Changes in essential myosin light chain isoform expression provide a molecular basis for isometric force regulation in the failing human heart

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Item Type:	Article
Title:	Changes in essential myosin light chain isoform expression provide a molecular basis for isometric force regulation in the failing human heart
Creators Name:	Morano, I., Haedicke, K., Haase, H., Boehm, M., Erdmann, E. and Schaub, M.C.
Abstract:	We investigated the effects of the expression of myosin light chain (MLC) isoforms on the Ca2+ sensitivity of isometric force production of demembranated (skinned) fibers of papillary muscle from the left ventricle of three groups: patients with ischemic cardiomyopathy, patients with dilated cardiomyopathy (NYHA IV) and normal human hearts. Expression and phosphorylation of the phosphorylatable MLC isoforms (MLC-2) was equal within all three groups. However, 72% of the patients investigated in this study expressed the atrial essential MLC (ALC-1) in addition to the essential ventricular MLC (VLC-1) ranging between 2.4% and 10.3%. Using fibers from failing hearts, we observed a significant positive correlation between ALC-1 and Ca2+ sensitivity in that the higher the ALC-1 expression the higher the Ca2(+)-sensitivity: pCa50 (Ca2+ required for half-maximal force production) was 5.87 without ALC-1 and 6.08 with 10.3% ALC-1. Fibers from a normal heart (no ALC-1) revealed a pCa50 of 5.85. Isoform and phosphorylation patterns of tropomyosin and troponin I remained unchanged in the patients and normal hearts. Our results suggest that Ca2+ responsiveness and force development of the human heart is regulated by the expression of different MLC-1 isoforms.
Keywords:	Myosin Light Chains, Human Failing Heart, Cardiomyopathy, Calcium Sensitivity
Source:	Journal of Molecular and Cellular Cardiology
ISSN:	0022-2828
Publisher:	Elsevier
Volume:	29
Number:	4
Page Range:	1177-1187
Date:	April 1997
Official Publication:	https://doi.org/10.1006/jmcc.1996.0353
PubMed:	View item in PubMed

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