A G protein-coupled receptor kinase induces Xenopus oocyte maturation.
Several recent studies have suggested that resumption of oocyte meiosis, indicated by germinal vesicle breakdown or GVBD, involves inhibition of endogenous heterotrimeric G proteins in both frogs and mice. These studies imply that a heterotrimeric G protein(s), and hence its upstream activator (a G protein-coupled receptor or GpCR), is activated in prophase oocytes and is responsible for maintaining meiosis arrest. To test the existence and function of this putative GpCR, we utilized a mammalian G-protein-coupled receptor kinase (GRK3) and beta-arrestin-2, which together are known to cause GpCR desensitization. Injection of mRNA for rat GRK3 caused hormone-independent GVBD. The kinase activity of GRK3 was essential for GVBD induction as its kinase-dead mutant (GRK3-K220R) was completely ineffective. Another GRK3 mutant (GRK3-DeltaC), which lacked the C-terminal G(betagamma)-binding domain and which was not associated with oocyte membranes, also failed to induce GVBD. Furthermore, injection of rat beta-arrestin-2 mRNA also induced hormone-independent GVBD. Several inhibitors of clathrin-mediated receptor endocytosis (the clathrin-binding domain of beta-arrestin-2, concanavalin A, and monodansyl cadaverine) significantly reduced the abilities of GRK3/beta-arrestin-2 to induce GVBD. These results support the central role of a yet-unidentified GpCR in maintaining prophase arrest in frog oocytes and provide a potential means for its molecular identification.
Wang
Jing
J
Ottawa Health Research Institute, Ottawa Hospital Civic Campus, 725 Parkdale Avenue, Ottawa, Ontario K1Y 4E9, Canada.
Liu
X Johné
XJ
D000818:Animals; D019390:Arrestins / Q000502:physiology*; D002966:Clathrin / Q000502:physiology; D005260:Female; D054770:G-Protein-Coupled Receptor Kinase 3; D019204:GTP-Binding Proteins / Q000502:physiology; D009865:Oocytes / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D051381:Rats; D014981:Xenopus; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605258:Arrb2 protein, mouse; C000605257:Arrb2 protein, rat; D019390:Arrestins; D002966:Clathrin; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D011374:Progesterone; D017346:Protein Serine-Threonine Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C517851:Grk3 protein, rat; D019204:GTP-Binding Proteins