MCART1 is required for mitochondrial NAD transport

Abstract

The nicotinamide adenine dinucleotide (NAD+/NADH) pair is a cofactor in redox reactions and is particularly critical in mitochondria as it connects substrate oxidation by the tricarboxylic acid (TCA) cycle to ATP generation by the electron transport chain (ETC) and oxidative phosphorylation. While a mitochondrial NAD+ transporter has been identified in yeast, how NAD enters mitochondria in higher eukaryotes is unknown. Here, we mine gene essentiality data from human cell lines to identify MCART1 (SLC25A51) as co-essential with ETC components. MCART1-null cells have large decreases in TCA cycle flux, mitochondrial respiration, ETC complex I activity, and mitochondrial levels of NAD+ and NADH. Isolated mitochondria from cells lacking or overexpressing MCART1 have greatly decreased or increased NAD uptake in vitro, respectively. Moreover, MCART1 and NDT1, a yeast mitochondrial NAD+ transporter, can functionally complement for each other. Thus, we propose that MCART1 is the long sought mitochondrial transporter for NAD in human cells.

Mitochondria in Neuronal Health: From Energy Metabolism to Parkinson's Disease

“…In the cytosol, NAD + is also an essential electron acceptor for glycolytic ATP production. Although the mitochondrial and cytosolic NAD + /NADH pools are separate, they are connected through multiple exchange routes, such as via the mitochondrial protein SLC25A51, a recently identified NAD + transporter, [ 29,30 ] and two shuttle systems in the mitochondrial inner membrane (the malate‐aspartate shuttle and the glycerol‐3‐phosphate shuttle) that replenish NAD + in the cytosol and transfer NADH to the mitochondrial matrix. [ 31 ] However, it is still unknown whether other NAD + precursors can be transported through the mitochondrial membrane to fuel its synthesis.…”

“…[ 218,219 ] The recent identification of the mitochondrial NAD + transporter now provides experimental access to dissect the molecular mechanisms influencing mitochondrial NAD + import and its role in axonal degeneration in neurodegenerative disease. [ 29,30 ]…”

Knocking out central metabolism genes to identify new targets and alternating substrates to improve lipid synthesis in Y. lipolytica

“…However, in the CSM-acetate medium, the cell growth of po1fk_ylPYC1 was repressed, suggesting that the deficiency of pyruvate carboxylase PYC1 would lead to the disruption of gluconeogenesis. Moreover, it is reported that the distributions of the cellular reducing equivalent are highly compartmentalized in eukaryotes, which is attributed to the specific localization of metabolic pathways and impermeabilities of organelles membranes (Kory et al, 2020). Specifically, mitochondria are important organelles for the NADH metabolism due to its respiratory functions, the existence of electron transport chain for oxidative phosphorylation.…”

Using mass spectrometry imaging to visualize age-related subcellular disruption

“…In addition, NAD + precursor supplementation improves mitochondrial function in aged mice and C. elegans (Gomes et al, 2013;Mouchiroud et al, 2013;Zhang et al, 2016), and overexpression of Nmnat3, an enzyme of the NAD + salvage pathway, restores TCA cycle capacity and suppresses mitochondrial ROS generation in skeletal muscle of aged mice (Maryam Gulshan et al, 2018). However, only recently, SLC25A51 was identified as the mitochondrial NAD + transporter (Girardi et al, 2020;Kory et al, 2020;Luongo et al, 2020), but little is known about the kinetics and regulation of NAD + and NAD + precursor influx into mitochondria in a physiological context and during aging. Flux analysis reveals incomplete equilibration of NAD + between cytosol and mitochondria (McReynolds et al, 2021), suggesting that this organelle can be particularly sensitive to disturbances in cellular NAD + levels.…”