Luteinizing hormone/choriogonadotropin receptor-mediated activation of heterotrimeric guanine nucleotide binding proteins in ovarian follicular membranes.
The LH/CG receptor signals to adenylyl cyclase via the stimulatory heterotrimeric GTP binding regulatory protein, Gs, and to phospholipase C and potentially to other effectors, such as ion channels, via a G protein or proteins that have not been identified in gonadal cells. To identify G proteins activated in a physiological membrane environment upon LH/CG receptor activation, we used the ability of activated G proteins to bind GTP and incubated ovarian follicular membranes with the photoaffinity GTP analog, P3-(4-azidoanilido)-P1-5'-GTP ([32P]AAGTP). Results showed that human CG (hCG) stimulated the binding of [32P]AAGTP to a 45-kDa protein(s) in follicular membranes that comigrated with immunoreactive G alphas, G alphaq/11, and G alpha13. When G alpha proteins were immunoprecipitated from Triton X-100 solubilized membrane extracts after photoaffinity labeling with [32P]AAGTP, a time-dependent increase in hCG-dependent [32P]AAGTP binding to G alphas, G alphaq/11, and G alphai was detected. hCG-dependent [32P]AAGTP binding to G alpha13 was also detected. These results demonstrate that agonist-dependent LH/CG receptor activation promotes the activation of Gs, Gi, Gq/11, and G13 in porcine ovarian follicular membranes. These results further suggest that G alphas remains coupled to the agonist-bound LH/CG receptor during at least the initial 10 min after agonist-dependent receptor activation.
Rajagopalan-Gupta
R M
RM
Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Lamm
M L
ML
Mukherjee
S
S
Rasenick
M M
MM
Hunzicker-Dunn
M
M
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000345:Affinity Labels; D001386:Azides; D015153:Blotting, Western; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008566:Membranes / Q000378:metabolism; D006080:Ovarian Follicle / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism*; D011233:Precipitin Tests; D011974:Receptors, LH / Q000378:metabolism*
D000345:Affinity Labels; D001386:Azides; D006063:Chorionic Gonadotropin; D008565:Membrane Proteins; D011974:Receptors, LH; D000246:Adenosine Diphosphate Ribose; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go