Meiotic resumption in response to luteinizing hormone is independent of a Gi family G protein or calcium in the mouse oocyte.
The signaling pathway by which luteinizing hormone (LH) acts on the somatic cells of vertebrate ovarian follicles to stimulate meiotic resumption in the oocyte requires a decrease in cAMP in the oocyte, but how cAMP is decreased is unknown. Activation of Gi family G proteins can lower cAMP by inhibiting adenylate cyclase or stimulating a cyclic nucleotide phosphodiesterase, but we show here that inhibition of this class of G proteins by injection of pertussis toxin into follicle-enclosed mouse oocytes does not prevent meiotic resumption in response to LH. Likewise, elevation of Ca2+ can lower cAMP through its action on Ca2+-sensitive adenylate cyclases or phosphodiesterases, but inhibition of a Ca2+ rise by injection of EGTA into follicle-enclosed mouse oocytes does not inhibit the LH response. Thus, neither of these well-known mechanisms of cAMP regulation can account for LH signaling to the oocyte in the mouse ovary.
Mehlmann
Lisa M
LM
Department of Cell Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06032, USA. lmehlman@neuron.uchc.edu
Kalinowski
Rebecca R
RR
Ross
Lavinia F
LF
Parlow
Albert F
AF
Hewlett
Erik L
EL
Jaffe
Laurinda A
LA
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors / Q000502:physiology*; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000502:physiology*; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D037342:Pertussis Toxin / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D015398:Signal Transduction
D002614:Chelating Agents; D004533:Egtazic Acid; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010727:Phosphoric Diester Hydrolases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium