Syndecan-4 is a protein that in humans is encoded by the SDC4 gene.[5][6] Syndecan-4 is one of the four vertebrate syndecans and has a molecular weight of ~20 kDa. Syndecans are the best-characterized plasma membrane proteoglycans. Their intracellular domain of membrane-spanning core protein interacts with actin cytoskeleton and signaling molecules in the cell cortex. Syndecans are normally found on the cell surface of fibroblasts and epithelial cells. Syndecans interact with fibronectin on the cell surface, cytoskeletal and signaling proteins inside the cell to modulate the function of integrin in cell-matrix adhesion. Also, syndecans bind to FGFs and bring them to the FGF receptor on the same cell. As a co-receptor or regulator, mutated certain proteoglycans could cause severe developmental defects, like disordered distribution or inactivation of signaling molecules.
Syndecans have similar structural features:
- Attach to heparan sulfate chains – interacting factors (e.g. Matrix molecules, growth factors, and enzymes)
- Chondroitin sulfate chain
- Transmembrane domain – self-association
- C1 domain – actin-association cytoskeleton
- Variable domain – syndecan-specific
- C2 domain – attach to PDZ proteins
Syndecans normally form homodimers or multimers. Their biological function includes cell growth regulation, differentiation, and adhesion. Syndecan-4 has more widespread distribution than other syndecans and it is the only syndecan that has been found consistently in focal adhesions.[7]
- ^ a b c GRCh38: Ensembl release 89: ENSG00000124145 – Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000017009 – Ensembl, May 2017
- ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ Kojima T, Inazawa J, Takamatsu J, Rosenberg RD, Saito H (Mar 1993). "Human ryudocan core protein: molecular cloning and characterization of the cDNA, and chromosomal localization of the gene". Biochem Biophys Res Commun. 190 (3): 814–22. doi:10.1006/bbrc.1993.1122. PMID 7916598.
- ^ David G, van der Schueren B, Marynen P, Cassiman JJ, van den Berghe H (Sep 1992). "Molecular cloning of amphiglycan, a novel integral membrane heparan sulfate proteoglycan expressed by epithelial and fibroblastic cells". J Cell Biol. 118 (4): 961–9. doi:10.1083/jcb.118.4.961. PMC 2289559. PMID 1500433.
- ^ Woods A, Couchman JR (1994). "Syndecan 4 heparan sulfate proteoglycan is a selectively enriched and widespread focal adhesion component". Mol Biol Cell. 5 (2): 183–192. doi:10.1091/mbc.5.2.183. PMC 301024. PMID 8019004.