|Detection of Syndecan-2/CD362 in Human Blood Monocytes by Flow Cytometry. Human peripheral blood monocytes were stained with Mouse Anti-Human CD14 APC‑conjugated Monoclonal Antibody (Catalog # FAB3832A) and either (A) Rat Anti-Human Syndecan-2/CD362 PE‑conjugated Monoclonal Antibody (Catalog # FAB2965P) or (B) Rat IgG2B Phycoerythrin Isotype Control (Catalog # IC013P). View our protocol for Staining Membrane-associated Proteins.|
Syndecan-2, previously known as fibroglycan or heparan sulfate proteoglycan, is a member of the syndecan family of Type 1 transmembrane proteins capable of carrying heparan sulfate (HS) and chondroitin sulfate glycosaminoglycans. The four vertebrate syndecans show conserved cytoplasmic domains and divergent extracellular portions (except for GAG attachment sites). Among the Syndecans, Syndecan-2 is most similar to Syndecan-4 (1‑3). Human Syndecan-2 is synthesized as a 201 amino acid (aa) core protein with an 18 aa signal sequence, a 126 aa extracellular domain (ECD), a 25 aa transmembrane region and a 32 aa cytoplasmic tail (4). The human ECD of Syndecan-2 contains three closely-spaced consensus Ser-Gly sequences for the attachment of HS side chains. It shares 76%, 73%, 87%, 78% and 63% aa identity with the ECD of mouse, rat, bovine, canine and chicken Syndecan-2, respectively. The cytoplasmic tail has both serine and tyrosine phosphorylation sites. Addition of 20‑80 disaccharides per side chain adds considerably to the size of the 22 kDa core protein. Non-covalent homodimerization of Syndecan-2 is dependent on the transmembrane domain (5). Syndecan-2 is expressed in cells of mesenchymal origin, neuronal and epithelial cells, and is the predominant syndecan expressed during embryonic development. Expression is upregulated in several cancer cell lines (6). After induction in macrophages by inflammatory mediators, Syndecan-2 selectively binds FGFbasic, VEGF and EGF (7). Syndecan-2 expressed on human primary osteoblasts binds GM-CSF and may function as a co‑receptor (8). Activated endothelial cell Syndecan-2 specifically binds IL-8 and may participate in promoting neutrophil extravasation by forming a chemotactic IL-8 gradient (9). Typically, cytokine, chemokine and extracellular matrix protein binding occurs through interaction with HS side chains, but the Syndecan-2 extracellular domain can bind TGF-beta directly via protein-protein interaction (10).