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Phospholipase C-gamma mediates the hydrolysis of phosphatidylinositol, but not of phosphatidylinositol 4,5-bisphoshate, in carbamylcholine-stimulated islets of langerhans.
J Biol Chem. 2001 Jun 01; 276(22):19072-7.JB

Abstract

In pancreatic islets the activation of phospholipase C (PLC) by the muscarinic receptor agonist carbamyolcholine (carbachol) results in the hydrolysis of both phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)) and phosphatidylinositol (PtdIns). Here we tested the hypothesis that PtdIns hydrolysis is mediated by PLCgamma1, which is known to be regulated by activation of tyrosine kinases and PtdIns 3-kinase. PtdIns breakdown was more sensitive than that of PtdInsP(2) to the tyrosine kinase inhibitor, genistein. Conversely, the tyrosine phosphatase inhibitor, vanadate, alone promoted PtdIns hydrolysis and acted non-additively with carbachol. Vanadate did not stimulate PtdInsP(2) breakdown. Carbachol also stimulated a rapid (maximal at 1-2 min) tyrosine phosphorylation of several islet proteins, although not of PLCgamma1 itself. Two structurally unrelated inhibitors of PtdIns 3-kinase, wortmannin and LY294002, more effectively attenuated the hyrolysis of PtdIns compared with PtdInsP(2). Adenovirally mediated overexpression of PLCgamma1 significantly increased carbachol-stimulated PtdIns hydrolysis without affecting that of PtdInsP(2). Conversely overexpression of PLCbeta1 up-regulated the PtdInsP(2), but not PtdIns, response. These results indicate that the hydrolysis of PtdIns and PtdInsP(2) are independently regulated in pancreatic islets and that PLCgamma1 selectively mediates the breakdown of PtdIns. The activation mechanism of PLCgamma involves tyrosine phosphorylation (but not of PLCgamma directly) and PtdIns 3-kinase. Our findings point to a novel bifurcation of signaling pathways downstream of muscarinic receptors and suggest that hydrolysis of PtdIns and PtdInsP(2) might serve different physiological ends.

Authors+Show Affiliations

Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney 2010, Australia.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11274217

Citation

Mitchell, C J., et al. "Phospholipase C-gamma Mediates the Hydrolysis of Phosphatidylinositol, but Not of Phosphatidylinositol 4,5-bisphoshate, in Carbamylcholine-stimulated Islets of Langerhans." The Journal of Biological Chemistry, vol. 276, no. 22, 2001, pp. 19072-7.
Mitchell CJ, Kelly MM, Blewitt M, et al. Phospholipase C-gamma mediates the hydrolysis of phosphatidylinositol, but not of phosphatidylinositol 4,5-bisphoshate, in carbamylcholine-stimulated islets of langerhans. J Biol Chem. 2001;276(22):19072-7.
Mitchell, C. J., Kelly, M. M., Blewitt, M., Wilson, J. R., & Biden, T. J. (2001). Phospholipase C-gamma mediates the hydrolysis of phosphatidylinositol, but not of phosphatidylinositol 4,5-bisphoshate, in carbamylcholine-stimulated islets of langerhans. The Journal of Biological Chemistry, 276(22), 19072-7.
Mitchell CJ, et al. Phospholipase C-gamma Mediates the Hydrolysis of Phosphatidylinositol, but Not of Phosphatidylinositol 4,5-bisphoshate, in Carbamylcholine-stimulated Islets of Langerhans. J Biol Chem. 2001 Jun 1;276(22):19072-7. PubMed PMID: 11274217.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Phospholipase C-gamma mediates the hydrolysis of phosphatidylinositol, but not of phosphatidylinositol 4,5-bisphoshate, in carbamylcholine-stimulated islets of langerhans. AU - Mitchell,C J, AU - Kelly,M M, AU - Blewitt,M, AU - Wilson,J R, AU - Biden,T J, Y1 - 2001/03/27/ PY - 2001/3/29/pubmed PY - 2001/7/28/medline PY - 2001/3/29/entrez SP - 19072 EP - 7 JF - The Journal of biological chemistry JO - J Biol Chem VL - 276 IS - 22 N2 - In pancreatic islets the activation of phospholipase C (PLC) by the muscarinic receptor agonist carbamyolcholine (carbachol) results in the hydrolysis of both phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)) and phosphatidylinositol (PtdIns). Here we tested the hypothesis that PtdIns hydrolysis is mediated by PLCgamma1, which is known to be regulated by activation of tyrosine kinases and PtdIns 3-kinase. PtdIns breakdown was more sensitive than that of PtdInsP(2) to the tyrosine kinase inhibitor, genistein. Conversely, the tyrosine phosphatase inhibitor, vanadate, alone promoted PtdIns hydrolysis and acted non-additively with carbachol. Vanadate did not stimulate PtdInsP(2) breakdown. Carbachol also stimulated a rapid (maximal at 1-2 min) tyrosine phosphorylation of several islet proteins, although not of PLCgamma1 itself. Two structurally unrelated inhibitors of PtdIns 3-kinase, wortmannin and LY294002, more effectively attenuated the hyrolysis of PtdIns compared with PtdInsP(2). Adenovirally mediated overexpression of PLCgamma1 significantly increased carbachol-stimulated PtdIns hydrolysis without affecting that of PtdInsP(2). Conversely overexpression of PLCbeta1 up-regulated the PtdInsP(2), but not PtdIns, response. These results indicate that the hydrolysis of PtdIns and PtdInsP(2) are independently regulated in pancreatic islets and that PLCgamma1 selectively mediates the breakdown of PtdIns. The activation mechanism of PLCgamma involves tyrosine phosphorylation (but not of PLCgamma directly) and PtdIns 3-kinase. Our findings point to a novel bifurcation of signaling pathways downstream of muscarinic receptors and suggest that hydrolysis of PtdIns and PtdInsP(2) might serve different physiological ends. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/11274217/Phospholipase_C_gamma_mediates_the_hydrolysis_of_phosphatidylinositol_but_not_of_phosphatidylinositol_45_bisphoshate_in_carbamylcholine_stimulated_islets_of_langerhans_ L2 - http://www.jbc.org/cgi/pmidlookup?view=long&pmid=11274217 DB - PRIME DP - Unbound Medicine ER -