Conditional disruption of interactions between G[alpha]i2 and regulator of G protein signaling (RGS) proteins protects the heart from ischemic injury

• Published in: BMC pharmacology & toxicology 2014-06, Vol.15
• Main Authors: Parra, Sergio, Huang, Xinyan, Charbeneau, Raelene A, Wade, Susan M, Kaur, Kuljeet, Rorabaugh, Boyd R, Neubig, Richard R
• Format: Article
• Language: English
• Subjects: Analysis; Cyclic adenylic acid; G proteins; Hydrolysis; Physiological aspects; Proteins
• ISSN: 2050-6511; 2050-6511
• DOI: 10.1186/2050-6511-15-29

Background Regulator of G protein signaling (RGS) proteins suppress G protein coupled receptor signaling by catalyzing the hydrolysis of G[alpha]-bound guanine nucleotide triphosphate. Transgenic mice in which RGS-mediated regulation of G[alpha].sub.i2 is lost (RGS insensitive G[alpha].sub.i2.sup.G184S) exhibit beneficial (protection against ischemic injury) and detrimental (enhanced fibrosis) cardiac phenotypes. This mouse model has revealed the physiological significance of RGS/G[alpha].sub.i2 interactions. Previous studies of the G[alpha].sub.i2.sup.G184S mutation used mice that express this mutant protein throughout their lives. Thus, it is unclear whether these phenotypes result from chronic or acute G[alpha].sub.i2.sup.G184S expression. We addressed this issue by developing mice that conditionally express G[alpha].sub.i2.sup.G184S. Methods Mice that conditionally express RGS insensitive G[alpha].sub.i2.sup.G184S were generated using a floxed minigene strategy. Conditional expression of G[alpha].sub.i2.sup.G184S was characterized by reverse transcription polymerase chain reaction and by enhancement of agonist-induced inhibition of cAMP production in isolated cardiac fibroblasts. The impact of conditional RGS insensitive G[alpha].sub.i2.sup.G184S expression on ischemic injury was assessed by measuring contractile recovery and infarct sizes in isolated hearts subjected to 30 min ischemia and 2 hours reperfusion. Results We demonstrate tamoxifen-dependent expression of G[alpha].sub.i2.sup.G184S, enhanced inhibition of cAMP production, and cardioprotection from ischemic injury in hearts conditionally expressing G[alpha].sub.i2.sup.G184S. Thus the cardioprotective phenotype previously reported in mice expressing G[alpha].sub.i2.sup.G184S does not require embryonic or chronic G[alpha].sub.i2.sup.G184S expression. Rather, cardioprotection occurs following acute (days rather than months) expression of G[alpha].sub.i2.sup.G184S. Conclusions These data suggest that RGS proteins might provide new therapeutic targets to protect the heart from ischemic injury. We anticipate that this model will be valuable for understanding the time course (chronic versus acute) and mechanisms of other phenotypic changes that occur following disruption of interactions between G[alpha].sub.i2 and RGS proteins. Keywords: G protein coupled receptors, Ischemia-reperfusion, Cre-LoxP, Mutation, cAMP inhibition, Regulator of G protein signaling, RGS