Stimulus-secretion coupling in the pancreatic acinar cell is initiated by the secretagogues CCK and ACh and results in the secretion by exocytosis of the contents of zymogen granules. A key event in this pathway is the G protein-activated production of second messengers and the subsequent elevation of cytosolic-free Ca²⁺. The aim of this study was therefore to define the heterotrimeric G protein -subunits present and participating in this pathway in rat pancreatic acinar cells. RT-PCR products were amplified from pancreatic acinar cell mRNA with primers specific for G_q, G₁₁, and G₁₄ but were not amplified with primers specific for G₁₅. The sequences of these PCR products confirmed them to be portions of the rat homologues of G_q, G₁₁, and G₁₄. The pancreatic-derived cell line AR42J similarly expressed G_q, G₁₁, and G₁₄; however, the Chinese hamster ovary (CHO) cell line only expressed G₁₁ and G_q. These data indicate that caution should be exercised when comparing signal transduction pathways between different cell types. The expression of these proteins in acinar cells was confirmed by immunoblotting samples of acinar membrane protein using specific antisera to the individual G protein -subunits. The role of these proteins in Ca²⁺ signaling events was investigated by microinjecting a neutralizing antibody directed against a homologous sequence in G_q, G₁₁, and G₁₄ into acinar cells and CHO cells. Ca²⁺ signaling was inhibited in acinar cells and receptor-bearing CHO cells in response to both physiological and supermaximal concentrations of agonists. The inhibition was >75% in both cell types. These data indicate a role for G_q and/or G₁₁ in intracellular Ca²⁺ concentration signaling in CHO cells, and in addition to G_q and G₁₁, G₁₄ may also fulfill this role in rat pancreatic acinar cells.

G_q proteins; microinjection

This article has been cited by other articles:

				M. Dufresne, C. Seva, and D. Fourmy Cholecystokinin and gastrin receptors. Physiol Rev, July 1, 2006; 86(3): 805 - 847. [Abstract] [Full Text] [PDF]

				C. Li, X. Chen, and J. A. Williams Regulation of CCK-induced amylase release by PKC-{delta} in rat pancreatic acinar cells Am J Physiol Gastrointest Liver Physiol, October 1, 2004; 287(4): G764 - G771. [Abstract] [Full Text] [PDF]

				S. L. Le Page, Y. Bi, and J. A. Williams CCK-A receptor activates RhoA through G{alpha}12/13 in NIH3T3 cells Am J Physiol Cell Physiol, November 1, 2003; 285(5): C1197 - C1206. [Abstract] [Full Text] [PDF]

				B. Ji, A. S. Kopin, and C. D. Logsdon Species Differences between Rat and Mouse CCKA Receptors Determine the Divergent Acinar Cell Response to the Cholecystokinin Analog JMV-180 J. Biol. Chem., June 16, 2000; 275(25): 19115 - 19120. [Abstract] [Full Text] [PDF]

				D. R. Giovannucci, G. E. Groblewski, J. Sneyd, and D. I. Yule Targeted Phosphorylation of Inositol 1,4,5-Trisphosphate Receptors Selectively Inhibits Localized Ca2+ Release and Shapes Oscillatory Ca2+ Signals J. Biol. Chem., October 20, 2000; 275(43): 33704 - 33711. [Abstract] [Full Text] [PDF]