Cardiac Metabolic Pathways Affected in the Mouse Model of Barth Syndrome

Yan Huang,Satish K Madala,Enkhsaikhan Purevjav,Corey Powers,Arnold W Strauss,Jeffrey A Towbin,Sabzali Javadov,Wendy D Haffey,Zaza Khuchua,Kenneth D Greis,Cecilia Zazueta

doi:10.1371/journal.pone.0128561

Abstract

Cardiolipin (CL) is a mitochondrial phospholipid essential for electron transport chain (ETC) integrity. CL-deficiency in humans is caused by mutations in the tafazzin (Taz) gene and results in a multisystem pediatric disorder, Barth syndrome (BTHS). It has been reported that tafazzin deficiency destabilizes mitochondrial respiratory chain complexes and affects supercomplex assembly. The aim of this study was to investigate the impact of Taz-knockdown on the mitochondrial proteomic landscape and metabolic processes, such as stability of respiratory chain supercomplexes and their interactions with fatty acid oxidation enzymes in cardiac muscle. Proteomic analysis demonstrated reduction of several polypeptides of the mitochondrial respiratory chain, including Rieske and cytochrome c1 subunits of complex III, NADH dehydrogenase alpha subunit 5 of complex I and the catalytic core-forming subunit of F0F1-ATP synthase. Taz gene knockdown resulted in upregulation of enzymes of folate and amino acid metabolic pathways in heart mitochondria, demonstrating that Taz-deficiency causes substantive metabolic remodeling in cardiac muscle. Mitochondrial respiratory chain supercomplexes are destabilized in CL-depleted mitochondria from Taz knockdown hearts resulting in disruption of the interactions between ETC and the fatty acid oxidation enzymes, very long-chain acyl-CoA dehydrogenase and long-chain 3-hydroxyacyl-CoA dehydrogenase, potentially affecting the metabolic channeling of reducing equivalents between these two metabolic pathways. Mitochondria-bound myoglobin was significantly reduced in Taz-knockdown hearts, potentially disrupting intracellular oxygen delivery to the oxidative phosphorylation system. Our results identify the critical pathways affected by the Taz-deficiency in mitochondria and establish a future framework for development of therapeutic options for BTHS.

Highlights

Cardiolipin is a unique mitochondrial tetra-acyl phospholipid that has four fatty acyl chains
Mitochondria were isolated from ventricular myocardium of 2 wild type (WT) and 2 TazKD mice and subjected to 2D-DIGE analysis
We found nine polypeptides involved in oxidative phosphorylation, assembly of electron transport chain (ETC) complexes, and the ubiquinone biosynthesis pathway that were significantly decreased in TazKD

Summary

Introduction

Cardiolipin is a unique mitochondrial tetra-acyl phospholipid that has four fatty acyl chains. In most mammalian tissues the acyl-group composition is highly specific being predominantly comprised of 18-carbon unsaturated acyl chains, the vast majority of which are linoleic acid. L4CL-deficiency in humans results in the multisystem pediatric disorder known as Barth syndrome (BTHS) (OMIM: 302060). The causative BTHS gene, tafazzin (Taz), is located on the X-chromosome [3]. Taz is an evolutionarily conserved and ubiquitously expressed mitochondrial transacylase that is required for the final step of CL biosynthesis, including remodeling and generation of L4CL species. Mutations in the Taz gene result in reduction of L4CL and accumulation of CL species with unusual acyl-group compositions with higher degrees of saturation [4, 5]

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