An Essential Role for ECSIT in Mitochondrial Complex I Assembly and Mitophagy in Macrophages

Abstract

Summary: ECSIT is a mitochondrial complex I (CI)-associated protein that has been shown to regulate the production of mitochondrial reactive oxygen species (mROS) following engagement of Toll-like receptors (TLRs). We have generated an Ecsit conditional knockout (CKO) mouse strain to study the in vivo role of ECSIT. ECSIT deletion results in profound alteration of macrophage metabolism, leading to a striking shift to reliance on glycolysis, complete disruption of CI activity, and loss of the CI holoenzyme and multiple subassemblies. An increase in constitutive mROS production in ECSIT-deleted macrophages prevents further TLR-induced mROS production. Surprisingly, ECSIT-deleted cells accumulate damaged mitochondria because of defective mitophagy. ECSIT associates with the mitophagy regulator PINK1 and exhibits Parkin-dependent ubiquitination. However, upon ECSIT deletion, we observed increased mitochondrial Parkin without the expected increase in mitophagy. Taken together, these results demonstrate a key role of ECSIT in CI function, mROS production, and mitophagy-dependent mitochondrial quality control. : Macrophages rely on fine-tuning their metabolism to fulfill their anti-bacterial functions. Carneiro et al. show that the complex I assembly factor ECSIT is an essential regulator of the balance between mitochondrial respiration and glycolysis and the maintenance of a healthy mitochondrial pool through mitophagy. Keywords: macrophages, complex I, mitophagy, glycolytic switch, ROS, mROS, oxidative stress