Thesyndecanfamilycontainsfourmembers(syndecan-1/syndecan,syndecan-2/fibroglycan,syndecan-3/N-syndecan,syndecan-4/ryudocan(amphyglycan)),whicharetransmembraneheparansulfateproteoglycans(HSPGs).TheseHSPGsexhibitcelltype-specificdistributionwithvascularendothelialcellsexpressingsyndecan-1,-2,and-4,andpredominanttargetingtobasolateralsurfaces.ThesyndecanfamilymembersaretypeIintegralmembraneproteinswithhomologoustransmembraneandcytoplasmicdomains.Thecombinedtransmembrane/cytoplasmicdomainscontainfourwell-conservedtyrosineresidues,whichmightserveimportantrolesforBIOLOGicalfunction.Thecytoplasmictailofsyndecan-4interactswithfocaladhesionmolecules.Thus,syndecan-4isknowntohavevariousbiologicalfunctionssuchasanticoagulation,celladhesionandcellmultiplication.