A Role for G-Proteins in Directing G-Protein-Coupled Receptor鈥揅aveolae Localization

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• 作者：Rhodora Cristina Calizo ; Suzanne Scarlata
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：November 27, 2012
• 年：2012
• 卷：51
• 期：47
• 页码：9513-9523
• 全文大小：508K
• 年卷期：v.51,no.47(November 27, 2012)
• ISSN：1520-4995

文摘

Caveolae are membrane domains that may influence cell signaling by sequestering specific proteins such as G-protein-coupled receptors (GPCRs). While previous reports largely show that G伪_q subunits, but not other G-proteins, interact strongly with the caveolae protein, Caveolin-1 (Cav1), the inclusion of GPCRs in caveolae is controversial. Here, we have used fluorescence methods to determine the effect of caveolae on the physical and functional properties of two GPCRs that have been reported to reside in caveolae, bradykinin receptor type 2 (B₂R), which is coupled to G伪_q, and the 渭-opioid receptor (渭OR), which is coupled to G伪_i. While caveolae do not affect cAMP signals mediated by 渭OR, they prolong Ca²⁺ signals mediated by B₂R. In A10 cells that endogenously express B₂R and Cav1, downregulation of Cav1 ablates the prolonged recovery seen upon bradykinin stimulation in accord with the idea that the presence of caveolae prolongs G伪_q activation. Immunofluorescence and F枚rster resonance energy transfer (FRET) studies show that a significant fraction of B₂R resides at or close to caveolae domains while none or very little 渭OR resides in caveolae domains. The level of FRET between B₂R and caveolae is reduced by downregulation of G伪_q or by addition of a peptide that interferes with G伪_q鈥揅aveolin-1 interactions, suggesting that G伪_q promotes localization of B₂R to caveolae domains. Our results lead to the suggestion that G伪_q can localize its associated receptors to caveolae domains to enhance their signals.