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The RGS2 Gene Product from a Candidate Hypertension Allele Shows Decreased Plasma Membrane Association and Inhibition of G_q

Department of Physiology, Heart and Stroke/Richard Lewar Centre of Excellence in Cardiovascular Research, University of Toronto, Toronto, Ontario, Canada

Hypertension is a leading risk factor for the development of cardiovascular disease. Data from human and animal studies suggest that RGS2, a potent inhibitor of G_q signaling, is important for blood pressure regulation. Several RGS2 mutations in the Japanese population have been found to be associated with hypertension. The product of one of these alleles, R44H, is mutated within the amino terminal amphipathic -helix domain, the region responsible for plasma membrane-targeting. The functional consequence of this mutation and its potential link to the development of hypertension, however, are not known. In this study, we showed that R44H was a weaker inhibitor of receptor-mediated G_q signaling than wild-type RGS2. Confocal microscopy revealed that YFP-tagged R44H bound to the plasma membrane less efficiently than wild-type RGS2. R44 is one of the basic residues positioned to stabilize lipid bilayer interaction of the RGS2 amphipathic helix domain. Tryptophan fluorescence and circular dichroism studies of this domain showed that the R44H mutation prevented proper entrenchment of hydrophobic residues into the lipid bilayer without disrupting helix-forming capacity. Together, these data suggest that decreasing the side-chain length and flexibility at R44 prevented proper lipid bilayer association and function of RGS2. Finally, the R44H protein did not behave as a dominant-negative interfering mutant. Thus, our data are consistent with the notion that a R44H missense mutation in human RGS2 produces a hypomorphic allele that may lead to altered receptor-mediated G_q inhibition and contribute to the development of hypertension in affected subjects.

Received for publication December 11, 2007.

Accepted for publication January 23, 2008.

Address correspondence to: Scott P. Heximer, University of Toronto, Rm 3334 MSB, 1 King's College Circle, Toronto, ON, Canada M5S 1A8. E-mail: scott.heximer{at}utoronto.ca

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