CD109 molecule (CD109)

CD109 molecule is a **glycosylphosphatidylinositol (GPI)-anchored glycoprotein** expressed on the surface of platelets, activated T cells, endothelial cells, and various epithelial cells[2][4]. It is a member of the **alpha-2-macroglobulin/complement (C3, C4, C5) protein family** and acts as both a **protease inhibitor** and a core regulatory molecule for **TGF-beta (transforming growth factor-beta) signaling**[1][2][3][4]. CD109 inhibits TGF-beta signaling by binding the ligand and regulating the fate of TGF-beta receptors, promoting their caveolar internalization and degradation. Upon cleavage by proteases, it exposes a reactive thioester group to trap and neutralize proteases, thereby participating directly in the control of proteolytic activity[1][3]. CD109 is involved in the regulation of **inflammatory responses, epithelial–mesenchymal transition, cell proliferation, wound healing, and fibrosis**[2][4][5]. Its expression is altered in several cancers, especially **squamous cell carcinoma**, where it helps maintain epithelial characteristics and suppresses transitions to more aggressive phenotypes[5]. CD109 serves as a multifunctional regulatory protein, impacting both immune and non-immune cellular processes.

Other names

CD109 antigenCPAMD7150 kDa TGF-beta-1-binding proteinC3 and PZP-like alpha-2-macroglobulin domain-containing protein 7Platelet-specific Gov antigenp180r150Gov platelet alloantigensactivated T-cell marker CD109

Negative regulation of TGF-beta by acting as a co-receptor and promoting internalization/degradation of TGF-beta receptors; Protease trapping and inhibition via thioester bond formation upon protease cleavage; Modulation of NF-kB and cytokine signaling