Removal of the N-terminal extension of cardiac troponin I as a functional compensation for impaired myocardial beta-adrenergic signaling.
Although beta-adrenergic stimuli are essential for myocardial contractility, beta-blockers have a proven beneficial effect on the treatment of heart failure, but the mechanism is not fully understood. The stimulatory G protein alpha-subunit (Gsalpha) couples the beta-adrenoreceptor to adenylyl cyclase and the intracellular cAMP response. In a mouse model of conditional Gsalpha deficiency in the cardiac muscle (Gsalpha-DF), we demonstrated heart failure phenotypes accompanied by increases in the level of a truncated cardiac troponin I (cTnI-ND) from restricted removal of the cTnI-specific N-terminal extension. To investigate the functional significance of the increase of cTnI-ND in Gsalpha-DF cardiac muscle, we generated double transgenic mice to overexpress cTnI-ND in Gsalpha-DF hearts. The overexpression of cTnI-ND in Gsalpha-DF failing hearts increased relaxation velocity and left ventricular end diastolic volume to produce higher left ventricle maximum pressure and stroke volume. Supporting the hypothesis that up-regulation of cTnI-ND is a compensatory rather than a destructive myocardial response to impaired beta-adrenergic signaling, the aberrant expression of beta-myosin heavy chain in adult Gsalpha-DF but not control mouse hearts was reversed by cTnI overexpression. These data indicate that the up-regulation of cTnI-ND may partially compensate for the cardiac inefficiency in impaired beta-adrenergic signaling.
Feng
Han-Zhong
HZ
Section of Molecular Cardiology, Evanston Northwestern Healthcare and Northwestern University Feinberg School of Medicine, Evanston, Illinois 60201, USA.
Chen
Min
M
Weinstein
Lee S
LS
Jin
Jian-Ping
JP
D000595:Amino Acid Sequence; D000818:Animals; D004195:Disease Models, Animal; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics / Q000378:metabolism; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000235:genetics; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics; D013318:Stroke Volume / Q000235:genetics; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*; D024723:Ventricular Myosins / Q000235:genetics / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D019210:Troponin I; D024723:Ventricular Myosins; D019205:GTP-Binding Protein alpha Subunits, Gs