| CMP activates reversal of phosphatidylinositol synthase and base exchange by distinct mechanisms in rat pituitary GH3 cells. | |
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MedLine Citation:
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PMID: 2176479 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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CMP is known to activate phosphatidylinositol (PtdIns)/inositol (Ins) base exchange and has been reported to activate reversal of PtdIns synthase also. Because it is possible that PtdIns synthase acting in the reverse direction, followed by re-incorporation of ambient Ins, could be responsible for base-exchange activity, we characterized these processes in rat pituitary GH3 cells. In permeabilized GH3 cells prelabelled with [3H]Ins and incubated in buffer with LiCl but without added Ins, CMP stimulated rapid accumulation of [3H]Ins and decreases in [3H]PtdIns; the Km for CMP was 1.7 mM. CDP and CTP were less effective, whereas 2'-CMP, 3'-CMP, other nucleoside monophosphates and cytidine did not influence this process. In permeabilized cells prelabelled to isotopic equilibrium with [3H]Ins and [32P]Pi, CMP stimulated decreases in both the 32P and 3H labelling of PtdIns, but did not increase that of [32P]phosphatidic acid. These findings demonstrate that in the absence of added Ins the effect of CMP is not via activation of base exchange nor via a phospholipase D, but by reversal of PtdIns synthase. In permeabilized cells prelabelled with [3H]Ins and [32P]Pi, unlabelled Ins inhibited loss of 32P labelling of PtdIns caused by CMP while markedly stimulating loss of 3H labelling of PtdIns and release of [3H]Ins. These data demonstrate that Ins inhibits reversal of PtdIns synthase, but stimulates base exchange. We conclude that in GH3 cells reversal of PtdIns synthase and PtdIns/Ins base exchange are both stimulated by CMP, but are distinct processes. |
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Authors:
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A B Cubitt; M C Gershengorn |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The Biochemical journal Volume: 272 ISSN: 0264-6021 ISO Abbreviation: Biochem. J. Publication Date: 1990 Dec |
Date Detail:
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Created Date: 1991-02-14 Completed Date: 1991-02-14 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 2984726R Medline TA: Biochem J Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 813-6 Citation Subset: IM |
Affiliation:
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Department of Medicine, Cornell University Medical College, New York, NY. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase Cell Line Cytidine / pharmacology Cytidine Diphosphate / pharmacology Cytidine Monophosphate / pharmacology* Cytidine Triphosphate / pharmacology Inositol / metabolism Kinetics Magnesium / pharmacology Membrane Proteins Phosphorus Radioisotopes Phosphotransferases / metabolism* Pituitary Neoplasms Rats Transferases (Other Substituted Phosphate Groups)* Tritium |
| Grant Support | |
ID/Acronym/Agency:
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DK33468/DK/NIDDK NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Membrane Proteins; 0/Phosphorus Radioisotopes; 10028-17-8/Tritium; 63-37-6/Cytidine Monophosphate; 63-38-7/Cytidine Diphosphate; 65-46-3/Cytidine; 65-47-4/Cytidine Triphosphate; 6917-35-7/Inositol; 7439-95-4/Magnesium; EC 2.7.-/Phosphotransferases; EC 2.7.8.-/Transferases (Other Substituted Phosphate Groups); EC 2.7.8.11/CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; EC 2.7.8.11/Cdipt protein, rat |
| Comments/Corrections | |
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