RT Journal Article
SR Electronic
T1 Raf Kinase Activation of Adenylyl Cyclases: Isoform-Selective Regulation
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 921
OP 928
DO 10.1124/mol.66.4.921
VO 66
IS 4
A1 Qingming Ding
A1 Robert Gros
A1 Ian D. Gray
A1 Ronald Taussig
A1 Stephen S. G. Ferguson
A1 Ross D. Feldman
YR 2004
UL http://molpharm.aspetjournals.org/content/66/4/921.abstract
AB Adenylyl cyclases (AC), a family of enzymes that catalyze the synthesis of cyclic AMP, are critical regulators of cellular functions. The activity of adenylyl cyclase is stimulated by a range of hormone receptors, primarily via interactions with G-proteins; however, recently we identified an alternate mechanism by which growth factors sensitize adenylyl cyclase activation. We suggested that this mechanism might involve a Raf kinase-mediated serine phosphorylation of adenylyl cyclase. However, the direct involvement of a specific form of Raf kinase is yet to be demonstrated. Furthermore, whether this mechanism is generalized to other isoforms of adenylyl cyclase is unknown. In human embryonic kidney 293 cells, we now demonstrate that in reconstitution studies, c-Raf kinase can mediate phosphorylation of AC VI. Furthermore, AC VI coimmunoprecipitates with c-Raf. Raf kinase-dependent regulation of adenylyl cyclase VI is dependent on the integrity of Ser750 in the fourth intracellular loop of the enzyme and Ser603/Ser608 in the C1b region of the molecule. To examine how generalized this effect is, we studied representative isoforms of the major subfamilies of adenylyl cyclase viz., AC I, AC II, and AC V. Raf kinase-dependent sensitization/ phosphorylation of adenylyl cyclases is common to AC VI, AC V, and AC II isoforms but not AC I. In aggregate, these studies indicate that Raf kinase associates with adenylyl cyclases. Furthermore, Raf kinase regulation of adenylyl cyclase is isoform-selective. These functional interactions (as well as the physical association) between adenylyl cyclases and Raf kinases suggest an important but previously unrecognized interaction between these two key regulatory enzymes.