Antibody detects endogenous levels of TGFBR1 only when phosphorylated at Thr204. TGFBR1 is a transmembrane serine/threonine kinase in the TGFBR1 superfamily, which also includes ACVRs and BMPRs. Upon binding TGF-b, TGFBR2 dimerizes with and activates TGF