| 2012 |
mARC1 is a signal-anchored protein of the outer mitochondrial membrane with an N(in)-C(out) membrane orientation; the N-terminal transmembrane helix is sufficient for mitochondrial targeting, the N-terminal targeting signal acts as a supportive receptor, membrane integration is membrane-potential-independent but requires external ATP, and the protein assembles into high-oligomeric complexes. The C-terminal catalytic domain is exposed to the cytosol. |
Subcellular fractionation, protease protection assays, deletion/truncation constructs, live-cell imaging, mitochondrial import assays with ATP depletion and membrane-potential uncouplers |
The Journal of Biological Chemistry |
High |
23086957
|
| 2014 |
Human mARC1 catalyzes reduction of nitrite to nitric oxide (NO) through its molybdenum cofactor; this activity requires Cys-273 (molybdenum-coordinating residue) as the C273A mutation abolishes NO formation. Replacement of molybdenum with tungsten also abolishes NO formation. mARC1 generates NO from nitrite in an electron transfer chain with NADH, cytochrome b5, and NADH-dependent cytochrome b5 reductase, with rate increasing ~3-fold at pH 6.5 vs 7.5. |
In vitro nitrite reduction assay with recombinant protein; active-site mutagenesis (C273A); tungsten substitution of molybdenum; lentiviral mARC1 expression in HEK cells with NO detection; Km/Vmax determination |
The Journal of Biological Chemistry |
High |
24500710
|
| 2014 |
mARC1 functions as part of an N-reductive enzyme system together with cytochrome b5 type B and NADH cytochrome b5 reductase to reduce N-hydroxylated compounds (benzamidoxime). SNP variants in MARC1 encoding A165T showed no altered kinetic parameters in benzamidoxime N-reduction, while multiple simultaneous amino acid substitutions reduced N-reductive activity ~5-fold. |
Recombinant protein expression in E. coli; in vitro steady-state enzyme kinetics with benzamidoxime; molybdenum quantification by ICP-MS; pyrosequencing-based genotyping |
Drug Metabolism and Disposition |
Medium |
24423752
|
| 2018 |
Crystal structure of human mARC1 was solved at high resolution, revealing the coordination geometry of the molybdenum cofactor (Moco), identifying two key active-site residues that distinguish mARC paralogs, and demonstrating that mARC1 belongs to the MOSC domain superfamily. The structure defines the catalytic mechanism for reduction of N-oxygenated compounds and provides evidence for an evolutionary relationship to the xanthine oxidase superfamily. |
X-ray crystallography (high-resolution crystal structure); structural comparison with in silico domain predictions; functional interpretation of active-site architecture |
Proceedings of the National Academy of Sciences of the United States of America |
High |
30397129
|
| 2022 |
Crystal structure of the mARC1 p.A165T variant protein at near-atomic resolution shows that this clinically protective variant does not alter the overall protein fold or active-site architecture compared to wildtype mARC1. |
X-ray crystallography of variant protein; structural comparison to wildtype crystal structure |
Hepatology Communications |
Medium |
35560545
|
| 2023 |
Hepatocyte-specific mARC1 knockdown (via GalNAc-siRNA in a NASH mouse model) reduced hepatic triglyceride accumulation but increased plasma triglycerides; in primary human hepatocytes, mARC1 knockdown decreased lipid accumulation and increased triglyceride secretion. mARC1 knockdown also decreased secretion of 3-hydroxybutyrate (a β-oxidation marker) in vitro and in vivo, implicating mARC1 in hepatic lipid metabolism and ketogenesis. |
GalNAc-siRNA hepatocyte-specific knockdown in GAN-diet NASH mouse model; primary human hepatocyte in vitro model with siRNA KD; metabolic readouts (triglycerides, 3-hydroxybutyrate); RNA-sequencing pathway analysis |
JHEP Reports |
High |
37122688
|
| 2024 |
The protective MTARC1 p.A165T variant causes dramatically reduced protein stability of mARC1 (assessed by protein stability reporter system in multiple cell lines and in mouse liver), without altering mRNA levels. Multiple substitutions at position A165 (A165S, A165N, A165V, A165G, A165D) similarly reduced stability, indicating A165 is essential for mARC1 protein stability. |
Protein stability reporter system in multiple cell lines; murine knock-in model (A168T equivalent); Western blot; mutagenesis of A165 to multiple residues |
Biochemical and Biophysical Research Communications |
Medium |
38340654
|
| 2024 |
The protective p.A165T substitution causes protein instability and aberrant localization of mARC1 in hepatic cells. Novel rare putative loss-of-function MARC1 variants identified by exome-wide association study show a phenotype similar to p.A165T/p.M187K variants, consistent with loss-of-function being hepatoprotective. Marc1 knockout mice, unlike human carriers, do not show protection against hepatic triglyceride accumulation, revealing a divergent physiological role between human and mouse (attributed to Marc2 being the dominant paralog in mouse liver). |
Exome-wide association study (n=540,000); in vitro expression of recombinant human MARC1 A165T with localization studies in hepatic cells; Marc1 knockout mouse generation; liver phenotype assessment in KO mice on steatogenic diet |
PLoS Genetics |
Medium |
38437227
|
| 2024 |
Hepatocyte-specific Mtarc1 siRNA knockdown in ob/ob and diet-induced MASH mouse models reduced serum liver enzymes, LDL-cholesterol, liver triglycerides, liver weight, and attenuated liver pathological changes. Multi-omics (metabolomics, proteomics, lipidomics) analysis showed that Mtarc1 knockdown partially restored diet-altered metabolites and lipids. |
GalNAc-conjugated siRNA hepatocyte-specific knockdown in ob/ob and diet-induced MASH mouse models; multi-omics (metabolomics, proteomics, lipidomics); histology; serum biochemistry |
Hepatology Communications |
High |
38696369
|
| 2024 |
mARC1 siRNA knockdown in primary human hepatocytes reduced neutral lipid content specifically in cells homozygous for the risk allele (p.A165), and this reduction was mediated by increased fatty acid β-oxidation (measured by radiolabeled tracer). mARC1 knockdown also reduced ferroptosis and reactive oxygen species levels. In human UK Biobank participants, carriers of the rs2642438 minor allele had higher circulating 3-hydroxybutyrate levels, consistent with increased β-oxidation. |
siRNA knockdown in primary human hepatocytes; radiolabeled fatty acid oxidation assay; Oil-Red O staining; RNA-sequencing and LC-MS proteomics; UK Biobank metabolomics |
Clinical and Molecular Hepatology |
High |
39716370
|
| 2024 |
mARC1 is the main contributor to reductive biotransformation of N-hydroxyurea (NHU) to urea; in vitro and in vivo evidence establishes that this N-reductive activity is specifically mediated by mARC1 (not mARC2), suggesting mARC1-mediated inactivation as a pharmacological mechanism requiring high doses of hydroxyurea in therapy. |
In vitro N-reductive assay with recombinant mARC1 and mARC2; in vivo metabolic studies; substrate specificity determination |
Journal of Medicinal Chemistry |
Medium |
39397364
|
| 2024 |
mARC1 depletion improved cellular bioenergetics and decreased mitochondrial superoxide production in response to lipotoxic stress in cells. The p.A165T variant maintains mitochondrial localization despite lower protein levels. Global or hepatocyte-specific mARC1 deletion in mice reduced liver steatosis and fibrosis in multiple MASH and liver fibrosis models. RNA-seq showed downregulation of extracellular matrix remodeling and collagen formation pathways upon mARC1 loss. |
mARC1 knockdown/KO in cells with bioenergetics and mitochondrial superoxide assays; global and conditional KO mice on diet-induced MASH models; RNA-seq; plasma lipidomics; histology |
Hepatology Communications |
High |
39927988
|
| 2024 |
mARC1 modulates lipid accumulation in primary human hepatocytes and primary human adipocytes; mARC1 depletion affects accumulation of distinct lipid species and expression of inflammatory and mitochondrial pathway genes/proteins in both in vitro and in vivo models. Protective MTARC1 variants decrease protein accumulation in overexpression systems (without altering mRNA). A plasma lipid biomarker (Ceramide 22:1) predictive of mARC1 abundance was identified. |
siRNA knockdown and lentiviral overexpression in primary human hepatocytes, hepatocyte cell lines, and primary human adipocytes; in vivo murine MASH model with GalNAc-siRNA; lipidomics; proteomics; transcriptomics |
Hepatology Communications |
Medium |
38619429
|
| 2026 |
MTARC1 deficiency post-transcriptionally upregulates glycerophospholipid (GPL) biosynthetic enzymes CEPT1 and PEMT, leading to altered phospholipid composition in lipid droplets (LDs). This phospholipid remodeling reduces LD size, increases surface-to-volume ratio, and thereby enhances LD degradation via lipolysis and lipophagy. Knockdown of CEPT1 or PEMT reversed the hepatoprotective effects of MTARC1 deficiency, establishing an MTARC1-GPL biosynthesis-LD degradation axis. |
Global and liver-specific Mtarc1 KO mice; genetic inhibition of Pnpla2, Lipa, Pemt, Cept1; multi-omics (biochemical, histological, lipidomics, proteomics); in vitro cell culture mechanistic studies; LD size/number quantification |
Liver International |
High |
41641916
|
| 2026 |
MTARC1 knockdown in HCC cell lines (Hep3B2, HuH7, HepG2, HepaRG) reduced proliferation; CRISPR-Cas9 KO in Hep3B2 cells decreased neutral lipid accumulation, enhanced β-oxidation, and reduced cell migration. MTARC1 KO xenograft tumors showed reduced volume. Proteomics revealed inhibition of oncogenic pathways and activation of anti-proliferative proteins upon MTARC1 loss. |
siRNA knockdown in multiple HCC cell lines; CRISPR-Cas9 KO; lipid accumulation assay; β-oxidation assay; migration assay; subcutaneous xenograft mouse model; global proteomics |
Clinical and Molecular Hepatology |
Medium |
41644117
|
| 2026 |
Mtarc1 KO mice on choline-deficient high-fat diet showed reduced liver steatosis, pro-fibrosis markers, and inflammation. Primary hepatocytes from Mtarc1 KO mice exhibited reduced lipid droplet accumulation, decreased fatty acid uptake, and increased lipid secretion. Metabolomics showed hepatic enrichment of phospholipids in Mtarc1 KO mice. |
Mtarc1 KO mouse model; CDAHFD-induced MASLD model; primary hepatocyte isolation; lipid droplet imaging; fatty acid uptake assay; lipid secretion assay; untargeted metabolomics |
Liver International |
High |
41527487
|