The molecular mechanisms by which receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major signaling hubs in eukaryotes, independently relay signals across the plasma membrane have been extensively characterized. How these hubs cross-talk has been a long-standing question, but answers remain elusive. Using linear ion-trap mass spectrometry in combination with biochemical, cellular, and computational approaches, we unravel a mechanism of activation of heterotrimeric G proteins by RTKs and chart the key steps that mediate such activation. Upon growth factor stimulation, the guanine-nucleotide exchange modulator dissociates Gαi•βγ trimers, scaffolds monomeric Gαi with RTKs, and facilitates the phosphorylation on two tyrosines located within the interdomain cleft of Gαi. Phosphorylation triggers the activation of Gαi and inhibits second messengers (cAMP). Tumor-associated mutants reveal how constitutive activation of this pathway impacts cell's decision to "go" vs. "grow." These insights define a tyrosine-based G protein signaling paradigm and reveal its importance in eukaryotes.
|Number of pages||12|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Early online date||17 Nov 2020|
|Publication status||Published - 17 Nov 2020|
We thank Bridgett Simmons (AB SCIEX) for technical assistance with mass spectrometry experiments, and Yelena Pavlova and Nina Sun for technical assistance with cloning and mutagenesis of constructs. This paper was supported by the NIH Grants CA238042, AI141630, CA100768, and CA160911 (to P.G.). N.A.K. was supported by an NIH predoctoral fellowship (F31 CA206426), and T32 training Grants T32CA067754 and T32DK007202. M.G.-M. was supported by the NIH (GM136132 and GM130120). I.L.-S. was supported by a fellowship from the American Heart Association (AHA 14POST20050025). I.K. was supported by the NIH (AI118985 and R01 GM117424). T.N. is supported by National Health and Meducak Research Council C. J. Martin Early Career Fellowship 1145746.
- heterotrimeric G proteins
- growth factor receptor tyrosine kinases