Syndecans-2 and -4; close cousins, but not identical twins.
The vertebrate syndecans, which make up a four-member family of small type I transmembrane heparan sulfate proteoglycans, constitute evolutionarily conserved family proteins. In particular, sequences in the transmembrane and cytoplasmic domains are a unifying feature within the family. However, the extracellular domain sequences are molecule-specific, implying that different syndecans have evolved to carry out similar, but non-identical, functions. While all four syndecans have been implicated in regulation of the cytoskeleton, their roles are clearly complex. Recent developments indicate that the closely related syndecan-2 and -4 have separable functions, though both bind a number of ligands through their heparan sulfate chains. The specification of these activities is probably core protein related, but is it due to a distinct expression pattern or molecule-specific regulatory mechanisms? Although there is not yet enough data to provide unambiguous answers, here we shall review the known functions and regulatory mechanisms of syndecan-2 and -4.
Oh
Eok-Soo
ES
Division of Biomedical Sciences, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
Couchman
John R
JR
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D018919:Neovascularization, Physiologic; D011487:Protein Conformation; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D053669:Syndecan-2; D053671:Syndecan-4; D014018:Tissue Distribution
D006133:Growth Substances; D008562:Membrane Glycoproteins; D011509:Proteoglycans; C508245:SDC2 protein, human; C508304:SDC4 protein, human; D053671:Syndecan-4; D053669:Syndecan-2