| First Author | DeGeorge BR Jr | Year | 2008 |
| Journal | Circulation | Volume | 117 |
| Issue | 11 | Pages | 1378-87 |
| PubMed ID | 18316484 | Mgi Jnum | J:214939 |
| Mgi Id | MGI:5604227 | Doi | 10.1161/CIRCULATIONAHA.107.752618 |
| Citation | DeGeorge BR Jr, et al. (2008) Targeted inhibition of cardiomyocyte Gi signaling enhances susceptibility to apoptotic cell death in response to ischemic stress. Circulation 117(11):1378-87 |
| abstractText | BACKGROUND: A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein alpha subunit, G alpha(i2). It has not been determined conclusively whether increased Gi activity in the heart is beneficial or deleterious in vivo. Gi signaling has been implicated in the mechanism of cardioprotective agents; however, no in vivo evidence exists that any of the G alpha subunits are cardioprotective. We have created a novel molecular tool to specifically address the role of Gi proteins in normal and dysfunctional myocardium. METHODS AND RESULTS: We have developed a class-specific Gi inhibitor peptide, GiCT, composed of the region of G alpha(i2) that interacts specifically with G protein-coupled receptors. GiCT inhibits Gi signals specifically in vitro and in vivo, whereas Gs and Gq signals are not affected. In vivo expression of GiCT in transgenic mice effectively causes a "functional knockout" of cardiac G alpha(i2) signaling. Inducible, cardiac-specific GiCT transgenic mice display a baseline phenotype consistent with nontransgenic mice. However, when subjected to ischemia/reperfusion injury, GiCT transgenic mice demonstrate a significant increase in infarct size compared with nontransgenic mice (from 36.9+/-2.5% to 50.9+/-4.3%). Mechanistically, this post-ischemia/reperfusion phenotype includes increased myocardial apoptosis and resultant decreased contractile performance. CONCLUSIONS: Overall, our results demonstrate the in vivo utility of GiCT to dissect specific mechanisms attributed to Gi signaling in stressed myocardium. Our results with GiCT indicate that upregulation of G alpha(i2) is an adaptive protective response after ischemia to shield myocytes from apoptosis. |
