The incorporation of 32P into the nucleotides of ribonucleic acid in pigeon pancreas slices

“…4 is a general one. Hokin and Hokin (23) observed that the pancreas responds to cholinergic agents with an increased turnover in PtdIns. As reviewed recently (1), this phenomenon is found in nervous tissue, pancreas, salivary glands, thyroid, lymphocytes, smooth muscle, and platelets.…”

Section: Resultsmentioning

confidence: 99%

Diglyceride lipase: a pathway for arachidonate release from human platelets.

Bell¹,

Kennerly²,

Stanford³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

610

217

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We provide evidence that the mechanism for arachidonate release from stimulated human platelets involves two enzymes: a phosphatidylinositol-specific phospholipase C (EC 3.1.4.10) and a diglyceride lipase. After incubation of platelets with thrombin for 15 seconds, 1.2 nmol of 1-stearoyl-2-arachidonoyl diglyceride per 109 platelets was isolated. Arachidonate was released from this substrate by the action of diglyceride lipase located in the particulate fraction of platelets. The enzyme has a pH optimum of 7.0, is stimulated by calcium ions and reduced gutathione, and liberates 31 nmol of fatty acid per min per Ignofplatelet particulate protein. The diglyceride lipase has sufficient activity to account for the 5-10 nmol of arachidonate released per 109 platelets upon thrombin stimulation. That only arachidonate is released upon thrombin stimulation may be explained by the fact that the diglyceride substrate in platelets contains only arachidonate in the 2 position. The lipase activity found in platelet membranes can also hydrolyze the 1-position fhtty acid. Stearate is not released when intact platelets are stimulated with thrombin, and the fate of this fatty acid remains to be elucidated. Several tissues, including blood platelets, exhibit the so-called "inositol effect" when stimulated by appropriate agonists (1

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“…The importance of inositol phospholipids, especially the polyphosphoinositides, in cell function was first recognized because of their involvement in cell signaling as substrates for phospholipase C with the resulting production of Ins(1,4,5)P 3 1 and diacylglycerol (1)(2)(3). It was subsequently found that the PtdIns-4,5-P 2 could directly interact with and regulate the function of several cytoskeletal proteins (4 -7), indicating the lipids are likely to be able to regulate other complex cellular functions.…”

mentioning

confidence: 99%

A Pleckstrin Homology Domain Specific for Phosphatidylinositol 4,5-Bisphosphate (PtdIns-4,5-P2) and Fused to Green Fluorescent Protein Identifies Plasma Membrane PtdIns-4,5-P2 as Being Important in Exocytosis

Holz¹,

Hlubek²,

Sorensen³

et al. 2000

Journal of Biological Chemistry

181

161

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Kinetically distinct steps can be distinguished in the secretory response from neuroendocrine cells with slow ATP-dependent priming steps preceding the triggering of exocytosis by Ca 2؉ . One of these priming steps involves the maintenance of phosphatidylinositol 4,5-bisphosphate (PtdIns-4,5-P 2 ) through lipid kinases and is responsible for at least 70% of the ATP-dependent secretion observed in digitonin-permeabilized chromaffin cells. PtdIns-4,5-P 2 is usually thought to reside on the plasma membrane. However, because phosphatidylinositol 4-kinase is an integral chromaffin granule membrane protein, PtdIns-4,5-P 2 important in exocytosis may reside on the chromaffin granule membrane. In the present study we have investigated the localization of PtdIns-4,5-P 2 that is involved in exocytosis by transiently expressing in chromaffin cells a pleckstrin homology (PH) domain that specifically binds PtdIns-4,5-P 2 and is fused to green fluorescent protein (GFP). The PH-GFP protein predominantly associated with the plasma membrane in chromaffin cells without any detectable association with chromaffin granules. Rhodamine-neomycin, which also binds to PtdIns-4,5-P 2 , showed a similar subcellular localization. The transiently expressed PH-GFP inhibited exocytosis as measured by both biochemical and electrophysiological techniques. The results indicate that the inhibition was at a step after Ca 2؉ entry and suggest that plasma membrane PtdIns-4,5-P 2 is important for exocytosis. Expression of PH-GFP also reduced calcium currents, raising the possibility that PtdIns-4,5-P 2 in some manner alters calcium channel function in chromaffin cells.

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The incorporation of 32P into the nucleotides of ribonucleic acid in pigeon pancreas slices

Cited by 46 publications

References 5 publications

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Diglyceride lipase: a pathway for arachidonate release from human platelets.

A Pleckstrin Homology Domain Specific for Phosphatidylinositol 4,5-Bisphosphate (PtdIns-4,5-P2) and Fused to Green Fluorescent Protein Identifies Plasma Membrane PtdIns-4,5-P2 as Being Important in Exocytosis

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