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Ly-6/uPAR or three-finger proteins (TFPs) contain a disulfide-stabilized β-structural core and three protruding loops (fingers). In mammals, TFPs have been found in epithelium and the nervous, endocrine, reproductive, and immune systems. Here, using heteronuclear NMR, we determined the three-dimensional (3D) structure and backbone dynamics of the epithelial secreted protein SLURP-1 and soluble domains of GPI-anchored TFPs from the brain (Lynx2, Lypd6, Lypd6b) acting on nicotinic acetylcholine receptors (nAChRs). Results were compared with the data about human TFPs Lynx1 and SLURP-2 and snake α-neurotoxins WTX and NTII. Two different topologies of the β-structure were revealed: one large antiparallel β-sheet in Lypd6 and Lypd6b, and two β-sheets in other proteins. α-Helical segments were found in the loops I/III of Lynx2, Lypd6, and Lypd6b. Differences in the surface distribution of charged and hydrophobic groups indicated significant differences in a mode of TFPs/nAChR interactions. TFPs showed significant conformational plasticity: the loops were highly mobile at picosecond-nanosecond timescale, while the β-structural regions demonstrated microsecond-millisecond motions. SLURP-1 had the largest plasticity and characterized by the unordered loops II/III and cis-trans isomerization of the Tyr39-Pro40 bond. In conclusion, plasticity could be an important feature of TFPs adapting their structures for optimal interaction with the different conformational states of nAChRs.

‘Three-finger’ toxin WTX from Naja kaouthia interacts with nicotinic and muscarinic acetylcholine receptors (nAChRs and mAChRs). Mutagenesis and competition experiments with 125 I-α-bungarotoxin revealed that Arg31 and Arg32 residues from the WTX loop II are important for binding to Torpedo californica and human α7 nAChRs. Computer modeling suggested that loop II occupies the orthosteric binding site at α7 nAChR. The similar toxin interface was previously described as a major determinant of allosteric interactions with mAChRs. [ABSTRACT FROM AUTHOR]

Abstract: Increased levels of differentially regulated trout protein 1 (DRTP1) mRNA transcripts have been reported in fish after activation of the acute phase response. While the function of the DRTP1 protein still remains to be elucidated, this study focused on the genomic organisation of the gene, the quantification of the DRTP1 transcript in various tissues, and the isolation and analysis of the 5′ regulatory region of the DRTP1 gene in rainbow trout (Oncorhynchus mykiss). Analysis of the DRTP1 genomic and cDNA sequences showed the gene to consist of four exons separated by three introns. Tissue localisation of the DRTP1 gene was performed by Northern analysis and validated by quantitative real-time PCR (qPCR). Six tissues (liver, intestine, spleen, brain, pituitary, and hypothalamus) were analysed. The tissues with the most abundant transcripts were the liver and the pituitary, with lesser amounts detected in the intestine, hypothalamus, brain and spleen. Genome walking allowed the isolation of a 934 bp sequence of the 5′ regulatory region of the gene which was cloned, sequenced and in which potential transcription factor binding sites were identified. Promoter fragments of decreasing size were generated and transiently transfected into the human hepatoma cell line (HepG2). Inducibility of the promoter was determined by stimulation of the HepG2 cells containing the constructs with dexamethasone, polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNFα). One construct, containing two potential C-EBP/β sites and two NF-κB sites, exhibited the highest promoter induction (6.34 fold ± SEM 0.5) when stimulated with human TNFα. A slightly shorter fragment containing one C-EBP/β site and one NF-κB site did not show any significant inducibility when treated with TNFα. The loss of the C-EBP/β and NF-κB in the shorter construct suggests that these sites, either individually or in combination, are critical for the induction of the DRTP1 promoter by TNFα. [Copyright &y& Elsevier]

Ly-6/uPAR or three-finger proteins (TFPs) contain a disulfide-stabilized β-structural core and three protruding loops (fingers). In mammals, TFPs have been found in epithelium and the nervous, endocrine, reproductive, and immune systems. Here, using heteronuclear NMR, we determined the three-dimensional (3D) structure and backbone dynamics of the epithelial secreted protein SLURP-1 and soluble domains of GPI-anchored TFPs from the brain (Lynx2, Lypd6, Lypd6b) acting on nicotinic acetylcholine receptors (nAChRs). Results were compared with the data about human TFPs Lynx1 and SLURP-2 and snake α-neurotoxins WTX and NTII. Two different topologies of the β-structure were revealed: one large antiparallel β-sheet in Lypd6 and Lypd6b, and two β-sheets in other proteins. α-Helical segments were found in the loops I/III of Lynx2, Lypd6, and Lypd6b. Differences in the surface distribution of charged and hydrophobic groups indicated significant differences in a mode of TFPs/nAChR interactions. TFPs showed significant conformational plasticity: the loops were highly mobile at picosecond-nanosecond timescale, while the β-structural regions demonstrated microsecond-millisecond motions. SLURP-1 had the largest plasticity and characterized by the unordered loops II/III and cis-trans isomerization of the Tyr39-Pro40 bond. In conclusion, plasticity could be an important feature of TFPs adapting their structures for optimal interaction with the different conformational states of nAChRs. [ABSTRACT FROM AUTHOR]