Cysteine-rich domain 1 of CD40 mediates receptor self-assembly.
Ontology highlight
ABSTRACT:
SUBMITTER: Smulski CR
PROVIDER: S-EPMC3624471 | biostudies-literature | 2013 Apr
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:A critical element of lutropin bioactivity in vivo is its rapid removal from the blood by a receptor, located in hepatic endothelial cells, that recognizes the terminal sulfated carbohydrate structure SO4-4-GalNAcbeta1,4GlcNAcbeta1,2Manalpha (S4GGnM). We have previously shown that the macrophage mannose (Man)-receptor cDNA directs the synthesis of a protein that binds oligosaccharides with either terminal S4GGnM or terminal Man, at independent sites. We now show that the cysteine-rich (Cys-Rich) domain at the N terminus of the Man/S4GGnM receptor accounts for binding of oligosaccharides with terminal GalNAc-4-SO4, whereas calcium-dependent carbohydrate recognition domains (CRDs) account for binding of ligands containing terminal Man. The Cys-Rich domain is thus a previously unrecognized carbohydrate binding motif. Cys-Rich domains have been described on the three other members of the endocytic C-type lectin family of receptors. The structural relationship of these receptors to the Man/S4GGnM receptor raises the possibility that their Cys-Rich domains also bind carbohydrate moieties and contribute to their function.
| S-EPMC19259 | biostudies-literature
Project description:BackgroundInsufficient clearance of soluble oligomeric amyloid-β peptide (oAβ) in the central nervous system leads to the synaptic and memory deficits in Alzheimer's disease (AD). Previously we have identified scavenger receptor class A (SR-A) of microglia mediates oligomeric amyloid-β peptide (oAβ) internalization by siRNA approach. SR-A is a member of cysteine-rich domain (SRCR) superfamily which contains proteins actively modulating the innate immunity and host defense, however the functions of the SRCR domain remain unclear. Whether the SRCR domain of SR-AI modulates the receptor surface targeting and ligand internalization was investigated by expressing truncated SR-A variants in COS-7 cells. Surface targeting of SR-A variants was examined by live immunostaining and surface biotinylation assays. Transfected COS-7 cells were incubated with fluorescent oAβ and acetylated LDL (AcLDL) to assess their ligand-internalization capabilities.ResultGenetic ablation of SR-A attenuated the internalization of oAβ and AcLDL by microglia. Half of oAβ-containing endocytic vesicles was SR-A positive in both microglia and macrophages. Clathrin and dynamin in SR-AI-mediated oAβ internalization were involved. The SRCR domain of SR-AI is encoded by exons 10 and 11. SR-A variants with truncated exon 11 were intracellularly retained, whereas SR-A variants with further truncations into exon 10 were surface-targeted. The fusion of exon 11 to the surface-targeted SR-A variant lacking the SRCR domain resulted in the intracellular retention and the co-immunoprecipitation of Bip chaperon of the endoplasmic reticulum. Surface-targeted variants were N-glycosylated, whereas intracellularly-retained variants retained in high-mannose states. In addition to the collagenous domain, the SRCR domain is a functional binding domain for oAβ and AcLDL. Our data suggest that inefficient folding of SR-AI variants with truncated SRCR domain was recognized by the endoplasmic reticulum associated degradation which leads to the immature N- glycosylation and intracellular retention.ConclusionThe novel functions of the SRCR domain on regulating the efficacy of receptor trafficking and ligand binding may lead to possible approaches on modulating the innate immunity in Alzheimer's disease and atherosclerosis.
| S-EPMC3750411 | biostudies-literature
Project description:Wnt/β-catenin signaling is activated when extracellular Wnt ligands bind Frizzled (FZD) receptors at the cell membrane. Wnts bind FZD cysteine-rich domains (CRDs) with high affinity through a palmitoylated N-terminal "thumb" and a disulfide-stabilized C-terminal "index finger," yet how these binding events trigger receptor activation and intracellular signaling remains unclear. Here we report the crystal structure of the Frizzled-4 (FZD4) CRD in complex with palmitoleic acid, which reveals a CRD tetramer consisting of two cross-braced CRD dimers. Each dimer is stabilized by interactions of one hydrophobic palmitoleic acid tail with two CRD palmitoleoyl-binding grooves oriented end to end, suggesting that the Wnt palmitoleoyl group stimulates CRD-CRD interaction. Using bioluminescence resonance energy transfer (BRET) in live cells, we show that WNT5A stimulates dimerization of membrane-anchored FZD4 CRDs and oligomerization of full-length FZD4, which requires the integrity of CRD palmitoleoyl-binding residues. These results suggest that FZD receptors may form signalosomes in response to Wnt binding through the CRDs and that the Wnt palmitoleoyl group is important in promoting these interactions. These results complement our understanding of lipoprotein receptor-related proteins 5 and 6 (LRP5/6), Dishevelled, and Axin signalosome assembly and provide a more complete model for Wnt signalosome assembly both intracellularly and at the membrane.
| S-EPMC5458758 | biostudies-literature
Project description:Much remains to be understood about quorum-sensing factors that allow cells to sense their local density. Dictyostelium discoideum is a simple eukaryote that grows as single-celled amoebae and switches to multicellular development when food becomes limited. As the growing cells reach a high density, they begin expressing discoidin genes. The cells secrete an unknown factor, and at high cell densities the concomitant high levels of the factor induce discoidin expression. We report here the enrichment of discoidin-inducing complex (DIC), an approximately 400-kDa protein complex that induces discoidin expression during growth and development. Two proteins in the DIC preparation, DicA1 and DicB, were identified by sequencing proteolytic digests. DicA1 and DicB were expressed in Escherichia coli and tested for their ability to induce discoidin during growth and development. Recombinant DicB was unable to induce discoidin expression, while recombinant DicA1 was able to induce discoidin expression. This suggests that DicA1 is an active component of DIC and indicates that posttranslational modification is dispensable for activity. DicA1 mRNA is expressed in vegetative and developing cells. The mature secreted form of DicA1 has a molecular mass of 80 kDa and has a 24-amino-acid cysteine-rich repeat that is similar to repeats in Dictyostelium proteins, such as the extracellular matrix protein ecmB/PstA, the prespore cell-inducing factor PSI, and the cyclic AMP phosphodiesterase inhibitor PDI. Together, the data suggest that DicA1 is a component of a secreted quorum-sensing signal regulating discoidin gene expression during Dictyostelium growth and development.
| S-EPMC1151990 | biostudies-literature
Project description:Neurotrypsin (NT) is a multi-domain serine protease of the nervous system with only one known substrate: the large proteoglycan Agrin. NT has seen to be involved in the maintenance/turnover of neuromuscular junctions and in processes of synaptic plasticity in the central nervous system. Roles which have been tied to its enzymatic activity, localized in the C-terminal serine-protease (SP) domain. However the purpose of NT's remaining 3-4 scavenger receptor cysteine-rich (SRCR) domains is still unclear. We have determined the crystal structure of the third SRCR domain of murine NT (mmNT-SRCR3), immediately preceding the SP domain and performed a comparative structural analysis using homologous SRCR structures. Our data and the elevated degree of structural conservation with homologous domains highlight possible functional roles for NT SRCRs. Computational and experimental analyses suggest the identification of a putative binding region for Ca2+ ions, known to regulate NT enzymatic activity. Furthermore, sequence and structure comparisons allow to single out regions of interest that, in future studies, might be implicated in Agrin recognition/binding or in interactions with as of yet undiscovered NT partners.
| S-EPMC6423723 | biostudies-literature
Project description:The GDNF (glial cell line-derived neurotrophic factor)-binding receptor GFRalpha1 (GDNF family receptor alpha1) is attached to the membrane by a GPI (glycosylphosphatidylinositol) anchor and consists of three cysteine-rich domains. The region corresponding to the second and third domains has been shown previously to participate in ligand binding, and to interact with the transmembrane tyrosine kinase receptor RET. No function has so far been found for the N-terminal, first domain (D1). Here we show that the GPI-anchored full-length receptor binds 125I-GDNF two times more tightly than does a GPI-anchored truncated receptor lacking D1. Scintillation proximity assays with purified receptor proteins also show that the GDNF-binding capacity of the soluble full-length GFRalpha1 is two times higher than the GDNF-binding capacity of the soluble D1-truncated GFRalpha1. As RET stabilizes the binding of GDNF equally well to the full-length and truncated receptors, D1 seems not to be involved in the interaction between GFRalpha1 and RET. Moreover, soluble full-length GFRalpha1 mediates GDNF-promoted neurite outgrowth in PC6-3 cells more efficiently than the soluble truncated GFRalpha1 protein. At low concentrations, the soluble fulllength receptor mediates the phosphorylation of RET more efficiently than the soluble truncated receptor. However, when the receptors are overexpressed on the cell surface as GPI-anchored proteins, or added to the growth medium at high concentrations as soluble proteins, full-length and truncated GFRalpha1 are indistinguishable in GDNF-dependent RET-phosphorylation assays. High levels of the receptors can thus mask a slightly impaired function in the phosphorylation assay. Based on assays with both GPI-anchored and soluble receptors, we therefore conclude that D1 contributes to the optimal function of GFRalpha1 by stabilizing the interaction between GFRalpha1 and GDNF.
| S-EPMC1135013 | biostudies-literature
Project description:P2X receptors (P2XRs) are ligand-gated ion channels activated by extracellular ATP. Although the crystal structure of the zebrafish P2X4R has been solved, the exact mode of ATP binding and the conformational changes governing channel opening and desensitization remain unknown. Here, we used voltage clamp fluorometry to investigate movements in the cysteine-rich head domain of the rat P2X1R (A118-I125) that projects over the proposed ATP binding site. On substitution with cysteine residues, six of these residues (N120-I125) were specifically labeled by tetramethyl-rhodamine-maleimide and showed significant changes in the emission of the fluorescence probe on application of the agonists ATP and benzoyl-benzoyl-ATP. Mutants N120C and G123C showed fast fluorescence decreases with similar kinetics as the current increases. In contrast, mutants P121C and I125C showed slow fluorescence increases that seemed to correlate with the current decline during desensitization. Mutant E122C showed a slow fluorescence increase and fast decrease with ATP and benzoyl-benzoyl-ATP, respectively. Application of the competitive antagonist 2',3'-O-(2,4,6-trinitrophenyl)-ATP (TNP-ATP) resulted in large fluorescence changes with the N120C, E122C, and G123C mutants and minor or no changes with the other mutants. Likewise, TNP-ATP-induced changes in control mutants distant from the proposed ATP binding site were comparably small or absent. Combined with molecular modeling studies, our data confirm the proposed ATP binding site and provide evidence that ATP orients in its binding site with the ribose moiety facing the solution. We also conclude that P2XR activation and desensitization involve movements of the cysteine-rich head domain.
| S-EPMC3396496 | biostudies-literature
Project description:The class A scavenger receptor (cA-SR) family is a group of five evolutionarily related innate immune receptors. The cA-SRs are known for their promiscuous ligand binding; as they have been shown to bind bacteria, such as Streptococcus pneumoniae and Escherichia coli, as well as different modified forms of low-density lipoprotein. Three of the five family members possess a scavenger receptor cysteine-rich (SRCR) domain while the remaining two receptors lack the domain. Previous work has suggested that the macrophage-associated receptor with collagenous structure (MARCO) shares a recent common ancestor with the non-SRCR-containing receptors; however, the origin of the SRCR domain within the cA-SRs remains unknown. We hypothesize that the SRCR domains of the cA-SRs have a common origin that predates teleost fish. Using the newly available sequence data from sea lamprey and ghost shark genome projects, we have shown that MARCO shares a common ancestor with the SRCR-containing proteins. In addition, we explored the evolutionary relationships within the SRCR domain by reconstructing the ancestral SRCR domains of the cA-SRs. We identified a motif that is highly conserved between the cA-SR SRCR domains and the ancestral SRCR domain that consist of WGTVCDD. We also show that the GRAEVYY motif, a functionally important motif within MARCO, is poorly conserved in the other cA-SRs and in the reconstructed ancestral domain. Further, we identified three sites within MARCO's SRCR domain, which are under positive selection. Two of these sites lie adjacent to the conserved WGTVCDD motif, and may indicate a potential biological function for these sites. Together, these findings indicate a common origin of the SRCR domain within the cA-SRs; however, different selective pressures between the proteins may have caused MARCOs SRCR domain to evolve to contain different functional motifs when compared to the other SRCR-containing cA-SRs.
| S-EPMC4491621 | biostudies-literature
Project description:Muscle-specific kinase (MuSK) is an essential receptor tyrosine kinase for the establishment and maintenance of the neuromuscular junction (NMJ). Activation of MuSK by agrin, a neuronally derived heparan-sulfate proteoglycan, and LRP4 (low-density lipoprotein receptor-related protein-4), the agrin receptor, leads to clustering of acetylcholine receptors on the postsynaptic side of the NMJ. The ectodomain of MuSK comprises three immunoglobulin-like domains and a cysteine-rich domain (Fz-CRD) related to those in Frizzled proteins, the receptors for Wnts. Here, we report the crystal structure of the MuSK Fz-CRD at 2.1 A resolution. The structure reveals a five-disulfide-bridged domain similar to CRDs of Frizzled proteins but with a divergent C-terminal region. An asymmetric dimer present in the crystal structure implicates surface hydrophobic residues that may function in homotypic or heterotypic interactions to mediate co-clustering of MuSK, rapsyn, and acetylcholine receptors at the NMJ.
| S-EPMC2754272 | biostudies-literature
Project description:Protein S-acyltransferases (PATs) containing Asp-His-His-Cys within a Cys-rich domain (DHHC-CRD) are polytopic transmembrane proteins that are found in eukaryotic cells and mediate the S-acylation of target proteins. S-acylation is an important secondary and reversible modification that regulates the membrane association, trafficking and function of target proteins. However, little is known about the characteristics of PATs in plants. Here, we identified 804 PATs from 31 species with complete genomes. The analysis of the phylogenetic relationships suggested that all of the PATs fell into 8 groups. In addition, we analysed the phylogeny, genomic organization, chromosome localisation and expression pattern of PATs in Arabidopsis, Oryza sative, Zea mays and Glycine max. The microarray data revealed that PATs genes were expressed in different tissues and during different life stages. The preferential expression of the ZmPATs in specific tissues and the response of Zea mays to treatments with phytohormones and abiotic stress demonstrated that the PATs play roles in plant growth and development as well as in stress responses. Our data provide a useful reference for the identification and functional analysis of the members of this protein family.
| S-EPMC3796536 | biostudies-literature