Yoneshiro, T. | Search bioRxiv

bioRxiv2021

Metabolic flexibility via mitochondrial BCAA carrier SLC25A44 is required for optimal fever

Importing necessary metabolites into the mitochondrial matrix is a crucial step of fuel choice during stress adaptation. Branched chain-amino acids (BCAA, Valine, Leucine, and Isoleucine) are essential for anabolic processes like protein synthesis, but they are also imported into the mitochondria for catabolic reactions. What controls the distinct subcellular BCAA utilization during stress adaptation is insufficiently understood. The present study reports the role of SLC25A44, a recently identified mitochondrial BCAA carrier (MBC), in the regulation of mitochondrial BCAA catabolism and adaptive response to fever. We found that mitochondrial BCAA oxidation in brown adipose tissue (BAT) is significantly enhanced during fever in response to the pyrogenic mediator prostaglandin E2 (PGE2) and psychological stress. Genetic deletion of MBC in a BAT-specific manner blunts mitochondrial BCAA oxidation and non-shivering thermogenesis following intracerebroventricular PGE2 administration. At a cellular level, MBC is required for mitochondrial BCAA deamination as well as the synthesis of mitochondrial amino acids and TCA intermediates. Together, these results illuminate the role of MBC as a determinant of metabolic flexibility to mitochondrial BCAA catabolism and optimal febrile responses. This study also offers an opportunity to control fever by rewiring the subcellular BCAA fate.

cell biology↗

bioRxiv2019

Loss of a novel striated muscle-enriched mitochondrial protein Coq10a enhances postnatal cardiac hypertrophic growth

Postnatal mammalian cardiomyocytes undergo a major transition from hyperplasia (increases in cell numbers) to hypertrophy (expansion in cell size). This process is accompanied by rapid mitochondrial biogenesis and metabolic switches to meet the demand of increased cardiac output. Although most mitochondrial components express ubiquitously, recent transcriptomic and proteomic analyses have discovered numerous tissue-specific mitochondrial proteins whose physiological functions are largely unknown. Here we report that a highly evolutionarily conserved mitochondrial protein Coq10a is predominantly expressed in mammalian cardiac and skeletal muscles, and is highly up-regulated around birth in a thyroid hormone-dependent manner. Deletion of Coq10a by CRISPR/Cas9 leads to enhanced cardiac growth after birth. Surprisingly, adult Coq10a mutant mice maintain the hypertrophic heart phenotype with increased levels of coenzyme Q (CoQ) per cardiomyocyte, preserved cardiac contractile function and mitochondrial respiration, which contrasts with reported mice and humans with mutations in other Coq family genes. Further RNA-seq analysis and mitochondrial characterization suggest an increase of mitochondrial biogenesis in the Coq10a mutant heart as a possible consequence of Peroxisome proliferator-activated receptor Gamma Coactivator 1-alpha (PGC1) activation, consistent with a recent intriguing report that CoQ may function as a natural ligand and partial agonist of Peroxisome Proliferator-Activated Receptor (PPAR) /{gamma}. Taken together, our study reveals a previously unknown function of a novel striated muscle-enriched mitochondrial protein Coq10a in regulating postnatal heart growth.

developmental biology↗