Syndecan

SDCBP2 has two class II PDZ domains. PDZ domains assist protein-protein interactions by attaching to the cytoplasmic C-terminus of transmembrane proteins, and PDZ-containing proteins mediate cell signaling and the organization of protein complexes. SDCBP2 attaches to phosphatidylinositol 4, 5-bisphosphate (PIP2) and take part in nuclear PIP2 arrangement and cell division.

SDCBP is a multifunctional intracellular adapter protein. SDCBP protein has tandemly repeated PDZ domains which react with the FYA (phe-tyr-ala) carboxyterminal amino acid sequence of the syndecans. SDCBP is has a role in organization of protein complexes in the plasma membranes, regulation of B-cell development, activation of transcription factors, intracellular trafficking and cell-surface targeting, synaptic transmission, and axonal outgrowth.

Syndecan-4 is a type I integral membrane heparan sulfate proteoglycan (HSPG), which was originally isolated from cloned rat microvascular endothelial cells as an antithrombin-binding molecule, and is now known to be a member of the syndecan family. Syndecan-4 binds to basic fibroblast growth factor (bFGF), midkine, and tissue factor pathway inhibitor via its heparan sulfate chains, and is thought to be involved in various biologic functions such as signaling of bFGF, anticoagulation, and focal adhesion formation. A previous study demonstrated that syndecan-4 is expressed in various tissues, and its level of expression in the kidney is stronger than those of other syndecan family members. Thus, syndecan-4 is thought to play certain roles in maintaining renal function. Moreover, it has been reported that proteoglycans, especially sulfated proteoglycans, are involved in organogenesis of the kidney.

Syndecan 2 (SDC2) is a conserved family of heparan- and chondroitin-sulfate carrying transmembrane protein. Syndecan 2 is a cell membrane proteoglycan which modulates the activity and dynamics of some growth factor receptors and integrins. SDC2 is expressed in HSCs (hepatic stellate cells), a key cell type involved in matrix deposition in liver fibrotic disorders. SDC2 is implicated in the formation of specialized membrane domains and serves as a direct link between the extracellular environment and the organization of the cortical cytoplasm.

CD138 takes a part in cell adhesion. CD138 is expressed on the surface of pre-B cells and plasma cells but is absent from mature B cells. SDC1 is a selective marker for B cell lymphoblastic leukemia and lymphoplasmacytoid leukemia. SDC1 is missing from the apoptotic myeloma cells; therefore is a valuable marker for plasma cell and myeloma cells.