5'-CMP stimulates phospholipase A-mediated hydrolysis of phosphatidylinositol in permeabilized pituitary GH3 cells.
We showed previously that 5'-CMP activates PtdIns-Ins base exchange and reversal PtdIns synthase in permeabilized rat pituitary GH3 cells. Here we report another effect of 5'-CMP on PtdIns metabolism in these cells. In permeabilized GH3 cells prelabelled with [3H]Ins and incubated in buffer with LiCl and a free Ca2+ concentration of 0.1 microM but without added Ins, 5'-CMP stimulated formation of glycerophospho[3H]inositol (GroP[3H]Ins) after a lag period of at least 5 min. This effect was concentration-dependent; the apparent Km was 0.30 +/- 0.02 mM. CDP and CTP stimulated GroPIns formation less effectively than did 5'-CMP, but cytidine, 2'-CMP, 3'-CMP, 5'-AMP and 5'-GMP had no effect. 5'-CMP stimulated formation of lysoPtdIns also. In permeabilized GH3 cells prelabelled with [3H]arachidonic acid, 5'-CMP stimulated release of [3H]arachidonic acid without a measurable lag period. These data show that 5'-CMP stimulates a phospholipase A activity in permeabilized GH3 cells that hydrolyses PtdIns.
Cubitt
A B
AB
Department of Medicine, Cornell University Medical College, New York, NY.
Thaw
C N
CN
Gershengorn
M C
MC
D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability; D003565:Cytidine Diphosphate / Q000494:pharmacology; D003568:Cytidine Monophosphate / Q000494:pharmacology*; D003570:Cytidine Triphosphate / Q000494:pharmacology; D006868:Hydrolysis; D007295:Inositol Phosphates; D007700:Kinetics; D010716:Phosphatidylinositols / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D010742:Phospholipid Ethers / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects / Q000201:enzymology*; D051381:Rats
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D010742:Phospholipid Ethers; C014575:glycerylphosphoinositol; D003565:Cytidine Diphosphate; D003570:Cytidine Triphosphate; D010741:Phospholipases A; D003568:Cytidine Monophosphate