Unknown

Dataset Information

0

Muscarinic-agonist and guanine nucleotide activation of polyphosphoinositide phosphodiesterase in isolated islet-cell membranes.


ABSTRACT: Stimulated hydrolysis of the inositol phospholipids phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] was investigated by studying the phosphoinositides produced in a suspended preparation of plasma membranes by transference of 32P from [gamma-32P]ATP. At basal Ca2+ concentration (calculated free Ca2+, 150 nM) phospholipid hydrolysis was stimulated either by the muscarinic agonists carbamoylcholine and bethanecol or by the addition of the non-hydrolysable analogue of GTP, guanosine 5'-[beta gamma-imido]triphosphate [p(NH)ppG]. GTP was without effect on basal hyrolysis. Both GTP and p(NH)ppG enhanced the rapid (within 10 s) hydrolysis of PtdIns4P and PtdIns(4,5)P2 induced by carbamoylcholine in a dose-dependent manner. A rightward shift in the competition curve of carbamoylcholine for bound L-[3H]quinuclidinyl benzilate was seen on addition of GTP or p(NH)ppG (100 microM) under phosphorylating conditions. Pretreatment of intact islet cells with Bordetella pertussis toxin, islet-activating protein (IAP) or treatment of membranes with IAP under conditions which elicited ADP-ribosylation of a protein of Mr 41,000 was without effect on muscarinic binding, phosphoinositide phosphorylation or subsequent hydrolysis by carbamoylcholine. The findings indicate the involvement of a GTP-binding protein in the coupling of the muscarinic receptor to phosphoinositide hydrolysis in the islet cell and suggest that this is distinct from the GTP-binding regulatory component of adenylate cyclase which is covalently modified by IAP.

SUBMITTER: Dunlop ME 

PROVIDER: S-EPMC1147480 | biostudies-other | 1986 Dec

REPOSITORIES: biostudies-other

Similar Datasets

| S-EPMC1147444 | biostudies-other
| S-EPMC1163219 | biostudies-other
| S-EPMC1147575 | biostudies-other
| S-EPMC1147324 | biostudies-other
| S-EPMC1144062 | biostudies-other
| S-EPMC1148520 | biostudies-other
| S-EPMC5845781 | biostudies-literature
| S-EPMC1148619 | biostudies-other
| S-EPMC1149603 | biostudies-other
| S-EPMC1148866 | biostudies-other