Tyrphostins inhibit secretagogue-induced 1,4,5-IP3 production and amylase release in pancreatic acini

Abstract

We examined the role of protein tyrosine kinase inhibitors (tyrphostins) in secretagogue-induced inositol 1,4,5-trisphosphate (1,4,5-IP3) production and amylase secretion in rat pancreatic acinar cells. The data show that various specific cell-permeant tyrphostins (methyl 2,5-dihydroxycinnamate, tyrphostin 25, and genistein) inhibited the cholecystokinin octapeptide-, carbachol-, and bombesin-induced 1,4,5-IP3 production and amylase release. In digitonin-permeabilized cells, tyrphostins decreased 1,4,5-IP3 accumulation and amylase release generated by directly stimulating G proteins with the weakly hydrolyzable GTP analogue guanosine 5'-O-(3-thiotriphosphate). Tyrphostins had no effect on vasoactive intestinal peptide-induced amylase secretion. In isolated pancreatic acinar membranes, cholecystokinin octapeptide caused a rapid increase in tyrosine phosphorylation of a synthetic peptide containing the 12-amino acid sequence around a tyrosine phosphorylation site in pp6osrc. These results provide evidence that tyrosine kinases are involved in the activation of phospholipase C by G protein-coupled receptors in pancreatic acinar cells.

Tyrosine kinase inhibitors enhance a Ca(2+)‐activated K+ current (IAHP) and reduce IAHP suppression by a metabotropic glutamate receptor agonist in rat dentate granule neurones.

“…It is known that certain tyrosine residues in InsP3 receptors can be phosphorylated (Harnick, Jayaraman, Ma, Mulieri, Go & Marks, 1995). Thus it is possible that InsP3 action is report of tyrphostins interfering with the production of InsP3 (in pancreatic acinar cells in response to carbachol and cholecystokinin octapeptide (Piiper et al 1994)). Thus, it is possible that protein tyrosine phosphorylation influences the efficacy of mGluR-mediated activation of InsP3 production.…”

Pervanadate Stimulates Amylase Release and Protein Tyrosine Phosphorylation of Paxillin and p125FAK in Differentiated AR4-2J Pancreatic Acinar Cells

“…Effect of Pervanadate on Phospholipase C Activity-Previous reports on rat pancreatic acinar cells suggest that tyrosine kinases are involved in the activation of phospholipase C induced by different secretagogues such as cholecystokinin, bombesin, or carbachol (12,13). To test if pervanadate-stimulated amylase secretion is induced by pervanadate-mediated activation of phospholipase C, AR4-2J cells were treated with 100 M or 1 mM pervanadate for 10 s to 50 min and with 10 nM bombesin for 15 s for comparison.…”

“…It was suggested that tyrosine phosphorylation could amplify the secretory response rather than provide an obligate signal for enzyme secretion. On the other hand, tyrosine kinase inhibitors such as genistein and tyrphostin 25 were shown to inhibit agonist-induced amylase secretion and phospholipase C activation in rat pancreatic acinar cells (12,13), indicating that tyrosine kinases are involved in receptor-mediated stimulation of amylase secretion.…”

Effect of genistein on amylase release and protein tyrosine phosphorylation in parotid acinar cells

“…These results suggest that genistein inhibits amylase exocytosis through the inhibition of protein tyrosine phosphorylation. In pancreatic acini, however, genistein markedly inhibited amylase release evoked by Ca, but not by phorbol ester or cAMP [4][5][6], indicating that the inhibitory effect of genistein is strictly selective concerning secretory stimuli and cells. It is presently unknown why genistein is able to inhibit cAMPmediated amylase release in parotid acini but not in pancreatic ones.…”

“…In contrast, Ca2+-mobilizing agonists such as cholecystokinin and acetylcholine mainly stimulate amylase release from pancreatic acini, and Ca and protein kinase C seem to be equally important in the regulatory mechanism [3]. However, it was recently found that cholecystokinin and carbachol increased protein tyrosine phosphorylation in addition to serine/threonine phosphorylation and that tyrosine kinase inhibitors, including genistein, significantly inhibited amylase release stimulated by those agonists [4][5][6][7]. These results suggest that tyrosine kinases are involved in the regulation of amylase exocytosis from pancreatic acini.…”