Functional Insights on the Human Adenine Nucleotide Translocator Interactome

Abstract

The adenine nucleotide translocator (ANT), by mediating the exchange of ADP for ATP across the inner mitochondrial membrane, lies at the core of oxidative phosphorylation (OXPHOS). Discrepancies in ANT expression and/or activity resulting to reduced energy metabolism are linked to a wide spectrum of pathologies, including lactic acidosis, progressive external opthalmoplegia, muscular dystrophy and cardiomyopathy. In yeast, the major isoform was modeled for a long time to exist in isolation, but was demonstrated to physically interact with respiratory supercomplexes (RSCs) exclusively in the context of the phospholipid cardiolipin (CL). OXPHOS in CL‐null yeast is remarkably decreased in optimal situations and completely eliminated under stressful conditions, pointing to the physiological significance of these protein‐protein associations. In this study, we determined that human ANTs also have the capacity to assemble into high molecular weight complexes. Additionally, we defined the interactome of two human ANT isoforms using an unbiased proteomics approach. Similar to the yeast orthologue, we saw RSCs and other solute carriers as binding partners, which was surprising given that the organization of yeast and mammalian ANTs is different, with Complex I missing in yeast. To probe the physiological relevance of the ANT‐RSC interaction, we deleted the major ANT isoform in HEK293, which unexpectedly only had a moderate effect on OXPHOS, indicating that the minimal levels of the other isoforms can still support respiratory capacity. As a reciprocal inquiry, we ablated OXPHOS function and found that ADP/ATP transport by ANTs is impaired. These results provide insights regarding the physiological relevance of evolutionarily conserved interactions of proteins important for mitochondrial function.Support or Funding InformationThis work was supported by the National Institutes of Health (R01HL108882) to S.M.C and pre‐doctoral fellowships from the American Heart Association (16PRE31140006 to M.G.A. and 12PRE11910004 to Y‐W.L.).