Atorvastatin desensitizes beta-adrenergic signaling in cardiac myocytes via reduced isoprenylation of G-protein gamma-subunits.
Statins exert pleiotropic, cholesterol-independent effects by reducing isoprenylation of monomeric GTPases. Here we examined whether statins also reduce isoprenylation of gamma-subunits of heterotrimeric G-proteins and thereby affect beta-adrenergic signaling and regulation of force in cardiac myocytes. Neonatal rat cardiac myocytes (NRCM) were treated with atorvastatin (0.1-10 micromol/l; 12-48 h) and examined for adenylyl cyclase regulating G-protein alpha- (Galpha), beta- (Gbeta), and gamma- (Ggamma) subunits and cAMP accumulation. Engineered heart tissue (EHT) from NRCM was used to evaluate contractile consequences. In atorvastatin-treated NRCM, a second band of Ggamma3 with a lower apparent molecular weight appeared in cytosol and particulate fractions that was absent in vehicle-treated NRCM, but also seen after GGTI-298, a geranylgeranyl transferase inhibitor. In parallel, Gbeta accumulated in the cytosol and total cellular content of Galphas was reduced. In atorvastatin-treated NRCM, the cAMP-increasing effect of isoprenaline was reduced. Likewise, the positive inotropic effect of isoprenaline was desensitized and reduced after treatment with atorvastatin. The effects of atorvastatin were abolished by mevalonate and/or geranylgeranyl pyrophosphate, but not by farnesyl pyrophosphate or squalene. Taken together, the results of this study show that atorvastatin desensitizes NRCM to beta-adrenergic stimulation by a mechanism that involves reduced isoprenylation of Ggamma and subsequent reductions in the cellular content of Galphas.
Institute of Experimental and Clinical Pharmacology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Ulrike
U
Mühlhäuser
Oliver
O
Zolk
Thomas
T
Rau
Felix
F
Münzel
Thomas
T
Wieland
Thomas
T
Eschenhagen
D000818:Animals; D000069059:Atorvastatin; D002478:Cells, Cultured; D000242:Cyclic AMP; D044388:GTP-Binding Protein gamma Subunits / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D006538:Heptanoic Acids / Q000494:pharmacology*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D017368:Protein Prenylation / Q000187:drug effects*; D021122:Protein Subunits; D011758:Pyrroles / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*
D044388:GTP-Binding Protein gamma Subunits; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D021122:Protein Subunits; D011758:Pyrroles; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D000069059:Atorvastatin; D000242:Cyclic AMP