Mouse CD109 Alexa Fluor® 700-conjugated Antibody

CD109 (also CPAMD7, p180, r150, Gov antigen and GPI-anchored alpha2-macroglobulin-related protein) is a 170-180 kDa member of the I39 protease inhibitor/ alpha2-macroglobulin family of thioester-containing proteins. It is expressed by endothelium, activated platelets and T cells, megakaryocyte lineage stem cells, myoepithalial cells, fibroblasts and keratinocytes. On keratinocytes, it is suggested to be a critical component of the TGF-beta receptor (T betaR) complex. Here it has been shown to specifically interact with both TGF-beta 1 and T betaRI, and generally with T betaRII and betaglycan. These interactions are inhibitory to TGF-beta signaling, likely the result of CD109's ability to promote internalization and degradation of the T betaR complex via caveolar endosomes. In human, mature CD109 is proposed to arise from a 205 kDa precursor that is cleaved intracellularly into an N-terminal 180 kDa mature molecule, and a C-terminal 25 kDa GPI-linked fragment. This occurs at an Arg tetrapeptide motif that is also conserved in mouse. On the cell surface, the 180 and 25 kDa molecules either stay "associated", or the 180 kDa mature molecule dissociates from the fragment, resulting in its solubilization. In either case, 180 kDa CD109 has the potential to be "activated" by proteolytic cleavage, generating either a 150 or 120 kDa form that may participate in covalent binding to immediately adjacent targets. Mouse CD109 is synthesized as a 1442 amino acid (aa) precursor. It contains a 21 aa signal sequence, a C-terminal prosegment (aa 1420-1442), and a 1398 aa intervening region (aa 22-1419) that possesses a potential furin processing site over aa 1271-1274. The definitive mature molecule (aa 22-1270) contains an MG2 domain (aa 129-220), a Cys thioester bond (Cys923-Gln926), and an alpha2-macroglobulin-like region (aa 961-1197). Over aa 22-1269, mouse CD109 shares 73% and 81% aa sequence identity with human and rat CD109, respectively.