CD105

CD105, better known as endoglin, is a type I membrane glycoprotein that serves as an accessory receptor in the TGF-beta superfamily signaling system. Highly enriched on proliferating endothelial cells, it pairs with ALK1 and ALK5 to balance endothelial proliferation and quiescence during angiogenesis. Homozygous ENG disruption causes vascular dysplasia, and heterozygous mutations underlie hereditary hemorrhagic telangiectasia type 1, a disorder marked by recurrent nosebleeds and arteriovenous malformations. Since CD105 density reflects neovascular activity, the molecule is widely used as a marker of tumor angiogenesis and as a target for antibody-drug conjugates. The protein forms disulfide-linked homodimers on the cell surface.