Maturation-associated increase in IP3 receptor type 1: role in conferring increased IP3 sensitivity and Ca2+ oscillatory behavior in mouse eggs.
Maturation of mouse oocytes is accompanied by an increase in sensitivity to inositol 1,4,5-trisphosphate (IP(3))-mediated release of intracellular calcium. To test the hypothesis that the maturation-associated 1.5- to 2.0-fold increase in the mass of the type 1 IP(3) receptor (IP(3)R-1) confers this increase in IP(3) sensitivity, we employed RNA interference to prevent this change in IP(3)R-1 protein level. Microinjection into germinal vesicle (GV)-intact oocytes of dsRNA corresponding to the IP(3)R-1 sequence resulted in a >90% reduction in the amount of maternal IP(3)R-1 mRNA and prevented the maturation-associated increase in the mass of the IP(3)R-1 protein. These injected oocytes matured to metaphase II, and there was no effect on the maturation-associated increases in p34(cdc2)/cyclin B kinase and MAP kinase activities or the global pattern of protein synthesis. IP(3)-induced cortical granule exocytosis was significantly decreased in these eggs when compared with controls previously injected with enhanced green fluorescent protein (EGFP) dsRNA. Following insemination, the IP(3)R-1 dsRNA-injected eggs displayed significantly fewer Ca(2+) transients than controls, and the duration of the first Ca(2+) transient was about half that of controls. These results support the hypothesis that the maturation-associated increase in the mass of IP(3)R-1 confers the increase in IP(3)-sensitivity that is observed following oocyte maturation and is necessary for the proper Ca(2+) oscillatory pattern following insemination.
Xu
Zhe
Z
Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
Williams
Carmen J
CJ
Kopf
Gregory S
GS
Schultz
Richard M
RM
D000818:Animals; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000502:physiology*; D010063:Ovum / Q000378:metabolism*; D012330:RNA, Double-Stranded / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D012330:RNA, Double-Stranded; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium