Upregulation of cardiomyocyte ribonucleotide reductase increases intracellular 2 deoxy-ATP, contractility, and relaxation

Korte, F.S. and Dai, Jin and Buckley, Kate and Feest, Erik R. and Adamek, N. and Geeves, M.A. and Murry, Charles E. and Regnier, Michael (2011) Upregulation of cardiomyocyte ribonucleotide reductase increases intracellular 2 deoxy-ATP, contractility, and relaxation. Journal of Molecular and Cellular Cardiology, 51 (6). pp. 894-901. ISSN 0022-2828. (The full text of this publication is not available from this repository)

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Official URL
http://dx.doi.org/10.1016/j.yjmcc.2011.08.026

Abstract

We have previously demonstrated that substitution of ATP with 2 deoxy-ATP (dATP) increased the magnitude and rate of force production at all levels of Ca2+-mediated activation in demembranated cardiac muscle. In the current study we hypothesized that cellular [dATP] could be increased by viral-mediated overexpression of the ribonucleotide reductase (Rrm1 and Rrm2) complex, which would increase contractility of adult rat cardiomyocytes. Cell length and ratiometric (Fura2) Ca2+ fluorescence were monitored by video microscopy. At 0.5 Hz stimulation, the extent of shortening was increased ~ 40% and maximal rate of shortening was increased ~ 80% in cardiomyocytes overexpressing Rrm1 + Rrm2 as compared to non-transduced cardiomyocytes. The maximal rate of relaxation was also increased ~ 150% with Rrm1 + Rrm2 overexpression, resulting in decreased time to 50% relaxation over non-transduced cardiomyocytes. These differences were even more dramatic when compared to cardiomyocytes expressing GFP-only. Interestingly, Rrm1 + Rrm2 overexpression had no effect on minimal or maximal intracellular [Ca2+], indicating increased contractility is primarily due to increased myofilament activity without altering Ca2+ release from the sarcoplasmic reticulum. Additionally, functional potentiation was maintained with Rrm1 + Rrm2 overexpression as stimulation frequency was increased (1 Hz and 2 Hz). HPLC analysis indicated cellular [dATP] was increased by approximately 10-fold following transduction, becoming ~ 1.5% of the adenine nucleotide pool. Furthermore, 2% dATP was sufficient to significantly increase crossbridge binding and contractile force during sub-maximal Ca2+ activation in demembranated cardiac muscle. These experiments demonstrate the feasibility of directly targeting the actin–myosin chemomechanical crossbridge cycle to enhance cardiac contractility and relaxation without affecting minimal or maximal Ca2+. This article is part of a Special issue entitled "Possible Editorial".

Item Type: Article
Uncontrolled keywords: ► dATP enhances myocardial contraction via increased crossbridge binding and kinetics. ► [dATP] can be increased > 10-fold via ribonucleotide reductase (Rrm) overxpression. ► Rrm overexpression increased intact cardiomyocyte contractility and relaxation. ► Rrm overexpression had no effect on Ca2+ transient magnitude. ► Myofilament targeted gene manipulations can improve cardiac function.
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 27 Mar 2012 15:47
Last Modified: 17 Apr 2012 13:19
Resource URI: http://kar.kent.ac.uk/id/eprint/29217 (The current URI for this page, for reference purposes)
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