title: Gi proteins mediate activation of the canonical hedgehog pathway in the myocardium.
abstract: During myocardial ischemia, upregulation of the hedgehog (Hh) pathway promotes neovascularization and increases cardiomyocyte survival. The canonical Hh pathway activates a transcriptional program through the Gli family of transcription factors by derepression of the seven-transmembrane protein smoothened (Smo). The mechanisms linking Smo to Gli are complex and, in some cell types, involve coupling of Smo to Gi proteins. In the present study, we investigated, for the first time, the transcriptional response of cardiomyocytes to sonic hedgehog (Shh) and the role of Gi protein utilization. Our results show that Shh strongly activates Gli1 expression by quantitative PCR in a Smo-dependent manner in neonatal rat ventricular cardiomyocytes. Microarray analysis of gene expression changes elicited by Shh and sensitive to a Smo inhibitor identified a small subset of 37 cardiomyocyte-specific genes regulated by Shh, including some in the PKA and purinergic signaling pathways. In addition, neonatal rat ventricular cardiomyocytes infected with an adenovirus encoding GiCT, a peptide that impairs receptor-Gi protein coupling, showed reduced activation of Hh targets. In vitro data were confirmed in transgenic mice with cardiomyocyte-inducible GiCT expression. Transgenic GiCT mice showed specific reduction of Gli1 expression in the heart under basal conditions and failed to upregulate the Hh pathway upon ischemia and reperfusion injury, unlike their littermate controls. This study characterizes, for the first time, the transcriptional response of cardiomyocytes to Shh and establishes a critical role for Smo coupling to Gi in Hh signaling in the normal and ischemic myocardium.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania;
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Carbe
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania;
authors.forename: Lan
authors.initials: L
authors.lastname: Cheng
authors.affiliation: Department of Cancer Biology, Thomas Jefferson University, Philadelphia, Pennsylvania; Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania.
authors.forename: Sankar
authors.initials: S
authors.lastname: Addya
authors.affiliation: Department of Pharmacology and Center for Translational Medicine, Temple University, Philadelphia, Pennsylvania; and.
authors.forename: Jessica I
authors.initials: JI
authors.lastname: Gold
authors.affiliation: Department of Pharmacology and Center for Translational Medicine, Temple University, Philadelphia, Pennsylvania; and.
authors.forename: Erhe
authors.initials: E
authors.lastname: Gao
authors.affiliation: Department of Pharmacology and Center for Translational Medicine, Temple University, Philadelphia, Pennsylvania; and.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Koch
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania; Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania Natalia.riobo@jefferson.edu.
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Riobo
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000378:metabolism*; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D008822:Mice, Transgenic; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015398:Signal Transduction; D000072086:Smoothened Receptor; D000071676:Zinc Finger Protein GLI1
chemical_list: C498520:Gli1 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D043562:Receptors, G-Protein-Coupled; C491022:Smo protein, mouse; D000072086:Smoothened Receptor; D000071676:Zinc Finger Protein GLI1; D019206:GTP-Binding Protein alpha Subunits, Gi-Go
keywords: G proteins; heart failure; hedgehog; smoothened