Nature Cell Biology
7, 405 - 411 (2005)
Published online: 27 March 2005; | doi:10.1038/ncb1237
Spinophilin regulates Ca2+ signalling by binding the N-terminal domain of RGS2 and the third intracellular loop of G-protein-coupled receptorsXinhua Wang1, 7, Weizhong Zeng1, 7, Abigail A. Soyombo1, Wei Tang2, Elliott M. Ross2, Anthony P. Barnes3, Sharon L. Milgram3, Josef M. Penninger4, Patrick B. Allen5, Paul Greengard6
& Shmuel Muallem11
Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9040, USA. 2
Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9040, USA. 3
The Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB7090, Chapel Hill, NC 27599-7090, USA. 4
IMBA (Institute of Molecular Biotechnology of the Austrian Academy of Sciences), Dr Bohr-gasse3-5, Vienna A-1030, Austria. 5
Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA. 6
Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, New York 10021, USA. 7
These authors contributed equally to this work.
Correspondence should be addressed to Shmuel Muallem SHMUEL.MUALLEM@utsouthwestern.eduSignalling by G proteins is controlled by the regulator of G-protein signalling (RGS) proteins that accelerate the GTPase activity of G subunits and act in a G-protein-coupled receptor (GPCR)-specific manner1,
2,
3,
4. The conserved RGS domain accelerates the G subunit GTPase activity5, whereas the variable amino-terminal domain participates in GPCR recognition6. How receptor recognition is achieved is not known. Here, we show that the scaffold protein spinophilin (SPL)7, which binds the third intracellualar loop (3iL) of several GPCRs8,
9,
10, binds the N-terminal domain of RGS2. SPL also binds RGS1, RGS4, RGS16 and GAIP. When expressed in Xenopus laevis oocytes, SPL markedly increased inhibition of -adrenergic receptor (AR) Ca2+ signalling by RGS2. Notably, the constitutively active mutant ARA293E (the mutation being in the 3iL) did not bind SPL and was relatively resistant to inhibition by RGS2. Use of  AR−AR chimaeras identified the 288REKKAA293 sequence as essential for the binding of SPL and inhibition of Ca2+ signalling by RGS2. Furthermore, AR-evoked Ca2+ signalling is less sensitive to inhibition by SPL in rgs2-/- cells and less sensitive to inhibition by RGS2 in spl-/- cells. These findings provide a general mechanism by which RGS proteins recognize GPCRs to confer signalling specificity.
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