Reconstitution and transphosphorylation of TGF-beta receptor complexes.
Transforming growth factor-beta (TGF-beta) signals by contacting two distantly related transmembrane serine/threonine kinases called receptors I (T beta R-I) and II (T beta R-II). TGF-beta binds to T beta R-II, which is a constitutively active kinase and this complex recruits T beta R-I, causing its phosphorylation and signal propagation to downstream substrates. The biochemical properties of this interaction were analyzed with reconstituted receptor systems. T beta R-I and T beta R-II baculovirally expressed at high levels in insect cells have the ligand binding properties of receptors expressed in mammalian cells, and form a complex in which T beta R-I phosphorylation is dependent on the kinase activity of T beta R-II. Furthermore, T beta R-I and T beta R-II can form a complex in vitro, and their cytoplasmic domains can specifically interact in a yeast two-hybrid system. In vitro complex formation with catalytically active T beta R-II is necessary and sufficient for T beta R-I phosphorylation, which within this complex does not require the catalytic activity of T beta R-I, thus mimicking T beta R-I phosphorylation in intact cells. In addition, T beta R-I phosphorylated in vitro remains associated with T beta R-II. These results suggest that T beta R-I and T beta R-II have affinity for each other, however, the ligand is required for stable complex formation under physiological conditions. Once formed, this complex is sufficient for T beta R-I phosphorylation by T beta R-II.
Ventura
F
F
Cell Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10021.
Doody
J
J
Liu
F
F
Wrana
J L
JL
Massagué
J
J
D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D018411:Spodoptera
D018125:Receptors, Transforming Growth Factor beta