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First published online 8 April 2008
doi: 10.1242/jcs.020081

Journal of Cell Science 121, 1363-1372 (2008)
Published by The Company of Biologists 2008
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Research Article

Caveolin-1 alters Ca2+ signal duration through specific interaction with the G{alpha}q family of G proteins

Parijat Sengupta, Finly Philip* and Suzanne Scarlata{ddagger}

Department of Physiology and Biophysics, BST6-145, Stony Brook University, Stony Brook, NY 11794-8661, USA

{ddagger} Author for correspondence (e-mail: Suzanne.Scarlata{at}sunysb.edu)

Accepted 28 January 2008

Caveolae are membrane domains having caveolin-1 (Cav1) as their main structural component. Here, we determined whether Cav1 affects Ca2+ signaling through the G{alpha}q–phospholipase-Cβ (PLCβ) pathway using Fischer rat thyroid cells that lack Cav1 (FRTcav–) and a sister line that forms caveolae-like domains due to stable transfection with Cav1 (FRTcav+). In the resting state, we found that eCFP-Gβ{gamma} and G{alpha}q-eYFP are similarly associated in both cell lines by Forster resonance energy transfer (FRET). Upon stimulation, the amount of FRET between G{alpha}q-eYFP and eCFP-Gβ{gamma} remains high in FRTcav– cells, but decreases almost completely in FRTcav+ cells, suggesting that Cav1 is increasing the separation between G{alpha}q-Gβ{gamma} subunits. In FRTcav– cells overexpressing PLCβ, a rapid recovery of Ca2+ is observed after stimulation. However, FRTcav+ cells show a sustained level of elevated Ca2+. FRET and colocalization show specific interactions between G{alpha}q and Cav1 that increase upon stimulation. Fluorescence correlation spectroscopy studies show that the mobility of G{alpha}q-eGFP is unaffected by activation in either cell type. The mobility of eGFP-Gβ{gamma} remains slow in FRTcav– cells but increases in FRTcav+ cells. Together, our data suggest that, upon stimulation, G{alpha}q(GTP) switches from having strong interactions with Gβ{gamma} to Cav1, thereby releasing Gβ{gamma}. This prolongs the recombination time for the heterotrimer, thus causing a sustained Ca2+ signal.

Key words: G proteins, Ca2+ signaling, Caveolin-1, Phospholipase C


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