Regulation of adenylate cyclase by hormones and G‐proteins

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Abstract
Over the past few years, it has become apparent that a large number of transmembrane signaling systems operate through heterotrimeric G‐proteins ([1] Gilman, A.G. (1984) Cell 36, 577‐579; [2] Baker, P.F. (1986) Nature 320, 395). Adenylate cyclase is regulated by stimulatory hormones through Gs(αsβγ) and inhibitory hormones through Gi(αiβγ) ([2]; Katada, T. et al. (1984) J. Biol. Chem. 259, 3586‐3595), whereas the breakdown of phosphatidylinositol bisphosphate (PIP2) to inositol trisphosphate (IP3) and diacylglycerol (DG) by phospholipase C is probably also mediated by a heterotrimeric G‐protein (Go or Gi) [1,2]. Similarly, the activation of cGMP phosphodiesterase by light‐activated rhodopsin is mediated through the heterotrimeric G‐protein transducin (Stryer, L. (1986) Rev. Neurosci. 9, 89‐119). Other transmembrane signaling systems may also be found to involve G‐proteins similar to those already recognized. Because of the emerging universality of G‐proteins as transducers of receptor‐triggered signals, it may be useful to evaluate the current models prevailing in the adenylate cyclase field, as these models seem to guide our way in evaluating the role of G‐proteins in transmembrane signaling, in general.