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Investigation of the novel G protein heterodimer; the G β5 ‐RGS7 complex
Author(s) -
Sandiford Simone Laura,
Narayanan Vijaya,
Wang Qiang,
Slepak Vladlen
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a916-d
Subject(s) - gtpase activating protein , g protein , förster resonance energy transfer , protein subunit , heterotrimeric g protein , microbiology and biotechnology , chemistry , signal transduction , biophysics , biology , biochemistry , fluorescence , gene , physics , quantum mechanics
G protein coupled receptors are part of an important signal transduction pathway with major clinical significance. Regulators of G protein signaling (RGS) proteins accelerate the deactivation of G proteins by acting as GTPase activating proteins (GAPs) towards G α subunits. The R7 subfamily of RGS proteins contain a Gγ like (GGL) domain which allows these proteins to interact with the neurospecific G β subunit, G β5 . In vivo, RGS7, a member of this family is always found in complex with G β5 and this dimer has been shown to act as a GAP towards various G α subunits. Although no GAP activity towards G αq has ever been detected in vitro, using the ratiometric Ca 2+ indicator dye Fura 2AM, we confirm that the RGS7‐G β5 complex attenuates G αq signaling in a receptor specific manner. In addition to the catalytic RGS domain and the GGL domain, all R7 family members also contain the poorly characterized DEP domain. Using fluorescence resonance energy transfer (FRET) spectroscopy and GST pulldown assays we show that there is a novel intramolecular interaction between the DEP domain of RGS7 and the G β5 subunit. This interaction is specific for RGS7 DEP as it does not occur between the RGS9 DEP domain and the G β5 subunit. Here we demonstrate that the DEP‐G β5 binding can be disrupted using site directed mutagenesis. We hypothesize that the RGS7 protein exists in at least two conformations, a “closed” state where it interacts with G β5 and an “open” state where the DEP domain interacts with other proteins. This research is supported by NIH grants GM 060019 and NEI 012982 (V.Z.S.).