Cardiac mitochondrial proteome dynamics with heavy water reveals stable rate of mitochondrial protein synthesis in heart failure despite decline in mitochondrial oxidative capacity

Abstract

We recently developed a method to measure mitochondrial proteome dynamics with heavy water (2H2O)-based metabolic labeling and high resolution mass spectrometry. We reported the half-lives and synthesis rates of several proteins in the two cardiac mitochondrial subpopulations, subsarcolemmal and interfibrillar (SSM and IFM), in Sprague Dawley rats. In the present study, we tested the hypothesis that the mitochondrial protein synthesis rate is reduced in heart failure, with possible differential changes in SSM versus IFM. Six to seven week old male Sprague Dawley rats underwent transverse aortic constriction (TAC) and developed moderate heart failure after 22 weeks. Heart failure and sham rats of the same age received heavy water (5% in drinking water) for up to 80 days. Cardiac SSM and IFM were isolated from both groups and the proteins were separated by 1D gel electrophoresis. Heart failure reduced protein content and increased the turnover rate of several proteins involved in fatty acid oxidation, electron transport chain and ATP synthesis, while it decreased the turnover of other proteins, including pyruvate dehydrogenase subunit in IFM, but not in SSM. Because of these bidirectional changes, the average overall half-life of proteins was not altered by heart failure in both SSM and IFM. The kinetic measurements of individual mitochondrial proteins presented in this study may contribute to a better understanding of the mechanisms responsible for mitochondrial alterations in the failing heart.

Assessing Cardiac Metabolism

“…Recent work has also shown the utility of 2 H 2 O for assessment of mitochondrial proteome dynamics. 172 The field is likely to grow.…”

Solving mitochondrial mysteries

“…Chan et al [23] detail their elegant methods for measuring turnover rate of mitochondrial proteins and show that mitochondrial proteins turn over at different rates. A recent paper by Shekar et al [24] also obtained a similar finding. If mitophagy was the main mechanism of mitochondrial protein turnover, one would expect that all mitochondrial proteins would have a similar turnover rate.…”

Sex differences in the regulation of spatially distinct cardiac mitochondrial subpopulations

“…Palmitoylcarnitine oxidation reflects mitochondrial palmitoylcarnitine transport, palmitate oxidation, the activity of entire ETC, and the phosphorylation process. The combination of glutamate and malate as substrate produces NADH, source of electron for Complex I, thus allowing the study of the malate-aspartate shuttle [30]. In the heart, the malate-aspartate shuttle is the dominant pathway with the rate of transporting NADH into mitochondria 10-fold than NADH delivery via a-glycerophosphate shuttle [31].…”