Muscarinic regulation of phospholipase D and its role in arachidonic acid release in rat submandibular acinar cells
| Autor: | Norman Fleming, H. C. Chung |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Male
Phosphatidylinositol 4 5-Diphosphate medicine.medical_specialty Physiology Clinical Biochemistry Submandibular Gland In Vitro Techniques Muscarinic Agonists Rats Sprague-Dawley chemistry.chemical_compound Physiology (medical) Phosphatidylcholine Internal medicine medicine Phospholipase D Animals Phosphatidylinositol Egtazic Acid Protein kinase C Protein Kinase C Diacylglycerol kinase Chelating Agents Arachidonic Acid Phospholipase C Phosphatidic acid Receptors Muscarinic Rats Enzyme Activation Endocrinology chemistry Type C Phospholipases Phosphatidylcholines lipids (amino acids peptides and proteins) Arachidonic acid Calcium Carbachol |
| Zdroj: | Pflugers Archiv : European journal of physiology. 431(2) |
| ISSN: | 0031-6768 |
| Popis: | The characteristics of muscarinic cholinergic-induced phospholipase D (PLD) activation, and the involvement of the enzyme in the release of arachidonic acid were examined in rat submandibular acinar cells. Carbachol produced a dose-related activation of PLD to around fivefold control values at 100 microM agonist concentration. This was associated with the appearance of free choline, phosphatidic acid and arachidonic acid, indicating that the PLD substrate was phosphatidylcholine. The response to carbachol was inhibited by 60% by U73122, a blocker of a phospholipase C (PLC) specific to phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], suggesting that the cleavage of phosphatidylcholine by PLD was, at least in part, secondary to agonist-coupled hydrolysis of PtdIns(4,5)P2 by PLC. Consistent with this, PLD was also activated to levels comparable to those induced by carbachol, by the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), and the Ca2+ mobilizer, thapsigargin, two agents that respectively mimic the activation of protein kinase C (PKC) by diacylglycerol and the elevation of cytosolic Ca2+ by inositol 1,4,5-triphosphate [Ins(1,4,5)P3] in the phosphoinositide effect. The cell-permeant Ca2+ chelator 1,2-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl ester (BAPTA/AM) abolished the thapsigargin-induced activation of PLD and inhibited the responses of PLD to carbachol and TPA by 60%. The PKC inhibitor, Ro-31-8220, also inhibited the activation of PLD by carbacol and TPA to a level of approximately double control values, but had no effect on the thapsigargin-induced elevation of PLD. A role for both the PKC-associated and Ca(2+)-mobilizing arms of the PtdIns(4,5)P2-PLC pathway in PLD regulation is thus suggested. Pretreatment of cells with the phosphatidate phosphohydrolase blocker, propranolol, significantly enhanced the carbachol-induced elevation of phosphatidic acid, but decreased agonist-stimulated production of diacylglycerol and arachidonic acid, indicating that phosphatidlycholine was the likely source of arachidonic acid. We therefore propose that, in submandibular mucous acinar cells, muscarinic activation of the PtdIns(4,5)P2-PLC pathway regulates phosphatidylcholine-specific PLD through both the PKC- and Ca(2+)-mobilizing arms of the phosphoinositide response, and that diacylglycerol, derived from phosphatidylcholine via phosphatidic acid, is a source of free arachidonic acid. |
| Databáze: | OpenAIRE |
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