Acetylcholine and cholecystokinin receptors functionally couple by different G-proteins to phospholipase C in pancreatic acinar cells |
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Authors: | S. Schnefel H. Banfic L. Eckhardt G. Schultz I. Schulz |
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Affiliation: | Max-Planck-Institut für Biophysik, Frankfurt, Main, FRG. |
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Abstract: | We have studied the involvement of GTP-binding proteins in the stimulation of phospholipase C from rat pancreatic acinar cells. Pretreatment of permeabilized cells with activated cholera toxin inhibited both cholecystokinin-octapeptide (CCK-OP) and GTPγS but not carbachol (CCh)-induced production of inositol trisphosphate. Pertussis toxin had no effect. Neither vasoactive intestinal polypeptide, a stimulator of adenylyl cyclase, nor the cAMP-analogue, 8-bromo cAMP, mimicked the inhibitory effect of cholera toxin on agonist-induced phospholipase C activation. This indicates that inhibition by cholera toxin could not be attributed to a direct interaction of cholera toxin activated Gs with phospholipase C or to an elevation of cAMP. In isolated rat pancreatic plasma membranes cholera toxin ADP-ribosylated a 40 kDa protein, which was inhibited by CCK-OP but not by CCh. We conclude from these data that both CCK- and muscarinic acetylcholine receptors functionally couple to phospholipase C by two different GTP-binding proteins. |
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Keywords: | Cholera toxin Pertussis toxin Inositol trisphosphate ADP-ribosylation GTPγS |
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