed in rats by Shuttle box and Morris water maze (MWM). In the shuttle box, both RVG and ∆RVG decreased the time spent in the dark compartment compared to control (p

Postsynaptic density-95, disks-large, and zonula occludens-1 (PDZ) domain interactions with cognate linear binding motifs (i.e., PDZ-binding motifs or PBMs) are important for many biological processes and can be pathological when disrupted. There are hundreds of PDZ–PBM interactions reported but few have been quantitatively determined. Moreover, PDZ–PBM interactions have been identified as potential therapeutic targets. To thoroughly understand PDZ–PBM binding energetics and their specificity, we have developed a sensitive and quantitative equilibrium binding assay. Here, we describe a protocol for determining PDZ–PBM binding energetics using fluorescence anisotropy-based methodology.

Background Hepatic fibrosis is a complex and dynamic process similar to “wound healing” that results in the progressive accumulation of connective tissue. We aimed to investigate the epigenetic control of liver fibrosis and Hippo pathway in human hepatic stellate cell (HSC) line. We examined the effect of Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor on the LX2 cell line. Material and methods 2.5 μM SAHA was treated to LX2 cell line for 2 days. Cell proliferation and apoptosis measurement were performed by Muse Cell Analyzer. Yes-Associated Protein/Transcrıptional Coactivator With Pdz-Binding Motif (YAP/TAZ) and alpha-smooth muscle actin (α-SMA) protein expression levels were measured by western blotting. Results In our study, we observed that the SAHA treatment reduced cell viability and induced apoptosis of LX2 cells statistically. We found that SAHA treatment decreased α-SMA, YAP and TAZ proteins levels statistically. Conclusion Decreased cell viability could be due to physiological, autophagical and also related to the apoptotical mechanisms. We thought that SAHA plays an important role in the creation of the fates of the LX2 cell line.

The original version of this article unfortunately contained two mistakes.

International audience; PDZ domains recognize PDZ Binding Motifs (PBMs) at the extreme C-terminus of their partner proteins. The human proteome contains 266 identified PDZ domains, the PDZome, spread over 152 proteins. We previously developed the "holdup" chromatographic assay for high-throughput determination of PDZ-PBM affinities. In that work, we had used an expression library of 241 PDZ constructs (the "PDZome V.1"). Here, we cloned, produced, and characterized a new bacterial expression library ("PDZome V.2"), which comprises all the 266 known human PDZ domains as well as 37 PDZ tandem constructs. To ensure the best expression level, folding, and solubility, all construct boundaries were redesigned using available structural data and all DNA sequences were optimized for Escherichia coli expression. Consequently, all the PDZ constructs are produced in a soluble form. Precise quantification and quality control were carried out. The binding profiles previously published using "PDZome V.1" were reproduced and completed using the novel "PDZome V.2" library. We provide here the detailed description of the high-throughput protocols followed through the PDZ gene synthesis and cloning, PDZ production, holdup assay and data treatment.

Background A splice product of the E6 oncoprotein, E6*, is found in cells infected with HPV associated with a high-risk for cervical cancer. Both E6* and E6 promote Dlg degradation, considered a contributing factor for the tumorigenic potential of high-risk HPVs. The full-length E6 utilizes a conserved PDZ binding motif (PBM) at the extreme C-terminus to promote Dlg degradation. In contrast, this PBM is absent in E6*. Methods We performed western blot analysis, site-directed mutagenesis and co-immunoprecipitation to identify the key elements required for Dlg degradation activity of high-risk HPVE6*, using HPV16E6* as a model. Results Our data indicate that only one of the two internal putative class III PBMs, located between amino acids 24–27 (HDII) of HPV16E6*, was required to facilitate degradation of Dlg protein. Substitution of the two consensus residues in this region (D25 and I27) to glycine greatly diminished activity. Whereas substitution of the two conserved residues in the putative internal class I PBM (amino acids 16–19) or the second putative class III PBM (amino acids 28–31) was without effect. Interestingly, HPV66E6* which does not promote Dlg degradation can be converted into a form capable of facilitating Dlg degradation through the insertion of nine amino acids (20–28) containing the class III PBM from HPV16E6*. HPV16E6*-induced Dlg degradation appeared independent of E6AP. Conclusions The internal class III PBM of HPV16E6*I required for Dlg degradation is identified. General significance This study highlights that a novel class III PBM as the domain responsible for Dlg degradation activity in high-risk HPVE6*.

The OC43 strain of human coronavirus (HCoV-OC43) is an ubiquitous respiratory tract pathogen possessing neurotropic capacities. Coronavirus structural envelope (E) protein possesses specific motifs involved in protein-protein interaction or in homo-oligomeric ion channel formation, which are known to play various roles including in virion morphology/assembly and in cell response to infection and/or virulence. Making use of recombinant viruses either devoid of the E protein or harboring mutations either in putative transmembrane domain or PDZ-binding motif, we demonstrated that a fully functional HCoV-OC43 E protein is first needed for optimal production of recombinant infectious viruses. Furthermore, HCoV-OC43 infection of human epithelial and neuronal cell lines, of mixed murine primary cultures from the central nervous system and of mouse central nervous system showed that the E protein is critical for efficient and optimal virus replication and propagation, and thereby for neurovirulence., Highlights • Coronavirus structural envelope (E) protein specific motifs involved in protein-protein interaction or in homo-oligomeric ion channel formation are needed for optimal production of recombinant infectious virus. • Fully functional E protein of HCoV-OC43 is crucial for viral propagation in the CNS and neurovirulence. • Fully functional E protein of HCoV-OC43 is crucial for efficient viral propagation in the central nervous system and thereby for neurovirulence.

The topographical environment, which mimics the stem cell niche, provides mechanical cues to regulate the differentiation of mesenchymal stem cells (MSC). Diverse topographical variations have been engineered to investigate cellular responses; however, the types of mechanical parameters that affect cells, and their underlying mechanisms remain largely unknown. In this study, we screened nanotopological pillars with size gradient to activate transcriptional coactivator with PDZ binding motif (TAZ), which stimulates osteogenesis of MSC. We observed that a nanotopological plate, 70 nm in diameter, significantly induces osteogenic differentiation with the activation of TAZ. TAZ activation via the nanotopological plate was mediated by actin polymerization and Rho signaling, as evidenced by the cytosolic localization of TAZ under F-actin or Rho kinase inhibitor. The FAK and MAPK pathways also play a role in TAZ activation by the nanotopological plate because the inhibitor of ERK and JNK blocked nanopattern plate induced osteogenic differentiation. Taken together, these results indicate that nanotopology regulates cell differentiation through TAZ activation.

Human T-lymphotropic viruses type 1 (HTLV-1) and type 2 (HTLV-2) present very similar genomic structures but HTLV-1 is more pathogenic than HTLV-2. Is this difference due to their transactivating Tax proteins, Tax-1 and Tax-2, which are responsible for viral and cellular gene activation? Do Tax-1 and Tax-2 differ in their cellular localization and in their interaction pattern with cellular factors? In this review, we summarize Tax-1 and Tax-2 structural and phenotypic properties, their interaction with factors involved in signal transduction and their localization-related behavior within the cell. Special attention will be given to the distinctions between Tax-1 and Tax-2 that likely play an important role in their transactivation activity.

Effective and safe induction of osteogenic differentiation is one of the key elements of bone tissue engineering. Surface topography of scaffold materials was recently found to promote osteogenic differentiation. Utilization of this topography may be a safer approach than traditional induction by growth factors or chemicals. The aim of this study is to investigate the enhancement of osteogenic differentiation by surface topography and its mechanism of action. Hydroxyapatite (HA) discs with average roughness (Ra) of surface topography ranging from 0.2 to 1.65 μm and mean distance between peaks (RSm) ranging from 89.7 to 18.6 μm were prepared, and human bone-marrow mesenchymal stem cells (hBMSCs) were cultured on these discs. Optimal osteogenic differentiation was observed on discs with surface topography characterized by Ra ranging from 0.77 to 1.09 μm and RSm ranging from 53.9 to 39.3 μm. On this surface configuration of HA, hBMSCs showed oriented attachment, F-actin arrangement, and a peak in the expression of Yes-associated protein (YAP) and PDZ binding motif (TAZ) (YAP/TAZ). These results indicated that the surface topography of HA promoted osteogenic differentiation of hBMSCs, possibly by increasing cell attachment and promoting the YAP/TAZ signaling pathway.

Cancer-causing HPV E6 oncoproteins are characterized by the presence of a PDZ binding motif (PBM) at their extreme carboxy terminus. It was long thought that this region of E6 had a sole function to confer interaction with a defined set of cellular substrates. However, more recent studies have shown that the E6 PBM has a complex pattern of regulation, whereby phosphorylation within the PBM can regulate interaction with two classes of cellular proteins: those containing PDZ domains and the members of the 14-3-3 family of proteins. In this review, we explore the roles that the PBM and its ligands play in the virus life cycle, and subsequently how these can inadvertently contribute towards the development of malignancy. We also explore how subtle alterations in cellular signal transduction pathways might result in aberrant E6 phosphorylation, which in turn might contribute towards disease progression.

Kir5.1, a nonfunctional inwardly rectifying K+ channel by itself, can form functional channels by assembling with other proteins. We previously showed that Kir5.1 assembled with Kir4.1 and functioned as an acid-base regulator in the kidney. In this study, we examined the intrarenal distribution of Kir5.1 by RT-PCR analysis on dissected nephron segments and immunohistochemical analysis with the specific anti-Kir5.1 antibody. Strong expression of Kir5.1 was detected in distal convoluted tubules, and weak expression was also detected in thick ascending limb of Henle's loop. Colocalization of Kir5.1 with Kir4.1 indicated expression of Kir5.1/Kir4.1 heteromer in these nephron segments. In a renal epithelial cell line, Madin-Darby canine kidney cells, heteromer formation with Kir4.1 changed the localization of Kir5.1 from intracellular components to the cell surface. The COOH-terminal cytoplasmic portion that includes the PDZ binding motif of Kir4.1 was responsible for this intracellular localization. These data suggest the signals on the COOH terminus of Kir4.1, including PDZ binding motif, determine the intracellular localization of Kir5.1/Kir4.1 heteromer in distal tubules.

High-risk human papillomavirus (HPV) E6 proteins have a C-terminal PDZ binding motif through which they bind, and target for proteasome-mediated degradation, a number of PDZ-containing cellular targets. Recent studies have suggested that the RING-containing ubiquitin-protein ligase PDZRN3 might also be an HPV E6 target. In this analysis, we show that HPV-16 and HPV-18 E6 can target PDZRN3 in a PDZ- and proteasome-dependent manner and provide a connection between the HPV life cycle and differentiation-related STAT signaling.

Down syndrome-associated acute megakaryoblastic leukemia (DS-AMKL) affects 1 in 500 children with DS and associates uniformly with somatic mutations in GATA1. DS-AMKL is often treated successfully; however, treatments can cause long-term side effects, such that mechanistic insights and targeted therapies are needed. Recent studies report a recurring L340F mutation in DCAF7 in DS-AMKL, at the C-terminus of the protein. A highly conserved scaffold protein, DCAF7 is a cofactor for the chromosome 21-encoded kinase, DYRK1A, and shares 100% protein sequence homology among vertebrates. In our efforts to characterize the normal function of DCAF7 in hematopoiesis and its contribution to AMKL, we have identified an unreported PDZ-binding motif (PBM) in DCAF7, which is perturbed by the L340F mutation. Overexpression of mutant (DCAF7mut), but not wild type DCAF7 (DCAF7wt), in a mouse model of DS with a Gata1 mutation leads to rapid onset of dysplastic disease characterized by peripheral blood leukopenia and thrombocytopenia, with normal red cell numbers. Bone marrow of affected mice harbors abnormal, hyperproliferative erythroid progenitors and diminished, hyperchromatic megakaryocytes, with stark depletion of granulocytic and lymphoid lineages and widespread edema. Splenic architecture is grossly abnormal, with a complete absence of white pulp, proliferation of erythroid precursors, and significant numbers of apoptotic, hyperchromatic megakaryocytes. Conversely, targeted deletion of Dcaf7 in hematopoiesis shifts the myeloid-erythroid balance toward the myeloid lineage, with increased granulopoiesis and hyperchromatic megakaryocytes in the bone marrow and lower white blood cell numbers and dramatic thrombocytopenia in the peripheral blood. Splenic architecture is largely normal, although flow cytometry reveals defective B- and T- cell development. The bone marrow knockout phenotype of Dcaf7 is strongly reminiscent of the cellular phase of primary myelofibrosis (PMF). Combined with bone marrow overexpression phenotypes, which resemble hemophagocytic syndrome, our data suggest that DCAF7 is critically important for maintaining a healthy bone marrow environment and regulating blood cell lineage choice. In order to identify functional binding partners of the DCAF7 PDZ-binding motif (PBM) that may support these functions, we performed IP mass spectrometry using DCAF7wt or DCAF7mut as bait and found two highly conserved PDZ-domain containing scaffold proteins, PAR3 and PDLIM5, that interact robustly with DCAF7wt, but not with DCAF7mut. While both DCAF7wt and DCAF7mut are able to associate with DYRK1A, the ability of DCAF7 to bring DYRK1A activity to the PAR3 and PDLIM5 signaling hubs affects the composition of DCAF7-scaffolded transcriptional complexes and downstream transcriptional outcomes. Through RNA-sequencing and Ingenuity Pathways Analysis, overexpression of both DCAF7wt and DCAF7mut in mouse bone marrow leads to the induction of interferon response genes; however, DCAF7wt also induces a pro-apoptotic gene program, whereas DCAF7mut instead promotes survival gene expression and developmental reprogramming. Consistently, expression of DCAF7wt in bone marrow progenitors causes rapid expansion and increased initial colony forming ability, but decreased replating potential compared with vector control. Conversely, expression of DCAF7mut causes increased proliferation and colony formation accompanied by enhanced replating, indicating greater self-renewal conferred by DCAF7mu. Our data indicate DCAF7 regulates the balance of proliferation, differentiation and apoptosis in hematopoietic cells and that the PBD of DCAF7 is critically important for these functions, connecting DCAF7 to signaling hubs that translate environmental cues into appropriate transcriptional outcomes. Furthermore, DCAF7 disruption causes hematopoietic disease reminiscent of human pathology, suggesting it may have broad significance in hematopoietic malignancy. Finally, our data support a model wherein DCAF7 mutation facilitates the development of malignancy by promoting the survival and proliferation of mutant clones in the bone marrow and fundamentally altering the bone marrow microenvironment. Disclosures No relevant conflicts of interest to declare.