The TIM22 complex regulates mitochondrial one-carbon metabolism by mediating the import of Sideroflexins

AbstractThe Acylglycerol Kinase (AGK) is a mitochondrial lipid kinase that contributes to protein biogenesis as a subunit of the TIM22 complex at the inner mitochondrial membrane. Mutations in AGK cause Sengers syndrome, an autosomal recessive condition characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. We undertook proteomic profiling of Sengers patient fibroblasts and an AGKKO cell line to map the proteomic changes that ensue upon AGK dysfunction. This uncovered extensive remodelling of mitochondrial one-carbon metabolism enzymes and showed that inner membrane serine transporters, Sideroflexins (SFXNs), are novel substrates of the TIM22 complex. Deletion of SFXN1 recapitulates the remodelling of one-carbon metabolism observed in Sengers patient cells. Proliferation of cells lacking AGK is perturbed in the absence of exogenous serine and rescuable through addition of formate, highlighting the dysregulation of one carbon metabolism as a key molecular feature in the biology of Sengers syndrome.

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The TIM22 complex mediates the import of Sideroflexins and is required for efficient mitochondrial one-carbon metabolism

Molecular Biology of the Cell ◽

10.1091/mbc.e20-06-0390 ◽

2021 ◽

pp. mbc.E20-06-0390

Author(s):

Thomas D. Jackson ◽

Daniella H. Hock ◽

Kenji M. Fujihara ◽

Catherine S. Palmer ◽

Ann E. Frazier ◽

...

Keyword(s):

Carbon Metabolism ◽

Mitochondrial Membrane ◽

Inner Mitochondrial Membrane ◽

Molecular Feature ◽

Lipid Kinase ◽

Skeletal Myopathy ◽

A Subunit ◽

Sengers Syndrome ◽

Mitochondrial Lipid ◽

One Carbon Metabolism

Acylglycerol Kinase (AGK) is a mitochondrial lipid kinase that contributes to protein biogenesis as a subunit of the TIM22 complex at the inner mitochondrial membrane. Mutations in AGK cause Sengers syndrome, an autosomal recessive condition characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. We mapped the proteomic changes in Sengers patient fibroblasts and AGKKO cell lines to understand the effects of AGK dysfunction on mitochondria. This uncovered downregulation of a number of proteins at the inner mitochondrial membrane, including many SLC25 carrier family proteins, which are predicted substrates of the complex. We also observed downregulation of SFXN proteins, which contain five transmembrane domains, and show that they represent a novel class of TIM22 complex substrate. Perturbed biogenesis of SFXN proteins in cells lacking AGK reduces the proliferative capabilities of these cells in the absence of exogenous serine, suggesting that dysregulation of one carbon metabolism is a molecular feature in the biology of Sengers syndrome.

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Hepatic Cystathionine β-Synthase Activity is Increased by Greater Post-ruminal Supply of Methionine During the Periparturient Period in Dairy Cows

Current Developments in Nutrition ◽

10.1093/cdn/nzz128 ◽

2019 ◽

Cited By ~ 1

Author(s):

Mario Vailati-Riboni ◽

Fernanda Batistel ◽

Rainie R C S Yambao ◽

Claudia Parys ◽

Yuan-Xiang Pan ◽

...

Keyword(s):

Energy Metabolism ◽

Dairy Cows ◽

Carbon Metabolism ◽

Production Efficiency ◽

Fumarate Hydratase ◽

Mrna Abundance ◽

Periparturient Period ◽

Inflammatory Status ◽

Metabolism Enzymes ◽

One Carbon Metabolism

Abstract Background Post-ruminal supply of Met during the periparturient period enhances production efficiency (feed conversion to milk) in dairy cows partly through alleviation of oxidant and inflammatory status. Whether alterations in hepatic one-carbon (major contributor of antioxidants) and/or energy-metabolism contribute to these beneficial effects is unknown. Objectives Investigate alterations in hepatic one-carbon and energy metabolism and associations with plasma amino acids (AA) and production efficiency in response to enhanced post-ruminal supply of Met. Methods Holstein cows (n = 30/group) were fed during the last 28 days of pregnancy a control diet (CON) or the control plus ethyl-cellulose rumen-protected methionine (MET; 0.9 g·kg−1 of dry matter intake). Plasma (n = 15/group) and liver tissue (n = 10/group) were collected throughout the periparturient period to evaluate AA profiles, activity of TCA cycle, and one-carbon metabolism via mRNA abundance, enzyme activity, and targeted metabolomics. Results Cows in MET had greater overall (27%, P = 0.027) plasma Met concentrations, but had similar total plasma AA concentrations. Although mRNA abundance of one-carbon metabolism enzymes did not differ, hepatic activity of cystathionine β-synthase (CBS) (51.2 vs. 44.4 mmol·h−1·mg−1 protein; P = 0.032) and concentration (19%, P = 0.048) of the cellular antioxidant glutathione were greater overall in MET. mRNA abundance of aconitase 2 and fumarate hydratase was greater overall (P = 0.049), and phosphoenolpyruvate carboxykinase 1 tended (P = 0.093) to be greater overall in cows fed MET. There was a tendency (P ≤ 0.093) for greater overall hepatic concentrations of malic acid, α-ketoglutaric acid, and isocitric acid in cows fed MET. Conclusions Greater activity of CBS in response to enhanced post-ruminal supply of Met likely contributes to alleviating oxidant status by increasing concentrations of glutathione. Hence, transsulfuration plays an important role in the observed improvements in production efficiency of dairy cows during the periparturient period.

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SFXN1 is a mitochondrial serine transporter required for one-carbon metabolism

Science ◽

10.1126/science.aat9528 ◽

2018 ◽

Vol 362 (6416) ◽

pp. eaat9528 ◽

Cited By ~ 50

Author(s):

Nora Kory ◽

Gregory A. Wyant ◽

Gyan Prakash ◽

Jelmi uit de Bos ◽

Francesca Bottanelli ◽

...

Keyword(s):

Carbon Metabolism ◽

Mitochondrial Membrane ◽

Mitochondrial Pathway ◽

Genetic Screen ◽

Inner Mitochondrial Membrane ◽

Unknown Mechanism ◽

One Carbon Metabolism ◽

The One ◽

Mitochondrial Membrane Protein

One-carbon metabolism generates the one-carbon units required to synthesize many critical metabolites, including nucleotides. The pathway has cytosolic and mitochondrial branches, and a key step is the entry, through an unknown mechanism, of serine into mitochondria, where it is converted into glycine and formate. In a CRISPR-based genetic screen in human cells for genes of the mitochondrial pathway, we found sideroflexin 1 (SFXN1), a multipass inner mitochondrial membrane protein of unclear function. Like cells missing mitochondrial components of one-carbon metabolism, those null for SFXN1 are defective in glycine and purine synthesis. Cells lacking SFXN1 and one of its four homologs, SFXN3, have more severe defects, including being auxotrophic for glycine. Purified SFXN1 transports serine in vitro. Thus, SFXN1 functions as a mitochondrial serine transporter in one-carbon metabolism.

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Development of a Standardized MRM Method for the Quantification of One Carbon Metabolism Enzymes

Methods in Molecular Biology - Clinical Proteomics ◽

10.1007/978-1-0716-1936-0_13 ◽

2021 ◽

pp. 159-175

Author(s):

Laura Guerrero ◽

Alberto Paradela ◽

Fernando J. Corrales

Keyword(s):

Carbon Metabolism ◽

Metabolism Enzymes ◽

One Carbon Metabolism

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The mitochondrial carrier SFXN1 is critical for Complex III integrity and cellular metabolism

10.1101/2020.06.18.157495 ◽

2020 ◽

Cited By ~ 1

Author(s):

Michelle Grace Acoba ◽

Ebru S. Selen Alpergin ◽

Santosh Renuse ◽

Lucía Fernández-del-Río ◽

Ya-Wen Lu ◽

...

Keyword(s):

Carbon Metabolism ◽

Coenzyme Q ◽

Integral Membrane Protein ◽

Central Carbon Metabolism ◽

Complex Iii ◽

Metabolic Efficiency ◽

Primary Role ◽

Inner Mitochondrial Membrane ◽

Mitochondrial Carrier ◽

One Carbon Metabolism

SUMMARYMitochondrial carriers (MC) mediate the passage of small molecules across the inner mitochondrial membrane (IMM) enabling regulated crosstalk between compartmentalized reactions. Despite MCs representing the largest family of solute carriers in mammals, most have not been subjected to a comprehensive investigation, limiting our understanding of their metabolic contributions. Here, we functionally characterized SFXN1, a member of the non-canonical, sideroflexin MC family. We find that SFXN1, an integral membrane protein in the IMM with an uneven number of transmembrane domains, is a novel TIM22 substrate. SFXN1 deficiency specifically impairs Complex III (CIII) biogenesis, activity, and assembly, compromising coenzyme Q levels. This CIII dysfunction is independent of one-carbon metabolism, the known primary role for SFXN1 as a mitochondrial serine transporter. Instead, SFXN1 supports CIII function by participating in heme and central carbon metabolism. Our findings highlight the multiple ways that SFXN1-based amino acid transport impacts mitochondrial and cellular metabolic efficiency.

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Quantitative proteomics of heavy metal exposure in Arabidopsis thaliana reveals alterations in one-carbon metabolism enzymes upon exposure to zinc

Journal of Proteomics ◽

10.1016/j.jprot.2014.03.006 ◽

2014 ◽

Vol 111 ◽

pp. 128-138 ◽

Cited By ~ 10

Author(s):

Bronwyn J. Barkla ◽

Rosario Vera-Estrella ◽

María Cristina Miranda-Vergara ◽

Omar Pantoja

Keyword(s):

Heavy Metal ◽

Arabidopsis Thaliana ◽

Carbon Metabolism ◽

Quantitative Proteomics ◽

Metal Exposure ◽

Heavy Metal Exposure ◽

Metabolism Enzymes ◽

One Carbon Metabolism

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Genetic Variation: Impact on Folate (and Choline) Bioefficacy

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000040 ◽

2010 ◽

Vol 80 (45) ◽

pp. 319-329 ◽

Cited By ~ 9

Author(s):

Allyson A. West ◽

Marie A. Caudill

Keyword(s):

Carbon Metabolism ◽

Genetic Variants ◽

Plasma Homocysteine ◽

Water Soluble ◽

Gene Interactions ◽

Dietary Folate ◽

Methyl Donors ◽

Common Genetic Variants ◽

One Carbon Metabolism ◽

The Impact

Folate and choline are water-soluble micronutrients that serve as methyl donors in the conversion of homocysteine to methionine. Inadequacy of these nutrients can disturb one-carbon metabolism as evidenced by alterations in circulating folate and/or plasma homocysteine. Among common genetic variants that reside in genes regulating folate absorptive and metabolic processes, homozygosity for the MTHFR 677C > T variant has consistently been shown to have robust effects on status markers. This paper will review the impact of genetic variants in folate-metabolizing genes on folate and choline bioefficacy. Nutrient-gene and gene-gene interactions will be considered along with the need to account for these genetic variants when updating dietary folate and choline recommendations.

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