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Differential regulation of G protein‐gated inwardly rectifying K + channel kinetics by distinct domains of RGS8
Author(s) -
Jeong SeongWoo,
Ikeda Stephen R.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00335.x
Subject(s) - g protein coupled inwardly rectifying potassium channel , g protein , heterotrimeric g protein , microbiology and biotechnology , pertussis toxin , chemistry , pas domain , g protein coupled receptor , biophysics , gtpase activating protein , gi alpha subunit , g beta gamma complex , gtp binding protein regulators , biology , signal transduction , biochemistry , gene , transcription factor
1 The contribution of endogenous regulators of G protein signalling (RGS) proteins to G protein modulated inwardly rectifying K + channel (GIRK) activation/deactivation was examined by expressing mutants of Gα oA insensitive to both pertussis toxin (PTX) and RGS proteins in rat sympathetic neurons. 2 GIRK channel modulation was reconstituted in PTX‐treated rat sympathetic neurons following heterologous expression of G protein subunits. Under these conditions, noradrenaline‐evoked GIRK channel currents displayed: (1) a prominent lag phase preceding activation, (2) retarded activation and deactivation kinetics, and (3) a lack of acute desensitization. 3 Unexpectedly, heterologous expression of RGS8 in neurons expressing PTX‐i‐RGS‐insensitive Gα oA shortened the lag phase and restored rapid activation, but retarded the deactivation phase further. These effects were found to arise from the N‐terminus, but not the core domain, of RGS8 thus suggesting actions on channel modulation independently of GTPase acceleration. 4 These findings indicate that different domains of RGS8 make distinct contributions to the temporal regulation of GIRK channels. The RGS8 core domain accelerates termination of the G‐protein cycle presumably by increasing Gα GTPase activity. In contrast, the N‐terminal domain of RGS8 appears to promote entry into the G protein cycle, possibly by enhancing coupling of receptors to the G protein heterotrimer. Together, these opposing effects should allow for an increase in temporal fidelity without a dramatic decrease in signal strength.