The protein complex of dimeric TGF-beta-1 with the type II receptor dimer (dimeric TGFB1:TGFBR2 homodimer) recruits the low affinity receptor, type I receptor (TGFBR1), thus forming a hetero-tetrameric receptor bound to the dimeric ligand on the extracellular face of the plasma membrane (TGFB1:TGFBR2:TGFBR1) (Wrana et al. 1992, Moustakas et al. 1993, Franzen et al. 1993). FKBP1A (FKBP12), a peptidyl-prolyl cis-trans isomerase, forms a complex with TGFBR1 and prevents phosphorylation of TGFBR1 by TGFBR2 in the absence of ligand. FKBP1A dissociates from TGFBR1 after it forms a complex with ligand-activated TGFBR2 (Chen et al. 1997). TGFBR1 can homodimerize in the absence of TGFB1 when overexpressed, but under physiological conditions it exists as a monomer on the surface of unstimulated cells. TGFB1-induced dimerization of TGFBR1 is TGFBR2-dependent (Zhang et al. 2010).
Xu, L, Yuan, J, Chen, YG, Wang, Q, Zuo, W, Zhang, W, Fang, X, Yang, Y
Miyazono, K, Schulz, P, Yamashita, H, Ichijo, H, ten Dijke, P, Heldin, CH, Franzen, P
O'Connor-McCourt, MD, Lodish, HF, Plamondon, J, Henis, YI, Moustakas, A, Lin, HY
Massague, J, Liu, F, Chen, YG
Massague, J, Wrana, JL, Carcamo, J, Laiho, M, Attisano, L, Doody, J, Wang, XF, Zentella, A
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