Cooperation of G<FONT FACE= 바탕 >β and G<FONT FACE= 바탕 >αq Protein in Contractile Response of Cat Lower Esophageal Sphincter (LES)

Cooperation of G<FONT FACE= 바탕 >β and G<FONT FACE= 바탕 >αq Protein in Contractile Response of Cat Lower Esophageal Sphincter (LES)

We previously shown that LES contraction depends on M<SUB>3</SUB> receptors linked to PTX insensitive G<SUB>q</SUB> protein and activation of PLC. This results in production of IP<SUB>3</SUB>, which mediates calcium release, and contraction through a CaM dependent pathway. In the esophagus ACh activates M<SUB>2</SUB> receptors linked to PTX sensitive G<SUB>i3</SUB> protein, resulting in activation of PLD, presumably, production of DAG. We investigated the role of PLC isozymes which can be activated by Gq or G<FONT FACE= 바탕 >β protein on ACh-induced contraction in LES and esophagus. Immunoblot analysis showed the presence of 3 types of PLC isozymes, PLC-<FONT FACE= 바탕 >β1, PLC-<FONT FACE= 바탕 >β3, and PLC-<FONT FACE= 바탕 >γ1, but not PLC-<FONT FACE= 바탕 >β2, PLC-<FONT FACE= 바탕 >β4, PLC-<FONT FACE= 바탕 >γ2, PLC-<FONT FACE= 바탕 >δ1, and PLC-<FONT FACE= 바탕 >δ2 from both LES and esophageal muscle. ACh produced contraction in a dose dependent manner in LES and esophageal muscle cells obtained by enzymatic digestion with collagenase. PLC-<FONT FACE= 바탕 >β1 or PLC-<FONT FACE= 바탕 >β3 antibody incubation reduced contraction in response to ACh in LES but not in esophageal permeabilized cells, but PLC-<FONT FACE= 바탕 >γ1 antibody incubation did not have an inhibitory effect. The inhibition by PLC-<FONT FACE= 바탕 >β1 or PLC-<FONT FACE= 바탕 >β3 antibody on Ach-induced contraction was antibody concentration dependent. The combination with PLC-<FONT FACE= 바탕 >β<SUB>1</SUB> and PLC-<FONT FACE= 바탕 >β<SUB>3</SUB> antibody completely abolished the contraction, suggesting that PLC-<FONT FACE= 바탕 >β1 and PLC-<FONT FACE= 바탕 >β3 have a synergism to inhibit the contraction in LES. PLC-<FONT FACE= 바탕 >β1, -<FONT FACE= 바탕 >β3 or -<FONT FACE= 바탕 >γ1 antibody did not reduce the contraction of LES cells in response to DAG (10<SUP>&#8291;6 </SUP>M), suggesting that this isozyme of PLC may not activate PKC. When G<SUB>q/11</SUB> antibody was incubated, the inhibitory effect of the incubation of PLC <FONT FACE= 바탕 >β<SUB>3</SUB>, but not of PLC <FONT FACE= 바탕 >β<SUB>1</SUB> was additive (Fig. 6). In contrast, when G<SUB><FONT FACE= 바탕 >β</SUB> antibody was incubated, the inhibitory effect of the incubation of PLC <FONT FACE= 바탕 >β<SUB>1</SUB>, but not of PLC <FONT FACE= 바탕 >β<SUB>3</SUB> was additive. This data suggest that G<SUB>q/11</SUB> or G<FONT FACE= 바탕 >β may activate cooperatively different PLC isozyme, PLC<FONT FACE= 바탕 >β<SUB>1</SUB> or PLC<FONT FACE= 바탕 >β<SUB>3</SUB> respectively.