Received for publication September 21, 2005.
Revised February 17, 2006.
Accepted for publication February 17, 2006.

Dexras1 Negatively Regulates Protein Kinase C : Implications for Adenylyl Cyclase 2 Signaling

Abstract

We have identified Dexras1 as a negative regulator of protein kinase C (PKC) and the consequences of this regulation have been examined for adenylyl cyclase (EC 4.6.1.1) type 2 (AC2) signaling. Dexras1 expression in HEK293 cells completely abolished dopamine D2 receptor-mediated potentiation of AC2 activity, which is consistent with previous reports of its ability to block receptor-mediated G signaling pathways. Additionally, Dexras1 significantly reduced PMA- stimulated AC2 activity but did not alter Gs- mediated cyclic AMP accumulation. Dexras1 appeared to inhibit PMA stimulation of AC2 by interfering with PKC& [delta] autophosphorylation. This effect was selective for the isoform, as Dexras1 did not alter autophosphorylation of PKC or PKC. Dexras1 disruption of PKC autophosphorylation resulted in a significant blockade of its kinase activity as measured by [32P]-ATP incorporation using a PKC-specific substrate. Moreover, Dexras1 and PKC co-immunoprecipitated from whole cell lysates. Dexras1 did not alter the membrane translocation of PKC; however, the ability of Dexras1 to interfere with PKC autophosphorylation was isoprenylation-dependent as determined using the farnesyltransferase inhibitor, FTI- 277, and a CAAX box-deficient Dexras1 (C277S) mutant. PMA-stimulated AC2 activity was also not affected by Dexras1C277S. Collectively, these data suggest that Dexras1 functionally interacts with PKC at the cellular membrane through an isoprenylation-dependent mechanism to negatively regulate PKC activity. Moreover our study suggests that Dexras1 acts to modulate the activation of AC2 in an indirect fashion by inhibiting both G- and PKC-stimulated AC2 activity. The current study provides a novel role for Dexras1 in signal transduction.

Key words: Dopamine, Gi family, Adenylyl cyclases, Protein Kinase C, G protein regulation, Ras

This article has been cited by other articles:

				D. A. Dalmas, M. S. Scicchitano, Y. Chen, J. Kane, R. Mirabile, L. W. Schwartz, H. C. Thomas, and R. W. Boyce Transcriptional Profiling of Laser Capture Microdissected Rat Arterial Elements: Fenoldopam-induced Vascular Toxicity as a Model System Toxicol Pathol, April 1, 2008; 36(3): 496 - 519. [Abstract] [Full Text] [PDF]

				R. Newton and N. S. Holden Separating Transrepression and Transactivation: A Distressing Divorce for the Glucocorticoid Receptor? Mol. Pharmacol., October 1, 2007; 72(4): 799 - 809. [Abstract] [Full Text] [PDF]

				J. Lindsey Dexamethasone-induced Ras-related protein 1 is a potential regulatory protein in B lymphocytes Int. Immunol., May 1, 2007; 19(5): 583 - 590. [Abstract] [Full Text] [PDF]