Human betaIG-H3 Antibody

Beta IG-H3, also known as TGFBI and RGD-CAP, is a matricellular adaptor protein that is induced in most cell types in response to TGF-beta stimulation (1-4). The human betaIG-H3 cDNA encodes a 683 amino acid (aa) precursor that includes a 23 aa signal sequence, one EMI domain, four FAS1 domains, and one RGD motif (1). Human betaIG-H3 shares 91% and 93% aa sequence identity with mouse and porcine betaIG-H3, respectively. betaIG-H3 is expressed as a 75 kDa protein with no post-translational additions (5). Following secretion, cleavages at multiple positions near the C-terminal end liberate peptides with pro-apoptotic activity (5,6). Peptides that encompass the RGD motif contribute to the pro-apoptotic effects of TGF-beta (6). FAS1 domains contain YH motifs that are characterized by conserved Tyr and His residues (7). The YH motifs in each of the FAS1 domains enable betaIG-H3 binding to matrix Fibronectin, Collagen I, and Collagen VI (3, 8 - 10) in addition to cell expressed Integrins alpha_V beta₃, alpha_V beta₅, and alpha₃ beta₁ (7, 8, 11, 12). The expression of betaIG-H3 is modulated at particular developmental stages in some cell types. It is upregulated in keratinocytes and immature dendritic cells but downregulated in osteoblasts (8, 11, 13). It promotes keratinocyte differentiation but blocks osteoblast differentiation (8,11). betaIG-H3 stimulates macrophage endocytosis and vascular endothelial cell proliferation and migration (12, 13). High glucose levels induce betaIG-H3 in renal proximal tubule cells which is predictive of diabetic nephropathy (3). Several point mutations (clustered in the fourth FAS1 domain) of betaIG-H3 are linked to different corneal dystrophies (14). betaIG-H3 is downregulated in many cancers (4, 15) and functions as a suppressor of tumorigenicity when overexpressed (2, 4, 15).