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Regulation of meiotic prophase arrest in mouse oocytes by GPR3, a constitutive activator of the Gs G protein.

Freudzon L, Norris RP, Hand AR, Tanaka S, Saeki Y, Jones TL, Rasenick MM, Berlot CH, Mehlmann LM, Jaffe LA - J. Cell Biol. (2005)

Bottom Line: GPR3 decreased the ratio of Galpha(s) in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Galpha(s) in the oocyte.However, GPR3-dependent G(s) activity was similar in follicle-enclosed and follicle-free oocytes.Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06032.

ABSTRACT
The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein G(s) and an orphan member of the G protein-coupled receptor family, GPR3. To determine whether GPR3 activates G(s), the localization of Galpha(s) in follicle-enclosed oocytes from Gpr3(+/+) and Gpr3(-/-) mice was compared by using immunofluorescence and Galpha(s)GFP. GPR3 decreased the ratio of Galpha(s) in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Galpha(s) in the oocyte. Both of these properties indicate that GPR3 activates G(s). The follicle cells around the oocyte are also necessary to keep the oocyte in prophase, suggesting that they might activate GPR3. However, GPR3-dependent G(s) activity was similar in follicle-enclosed and follicle-free oocytes. Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.

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GαsGFP fluorescence in Gpr3+/+ and Gpr3−/− oocytes that were isolated from preantral follicles and injected with GαsGFP RNA. (A and B) Gpr3+/+ and Gpr3−/− oocytes. The confocal microscope settings and bars were the same for A and B. (C) Plasma membrane-to-cytoplasm fluorescence ratios for Gpr3+/+ (8.8 ± 0.8) and Gpr3−/− oocytes (21.8 ± 1.2). Mean ± SEM (error bars; n = number of oocytes). The ratios for Gpr3+/+ and Gpr3−/− oocytes were significantly different (t test, P < 0.0001). Data are from two Gpr3+/+ and two Gpr3−/− mice.
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fig6: GαsGFP fluorescence in Gpr3+/+ and Gpr3−/− oocytes that were isolated from preantral follicles and injected with GαsGFP RNA. (A and B) Gpr3+/+ and Gpr3−/− oocytes. The confocal microscope settings and bars were the same for A and B. (C) Plasma membrane-to-cytoplasm fluorescence ratios for Gpr3+/+ (8.8 ± 0.8) and Gpr3−/− oocytes (21.8 ± 1.2). Mean ± SEM (error bars; n = number of oocytes). The ratios for Gpr3+/+ and Gpr3−/− oocytes were significantly different (t test, P < 0.0001). Data are from two Gpr3+/+ and two Gpr3−/− mice.

Mentions: Oocytes were isolated from Gpr3+/+ and Gpr3−/− preantral follicles, injected with GαsGFP RNA, cultured overnight, and imaged by confocal microscopy. The difference in GαsGFP localization between Gpr3+/+ and Gpr3−/− oocytes was still evident, indicating that GPR3 activates Gs even in the absence of follicle cells (Fig. 6).


Regulation of meiotic prophase arrest in mouse oocytes by GPR3, a constitutive activator of the Gs G protein.

Freudzon L, Norris RP, Hand AR, Tanaka S, Saeki Y, Jones TL, Rasenick MM, Berlot CH, Mehlmann LM, Jaffe LA - J. Cell Biol. (2005)

GαsGFP fluorescence in Gpr3+/+ and Gpr3−/− oocytes that were isolated from preantral follicles and injected with GαsGFP RNA. (A and B) Gpr3+/+ and Gpr3−/− oocytes. The confocal microscope settings and bars were the same for A and B. (C) Plasma membrane-to-cytoplasm fluorescence ratios for Gpr3+/+ (8.8 ± 0.8) and Gpr3−/− oocytes (21.8 ± 1.2). Mean ± SEM (error bars; n = number of oocytes). The ratios for Gpr3+/+ and Gpr3−/− oocytes were significantly different (t test, P < 0.0001). Data are from two Gpr3+/+ and two Gpr3−/− mice.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2171177&req=5

fig6: GαsGFP fluorescence in Gpr3+/+ and Gpr3−/− oocytes that were isolated from preantral follicles and injected with GαsGFP RNA. (A and B) Gpr3+/+ and Gpr3−/− oocytes. The confocal microscope settings and bars were the same for A and B. (C) Plasma membrane-to-cytoplasm fluorescence ratios for Gpr3+/+ (8.8 ± 0.8) and Gpr3−/− oocytes (21.8 ± 1.2). Mean ± SEM (error bars; n = number of oocytes). The ratios for Gpr3+/+ and Gpr3−/− oocytes were significantly different (t test, P < 0.0001). Data are from two Gpr3+/+ and two Gpr3−/− mice.
Mentions: Oocytes were isolated from Gpr3+/+ and Gpr3−/− preantral follicles, injected with GαsGFP RNA, cultured overnight, and imaged by confocal microscopy. The difference in GαsGFP localization between Gpr3+/+ and Gpr3−/− oocytes was still evident, indicating that GPR3 activates Gs even in the absence of follicle cells (Fig. 6).

Bottom Line: GPR3 decreased the ratio of Galpha(s) in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Galpha(s) in the oocyte.However, GPR3-dependent G(s) activity was similar in follicle-enclosed and follicle-free oocytes.Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06032.

ABSTRACT
The arrest of meiotic prophase in mouse oocytes within antral follicles requires the G protein G(s) and an orphan member of the G protein-coupled receptor family, GPR3. To determine whether GPR3 activates G(s), the localization of Galpha(s) in follicle-enclosed oocytes from Gpr3(+/+) and Gpr3(-/-) mice was compared by using immunofluorescence and Galpha(s)GFP. GPR3 decreased the ratio of Galpha(s) in the oocyte plasma membrane versus the cytoplasm and also decreased the amount of Galpha(s) in the oocyte. Both of these properties indicate that GPR3 activates G(s). The follicle cells around the oocyte are also necessary to keep the oocyte in prophase, suggesting that they might activate GPR3. However, GPR3-dependent G(s) activity was similar in follicle-enclosed and follicle-free oocytes. Thus, the maintenance of prophase arrest depends on the constitutive activity of GPR3 in the oocyte, and the follicle cell signal acts by a means other than increasing GPR3 activity.

Show MeSH
Related in: MedlinePlus