Article

A G(s)-linked receptor maintains meiotic arrest in mouse oocytes, but luteinizing hormone does not cause meiotic resumption by terminating receptor-G(s) signaling.

Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06032, USA.
Developmental Biology (impact factor: 4.07). 11/2007; 310(2):240-9. DOI:10.1016/j.ydbio.2007.07.017 pp.240-9
Source: PubMed

ABSTRACT The maintenance of meiotic prophase arrest in fully grown vertebrate oocytes depends on the activity of a G(s) G-protein that activates adenylyl cyclase and elevates cAMP, and in the mouse oocyte, G(s) is activated by a constitutively active orphan receptor, GPR3. To determine whether the action of luteinizing hormone (LH) on the mouse ovarian follicle causes meiotic resumption by inhibiting GPR3-G(s) signaling, we examined the effect of LH on the localization of Galpha(s). G(s) activation in response to stimulation of an exogenously expressed beta(2)-adrenergic receptor causes Galpha(s) to move from the oocyte plasma membrane into the cytoplasm, whereas G(s) inactivation in response to inhibition of the beta(2)-adrenergic receptor causes Galpha(s) to move back to the plasma membrane. However, LH does not cause a change in Galpha(s) localization, indicating that LH does not act by terminating receptor-G(s) signaling.

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  • Article: Beta-adrenergic receptor stimulation promotes G alpha s internalization through lipid rafts: a study in living cells.
    John A Allen, Jiang Z Yu, Robert J Donati, Mark M Rasenick
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    ABSTRACT: Upon binding hormones or drugs, many G protein-coupled receptors are internalized, leading to receptor recycling, receptor desensitization, and down-regulation. Much less understood is whether heterotrimeric G proteins also undergo agonist-induced endocytosis. To investigate the intracellular trafficking of G alpha s, we developed a functional G alpha s-green fluorescent protein (GFP) fusion protein that can be visualized in living cells during signal transduction. C6 and MCF-7 cells expressing G alpha s-GFP were treated with 10 microM isoproterenol, and trafficking was assessed with fluorescence microscopy. Upon isoproterenol stimulation, G alpha s-GFP was removed from the plasma membrane and internalized into vesicles. Vesicles containing G alpha s-GFP did not colocalize with markers for early endosomes or late endosomes/lysosomes, revealing that G alpha s does not traffic through common endocytic pathways. Furthermore, G alpha s-GFP did not colocalize with internalized beta2-adrenergic receptors, suggesting that G alpha s and receptors are removed from the plasma membrane by distinct endocytic pathways. Nonetheless, activated G alpha s-GFP did colocalize in vesicles labeled with fluorescent cholera toxin B, a lipid raft marker. Agonist significantly increased G alpha s protein in Triton X-100 -insoluble membrane fractions, suggesting that G alpha s moves into lipid rafts/caveolae after activation. Disruption of rafts/caveolae by treatment with cyclodextrin prevented agonist-induced internalization of G alpha s-GFP, as did overexpression of a dominant-negative dynamin. Taken together, these results suggest that receptor-activated G alpha s moves into lipid rafts and is internalized from these membrane microdomains. It is suggested that agonist-induced internalization of G alpha s plays a specific role in G protein-coupled receptor-mediated signaling and could enable G alpha s to traffic into the cellular interior to regulate effectors at multiple cellular sites.
    Molecular Pharmacology 06/2005; 67(5):1493-504. · 4.88 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

activates adenylyl cyclase
 
beta(2)-adrenergic receptor causes Galpha(s)
 
constitutively active orphan receptor
 
cytoplasm
 
GPR3
 
inhibiting GPR3-G(s)
 
inhibition
 
luteinizing hormone
 
meiotic prophase arrest
 
mouse ovarian follicle causes meiotic resumption
 
oocyte plasma membrane
 
plasma membrane
 
terminating receptor-G(s)
 
vertebrate oocytes
 

Rachael P Norris