Progesterone-induced phospholipid N-methylation and sphingomyelin synthesis in the amphibian oocyte plasma membrane: a second source of the 1,2-diacylglycerol second messenger associated with the G2/M transition.
The effects of progesterone and GTP gamma S on phospholipid N-methylation and sphingomyelin synthesis were studied in plasma-vitelline membranes isolated from amphibian (Rana pipiens) oocytes. Plasma-vitelline membranes were preincubated with S-adenosyl-L-[methyl-3H]methionine for 2 min at 20 degrees C and total phospholipids extracted at 0, 15, 30 and 60 s after addition of progesterone and/or GTP gamma S. Progesterone levels (3 microM) that induce meiosis in the intact oocyte stimulated [3H-methyl]incorporation into phosphatidylmonomethylethanolamine (PME) 9-10-fold over the first 60 s, with smaller increases in phosphatidyldimethylethanolamine (PDE) and phosphatidylcholine (PC). [methyl-3H] labeling of sphingomyelin (SM) rises after 30 s, approaching that of [methyl-3H]PME by 60 s. 17 beta-Estradiol, a noninducer of meiosis, was inactive. When oocytes were prelabeled with [3H]palmitic acid, it was found that a fall in [3H]ceramide coincides with the transient increase in [3H]SM, indicating that the end product of N-methylation (PC) undergoes a transfer reaction with ceramide to form SM and 1,2-DG. GTP gamma S levels previously reported to stimulate PC-specific phospholipase C activity in oocyte plasma membranes (5 microM) also stimulated both [methyl-3H]PME and [methyl-3H]SM formation. An inhibitor of phospholipid N-methylation, 2-(methyl-amino)ethanol, blocked stimulation of [methyl-3H]SM synthesis by both progesterone and GTP gamma S as well as induction of meiosis by progesterone. Progesterone thus acts at the oocyte plasma membrane to stimulate PE N-methyltransferase and SM synthase. The finding that GTP gamma S mimics progesterone suggests that N-methyltransferase is mediated by G-protein(s). The transient increase in 1,2-DG which we had previously reported to occur within 1-2 min following progesterone stimulation of the Rana oocyte appears to arise from PC by two different pathways: SM synthesis and hydrolysis of PC by phospholipase C.
Morrill
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GA
Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461.
Ma
G Y
GY
Kostellow
A B
AB
D000818:Animals; D002453:Cell Cycle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism*; D016195:G2 Phase; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008745:Methylation; D008938:Mitosis; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D011894:Rana pipiens; D015290:Second Messenger Systems; D013109:Sphingomyelins / Q000096:biosynthesis*
C011439:1,2-diacylglycerol; D004075:Diglycerides; D010169:Palmitic Acids; D010743:Phospholipids; D013109:Sphingomyelins; D019308:Palmitic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011374:Progesterone