Biology subjects

Pena, I. A.

Publications and source records attributed to Pena, I. A..

3 recordsLinked to original sources

bioRxiv2025

Sideroflexins enable mitochondrial transport of polar neutral amino acids

Mitochondria contribute to compartmentalized metabolism in eukaryotic cells, supporting key enzymatic reactions for cell function and energy homeostasis. This compartmentalization necessitates regulated metabolite transport across mitochondrial membranes. While many transport proteins have been identified, several mitochondrial transporters remain poorly characterized. Among these are sideroflexins, an evolutionarily conserved family of mitochondrial inner membrane proteins with unclear function. Using CRISPR/Cas9-mediated candidate transporter knockouts coupled with assessment of mitochondrial membrane permeability via a swelling assay, we identify SFXN1, previously implicated in mitochondrial serine transport and iron homeostasis, as an enabler of mitochondrial transport of multiple neutral amino acids, including proline, glycine, threonine, taurine, hypotaurine, {beta}-alanine, and {gamma}-aminobutyric acid (GABA). We further show that SFXN paralogues exhibit substrate-dependent functional overlap, with SFXN2 and SFXN3 partially rescuing loss of SFXN1 function in glycine-related phenotypes, while SFXN2 and SFXN5 partially rescue SFXN1-dependent changes in enabling GABA transport and metabolism. Altogether, these data establish sideroflexins as key regulators of mitochondrial amino acid transport and metabolism.

biochemistry↗

bioRxiv2020

MCART1 is required for mitochondrial NAD transport

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.

cell biology↗

bioRxiv2018

LARP1 is a major phosphorylation substrate of mTORC1

The mammalian target of rapamycin complex 1 (mTORC1) controls critical cellular functions such as protein synthesis, lipid metabolism, protein turnover and ribosome biogenesis through the phosphorylation of multiple substrates. In this study, we examined the phosphorylation of a recently identified target of mTORC1: La-related protein 1 (LARP1), a member of the LARP superfamily. Previously, we and others have shown that LARP1 plays an important role in repressing TOP mRNA translation downstream of mTORC1. LARP1 binds the 7-methylguanosine triphosphate (m7Gppp) cap moiety and the adjacent 5terminal oligopyrimidine (5TOP) motif of TOP mRNAs, thus impeding the assembly of the eIF4F complex on these transcripts. mTORC1 plays a critical role in the control of TOP mRNA translation via LARP1 but the precise mechanism by which this occurs is incompletely understood. The data described herein help to elucidate this process. Specifically, it show that: (i) mTORC1 interacts with LARP1, but not other LARP superfamily members, via the C-terminal region that comprises the DM15 domain, (ii) mTORC1 pathway controls the phosphorylation of multiple (up to 26) serine and threonine residues on LARP1 in vivo, (iii) mTORC1 regulates the binding of LARP1 to TOP mRNAs and (iv) phosphorylation of S689 by mTORC1 is particularly important for the association of the DM15 domain of LARP1 with the 5UTR of RPS6 TOP mRNA. These data reveal LARP1 as a major substrate of mTORC1.

biochemistry↗