MOTS-c (mitochondrial open reading frame of the 12S rRNA-c) is a 16-amino-acid mitochondrial-derived peptide encoded by a 51-bp alternative ORF inside the mitochondrial 12S rRNA gene (MT-RNR1); because the mitochondrial genetic code reads the ORF as tandem start and stop codons, the peptide must be translated in the cytosol from an exported mitochondrial transcript, and nuclear NUMT copies of the locus do not encode the exact peptide. The peptide is amphipathic and cationic, with a hydrophobic core (Tyr8-Tyr11) and a basic C-terminal tail (Arg13-Arg16) that together govern both its nuclear entry and its interaction with nucleic acids and bacterial membranes. It is detected in mitochondria, in the nucleus and in extracellular fluid, circulating in human and rodent plasma; muscle and plasma levels rise with exercise and change with age. In the nucleus, following glucose restriction or oxidative stress, it occupies antioxidant response element (ARE)-containing promoters and associates with the ARE-regulating transcription factors NFE2L2/NRF2, NFE2L1/NRF1 and ATF1, thereby modulating RNA polymerase II-dependent stress-response gene expression - a case of a mitochondrially encoded factor acting on the nuclear genome. Applied as synthetic peptide it inhibits the folate-methionine cycle and de novo purine biosynthesis, causing AICAR to accumulate and AMPK to be activated, with downstream effects on glucose utilisation, insulin sensitivity, adiposity and muscle wasting signalling in rodents. As a cationic amphipathic peptide it also aggregates and damages Escherichia coli and methicillin-resistant Staphylococcus aureus directly, is induced in human monocytes by interferon gamma and lipopolysaccharide, and protects mice from MRSA challenge, properties shared with classical host defence peptides. The common Asian mtDNA variant m.1382A>C substitutes Lys14 with Gln and reduces the peptide's insulin-sensitising activity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0001649 osteoblast differentiation | IDA PMID:30468456 MOTS-c improves osteoporosis by promoting osteogenic differe... | MARK AS OVER ANNOTATED | Summary: Synthetic MOTS-c added to cultured rat bone-marrow mesenchymal stem cells increased osteogenic markers and calcified-nodule formation, an effect reversed by TGF-beta1 knockdown. This is pharmacology on rat cells rather than evidence that endogenous human MOTS-c participates in osteoblast differentiation. Reason: The experiment applies exogenous peptide to rat BMSCs and reads out differentiation markers; no endogenous MOTS-c manipulation, no human cells and no molecular target in the TGF-beta/SMAD pathway are shown. The peptide is not reported to catalyse or structurally contribute to any step of osteoblast differentiation, so involved_in overstates what was observed. Retained rather than removed because the observation itself is a direct assay and may reflect a real, if indirect, response to the peptide. Supporting Evidence: PMID:30468456 Rat BMSCs were isolated and cultured, followed by osteogenic and lipid differentiation. PMID:30468456 MOTS-c treatment could remarkably stimulate the formation of calcified nodules in BMSCs. |
| GO:0003677 DNA binding | IDA PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: Electrophoretic mobility shift assays showed concentration-dependent binding of synthetic MOTS-c to ARE-containing promoter fragments of several NRF2 target genes, and ChIP-qPCR showed stress-induced occupancy of the HO-1 and NQO1 promoters in cells. This is the best-supported molecular activity of the peptide. Reason: Direct in vitro DNA binding plus in-cell chromatin occupancy. GO:0003677 is the right level of specificity. Although the probes carried ARE motifs, the specificity controls were alanine substitutions of the hydrophobic core and the cationic tail, which also remove the residues that would drive non-specific peptide-nucleic acid binding, so sequence specificity (GO:0043565, GO:0000976) is not established and should not be asserted. Supporting Evidence: PMID:29983246 we found that MOTS-c directly bound DNA sequences of ARE-containing promoter regions of NRF2 target genes, including HO-1, NQO1, UGT1A1, UGT1A6, TXN, FTL, and GPX2, in a concentration-dependent manner PMID:29983246 The binding of MOTS-c to promoter regions of HO-1 and NQO1 containing ARE sites significantly increased 3 hr after being challenged with GR and tBHP |
| GO:0005515 protein binding | IPI PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | REMOVE | Summary: Bare protein-binding row recording the NFE2L2/NRF2 co-immunoprecipitation from the same paper that supports the informative GO:0140297 row against the same partner. Reason: Per curation policy, GO:0005515 conveys no functional information. The same interaction with the same partner (Q16236, NFE2L2) is already captured by GO:0140297 DNA-binding transcription factor binding from the same reference, which states what kind of partner it is; this row is redundant. Supporting Evidence: PMID:29983246 NRF2 co-immunoprecipitated with MOTS-c only from nuclear extracts of cells treated with GR and tBHP for 3 hr |
| GO:0005576 extracellular region | IDA PMID:25738459 The mitochondrial-derived peptide MOTS-c promotes metabolic ... | ACCEPT | Summary: Endogenous MOTS-c was measured in human and rodent plasma with a peptide-specific ELISA, and circulating levels respond to fasting and exercise. The peptide behaves as a secreted, circulating factor. Reason: Detection of the endogenous peptide in plasma, in two species, with independent corroboration of exercise-induced and age-dependent changes in circulating levels. This is the location claim that rests least on exogenous peptide. Supporting Evidence: PMID:25738459 as well as in circulation in human and rodent plasma as determined with a MOTS-c specific ELISA PMID:33473109 ELISA revealed that relative levels of circulating endogenous MOTS-c also significantly increased during (1.6-fold) and after (1.5-fold) exercise |
| GO:0005576 extracellular region | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0243 Secreted), itself derived from the plasma ELISA data of Lee et al. 2015. Reason: The mapping is correct and concordant with the IDA row from the same underlying evidence. Supporting Evidence: PMID:25738459 as well as in circulation in human and rodent plasma as determined with a MOTS-c specific ELISA |
| GO:0005634 nucleus | EXP PMID:33473109 MOTS-c is an exercise-induced mitochondrial-encoded regulato... | ACCEPT | Summary: Fluorescently labelled MOTS-c applied to C2C12 myoblasts entered the nucleus in a time-dependent manner, confirming the earlier report of a nuclear pool. Reason: Concordant with the stronger endogenous-peptide nuclear evidence of PMID:29983246. On its own this experiment tracks only exogenous FITC-labelled peptide and would be weak, but as corroboration of an independently established nuclear pool it is sound. Supporting Evidence: PMID:33473109 Using fluorescently labeled MOTS-c peptide (MOTS-c-FITC), we confirmed that exogenously treated MOTS-c also dynamically translocated to the nucleus in a time-dependent manner |
| GO:0005634 nucleus | IDA PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: Endogenous MOTS-c was detected in the nucleus by immunofluorescence and by immunoblotting of nuclear extracts, at low levels at rest and strongly increased 3 h after glucose restriction or oxidative stress; nuclear entry requires the hydrophobic core (Tyr8-Tyr11). Reason: Direct localisation of the endogenous peptide with a stress-dependent increase and a sequence requirement, supported by functional consequences in the nucleus (ARE promoter occupancy, transcription-factor association). This is a core location. Supporting Evidence: PMID:29983246 low levels of endogenous MOTS-c were detected in the nucleus under resting conditions by immunofluorescence microscopy PMID:29983246 to alanines (8YIFY11 to 8AAAA11) prevented EGFP-MOTS-c from entering the nucleus |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping (SL-0191 Nucleus), derived from the nuclear localisation data of Kim et al. 2018 and Reynolds et al. 2021. Reason: The mapping is correct and concordant with the IDA and EXP rows from the same underlying evidence. Supporting Evidence: PMID:29983246 low levels of endogenous MOTS-c were detected in the nucleus under resting conditions by immunofluorescence microscopy |
| GO:0005739 mitochondrion | IDA PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | KEEP AS NON CORE | Summary: Under resting conditions endogenous MOTS-c is mostly extra-nuclear with partial mitochondrial association, consistent with the partial mitochondrial co-localisation reported in the original characterisation. Reason: Direct imaging of the endogenous peptide in two independent papers, and loss of signal on mtDNA (rho-zero) or mitochondrial RNA (actinonin) depletion ties the peptide to the organelle. Note that the association is partial rather than exclusive, which is expected for a peptide that must be translated in the cytosol. ORGANELLES check (2026-11-03). Immunofluorescence co-localisation is an organelle-level assay that cannot resolve a sub-compartment, and the record has no transit peptide or transmembrane segment, so the row stays at the root with no sub-compartment added. The action moves from ACCEPT to KEEP_AS_NON_CORE because none of the peptide's characterised activities (nuclear ARE-promoter binding, secreted antimicrobial action) is shown in the organelle, and core_functions name nucleus and extracellular region only; the mitochondrial pool is a real but peripheral location. Supporting Evidence: PMID:29983246 endogenous MOTS-c exhibited a predominantly extra-nuclear localization pattern with a certain degree of mitochondrial association PMID:25738459 HeLa and HEK293 cells showed a certain degree of mitochondrial co-localization |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt subcellular-location mapping (SL-0173 Mitochondrion), derived from the co-localisation data of Lee et al. 2015 and Kim et al. 2018. Reason: The mapping is correct and concordant with the IDA row from the same underlying evidence. ORGANELLES check (2026-11-03), examined as a synthesis row. GO_REF:0000044 maps SL-0173, which rests on UniProt's curated location tied to Kim et al. 2018 (ECO:0000269), so the organelle claim holds; the source itself is organelle-level imaging, so nothing finer was lost in the mapping. Moved from ACCEPT to KEEP_AS_NON_CORE to match the IDA row: the mitochondrial pool is real but no core activity is shown there. Supporting Evidence: file:human/MT-RNR1__A0A0C5B5G6/MT-RNR1__A0A0C5B5G6-uniprot.txt Mitochondrion {ECO:0000269|PubMed:29983246} PMID:25738459 HeLa and HEK293 cells showed a certain degree of mitochondrial co-localization |
| GO:0006357 regulation of transcription by RNA polymerase II | IDA PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: In the nucleus after glucose restriction, MOTS-c occupies ARE-containing promoters, associates with ARE-regulating transcription factors, increases ARE-luciferase reporter activity and changes expression of several hundred nuclear genes that overlap with bona fide NRF2 targets. Reason: The peptide itself binds the promoter DNA and the transcription factors acting there, so it does part of the work of regulating polymerase II transcription rather than merely being required for it. This, together with the DNA- and transcription-factor-binding activities, is the core nuclear function and the most distinctive claim about the peptide (a mitochondrially encoded regulator of the nuclear genome). Supporting Evidence: PMID:29983246 we found that MOTS-c directly bound DNA sequences of ARE-containing promoter regions of NRF2 target genes, including HO-1, NQO1, UGT1A1, UGT1A6, TXN, FTL, and GPX2, in a concentration-dependent manner PMID:29983246 In the nucleus, MOTS-c regulated a broad range of genes in response to glucose restriction, including those with antioxidant response elements (ARE), and interacted with ARE-regulating stress-responsive transcription factors, such as nuclear factor erythroid 2-related factor 2 (NFE2L2/NRF2) |
| GO:0032147 activation of protein kinase activity | IDA PMID:25738459 The mitochondrial-derived peptide MOTS-c promotes metabolic ... | MODIFY | Summary: MOTS-c treatment increased AMPK alpha Thr172 phosphorylation, but the paper's own mechanism places two steps between peptide and kinase - inhibition of the folate cycle blocks de novo purine synthesis, AICAR accumulates more than 20-fold, and AICAR is the known AMPK activator. Reason: GO:0032147 means initiating the activity of an inactive protein kinase, which implies an action on the kinase. Here the proximate activator is the metabolite AICAR, and no direct MOTS-c target in the folate cycle has been identified; AMPK activation occurred despite lower AMP levels. A regulation-level term for a serine/threonine kinase states what was observed without claiming the peptide acts on the kinase. Proposed replacements: positive regulation of protein serine/threonine kinase activity Supporting Evidence: PMID:25738459 resulting in an accumulation of endogenous AICAR (5-aminoimidazole-4-carboxamide ribonucleotide) to levels higher than 20-fold in MOTS-c-ST cells compared to control cells PMID:25738459 MOTS-c treatment led to the phosphorylation of AMPKΞ± (Thr172) and Akt (Ser473) in a time and dose-dependent manner |
| GO:0033687 osteoblast proliferation | IDA PMID:31081069 MOTS-c improves osteoporosis by promoting the synthesis of t... | MARK AS OVER ANNOTATED | Summary: Synthetic MOTS-c increased CCK-8 viability signal and COL1A1/COL1A2 expression in the hFOB1.19 osteoblast line, with partial reversal by TGF-beta or SMAD7 knockdown. Reason: The readout is a CCK-8 viability assay after peptide addition at 0.5-1.0 micromolar, not a demonstration that endogenous MOTS-c participates in osteoblast proliferation; the paper's own emphasis is collagen synthesis. Retained rather than removed because the direct assay stands, but it should not be read as a process the peptide performs. Supporting Evidence: PMID:31081069 Cell viability was significantly increased after treatment of 1.0 ΞΌM MOTS-c for 24 h or 0.5 ΞΌM MOTS-c for 48 h in a time-dependent manner. |
| GO:0043610 regulation of carbohydrate utilization | IDA PMID:25738459 The mitochondrial-derived peptide MOTS-c promotes metabolic ... | KEEP AS NON CORE | Summary: MOTS-c-overexpressing and peptide-treated cells show increased glucose clearance, lactate accumulation and glycolytic flux, and treated mice show improved glucose tolerance and insulin sensitivity; the effects require AMPK and are reversed by folate. Reason: This is the headline physiological effect of the peptide and is supported by cellular flux measurements plus whole-animal glucose tolerance tests, so it should be kept. It is not a core molecular role, however - it is the distal output of the folate-AICAR-AMPK cascade, several steps downstream of any activity the peptide performs itself, and it was obtained with stable overexpression, exogenous peptide and daily injections rather than at endogenous levels. Supporting Evidence: PMID:25738459 MOTS-c appeared to stimulate glucose utilization evidenced by increased glucose clearance and lactate accumulation in culture media PMID:25738459 Its primary target organ appears to be the skeletal muscle, and its cellular actions inhibit the folate cycle and its tethered de novo purine biosynthesis, leading to AMPK activation. |
| GO:0048630 skeletal muscle tissue growth | IDA PMID:33554779 MOTS-c reduces myostatin and muscle atrophy signaling. | MARK AS OVER ANNOTATED | Summary: Injected MOTS-c reduced myostatin levels and muscle-atrophy signalling in high-fat-diet mice; the muscle-mass difference itself was apparent only after normalising to body weight. Reason: The authors state that absolute muscle masses did not differ between treatment groups and that the effect emerged only on body-weight adjustment in peptide-injected mice; the companion experiment is prevention of palmitate-induced atrophy, i.e. protection against loss rather than growth. Growth of skeletal muscle tissue is therefore not established, and in any case would be a distal consequence of the CK2-PTEN-AKT-FOXO1-myostatin cascade rather than a process the peptide carries out. Supporting Evidence: PMID:33554779 Although no differences were found between any of the three treatment groups when considering total, gastrocnemius, soleus, and plantaris absolute muscle mass, differences were more visible when performing an adjustment calculation with body weight. PMID:33554779 We administered MOTS-c (0.5 mg/kg/day, ip injection) in HFD (60 kcal% fat)-fed mice for 3 wk and examined gastrocnemius, soleus, and plantaris muscle mass. |
| GO:0071902 positive regulation of protein serine/threonine kinase activity | IDA PMID:33554779 MOTS-c reduces myostatin and muscle atrophy signaling. | KEEP AS NON CORE | Summary: MOTS-c treatment increased AKT Ser473 phosphorylation (an mTORC2-dependent site) in skeletal muscle of diet-induced obese mice, while Thr308 was unchanged, and increased CK2 substrate phosphorylation. Reason: A regulation-level term is appropriate for an indirect effect, and the phospho-site specificity (Ser473 but not Thr308) argues the effect is real rather than a generic signalling shift. It is not a core function - the peptide acts through a multi-step cascade (CK2, PTEN, mTORC2) with no direct kinase target identified, and the data come from peptide-injected mice. Supporting Evidence: PMID:33554779 MOTS-c elevated the phosphorylation of AKT at Ser 473 PMID:33554779 In MOTS-c-treated mice, the total levels of phosphorylated CK2 substrate were elevated compared with control mice, suggesting CK2 kinase activity is higher in MOTS-c treated mice |
| GO:0072522 purine-containing compound biosynthetic process | IDA PMID:25738459 The mitochondrial-derived peptide MOTS-c promotes metabolic ... | MODIFY | Summary: Metabolomics in MOTS-c-overexpressing and peptide-treated cells showed depletion of 5-methyl-tetrahydrofolate, blockade of de novo purine biosynthesis, more than 20-fold accumulation of the intermediate AICAR and a fall in purines. Reason: The direction of the annotation is wrong - MOTS-c blocks de novo purine biosynthesis rather than contributing to it, and it is not a biosynthetic enzyme in the pathway. A negative-regulation term states the observed effect correctly. The replacement is kept at the regulation level because no direct molecular target in the folate cycle or purine pathway has been identified. Proposed replacements: negative regulation of purine nucleotide biosynthetic process Supporting Evidence: PMID:25738459 5Me-THF depletion was coupled with the blockade of de novo purine biosynthesis PMID:25738459 Its primary target organ appears to be the skeletal muscle, and its cellular actions inhibit the folate cycle and its tethered de novo purine biosynthesis, leading to AMPK activation. |
| GO:0140297 DNA-binding transcription factor binding | IPI PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: MOTS-c co-immunoprecipitated with ATF1 from nuclear extracts, with the interaction strengthened after glucose restriction; ATF1 motifs were enriched in promoters of MOTS-c-upregulated genes. Reason: Co-immunoprecipitation in the compartment where the peptide acts, with a stress-dependent increase and independent motif-enrichment support. ATF1 is a DNA-binding transcription factor, so the term is the informative one for this interaction. Supporting Evidence: PMID:29983246 We found that MOTS-c co-immunoprecipitated with ATF1 in the nucleus and that their interaction was strengthened after GR (3 hr) |
| GO:0140297 DNA-binding transcription factor binding | IPI PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: MOTS-c also interacts with NFE2L1/NRF1, tested because NRF1 shares ARE-dependent stress-response function with NRF2; unlike the NRF2 interaction, this one did not increase with glucose restriction in nuclear extracts and decreased in chromatin extracts. Reason: The interaction is demonstrated with a bona fide DNA-binding transcription factor, which is what the term asserts. It is the weakest of the three partner rows because it is not stress-responsive, but a non-regulated interaction is still an interaction, and the annotation makes no claim about regulation. Supporting Evidence: PMID:29983246 Unlike NRF2, the interaction between MOTS-c and NRF1 was relatively unaltered after GR (3 hr) in nuclear extracts but was decreased in chromatin extracts |
| GO:0140297 DNA-binding transcription factor binding | IPI PMID:29983246 The Mitochondrial-Encoded Peptide MOTS-c Translocates to the... | ACCEPT | Summary: NFE2L2/NRF2 co-immunoprecipitated with MOTS-c specifically from nuclear extracts of stressed cells, confirmed in the reciprocal direction with tagged constructs; the two proteins enter the nucleus independently of one another, so the interaction occurs once both are nuclear. Reason: The best-supported interaction of the peptide - endogenous co-immunoprecipitation plus tagged-construct confirmation, a stress-dependent profile, and downstream support from overlap of MOTS-c-regulated genes with NRF2 ChIP-seq targets. Together with GO:0003677 this is the core molecular function. Supporting Evidence: PMID:29983246 NRF2 co-immunoprecipitated with MOTS-c only from nuclear extracts of cells treated with GR and tBHP for 3 hr PMID:29983246 Further, we confirmed the interaction between MOTS-c and NRF2 by co-immunoprecipitating EGFP-MOTS-c and Myc-NRF2 |
| GO:2001145 negative regulation of phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase activity | IDA PMID:33554779 MOTS-c reduces myostatin and muscle atrophy signaling. | MODIFY | Summary: MOTS-c increased phosphorylation of the PTEN C-terminal Ser380/Thr382/Thr383/Ser385 cluster in mouse skeletal muscle, which the authors interpret as stabilising PTEN while suppressing its phosphatase activity, thereby permitting AKT Ser473 phosphorylation. Reason: The term names the wrong enzyme chemistry. PTEN is a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (GO:0016314), whereas GO:2001145 refers to PIP3 5-phosphatase activity, the INPP5D/SHIP-family reaction, which PTEN does not perform. GO currently has no negative-regulation term for the 3-phosphatase activity, so the correct available term is the parent GO:0010923 negative regulation of phosphatase activity. The underlying claim is also inferred from phospho-site immunoblots rather than a phosphatase assay, and is mediated via CK2, so it is not a core function. Proposed replacements: negative regulation of phosphatase activity Supporting Evidence: PMID:33554779 MOTS-c increased the phosphorylation of the c-terminal cluster of PTEN PMID:33554779 which stabilizes PTEN, resulting in increased protein abundance but suppressed PTEN phosphatase activity |
| GO:0061844 antimicrobial humoral immune response mediated by antimicrobial peptide | IDA PMID:42611943 MOTS-c is a mitochondrial-encoded interferon-linked host def... | NEW | Summary: MOTS-c is an amphipathic cationic peptide that aggregates and damages Escherichia coli and methicillin-resistant Staphylococcus aureus through its hydrophobic core and cationic tail, is induced in human monocytes by interferon gamma and lipopolysaccharide, and neutralises MRSA infectivity in mouse peritonitis; an independent group reported improved survival and reduced bacterial load in MRSA-challenged mice. Reason: Participation test - the peptide itself performs the antibacterial step, acting directly on bacterial surfaces, rather than merely being required for a process another gene product carries out; the activity maps to defined residues whose substitution abolishes it. Comparator test - the canonical secreted human antimicrobial peptide CAMP/LL-37 (P49913) carries GO:0061844 by IDA, so this is the established convention for a circulating cationic amphipathic peptide with direct killing activity, and the absence of such a term for MOTS-c is a gap rather than a convention. The humoral framing fits a peptide already annotated to the extracellular region and measurable in plasma. The in vitro killing assays used 100 micromolar peptide, which is why the molecular-function side (membrane permeabilisation, pore formation) is left unannotated. Supporting Evidence: PMID:42611943 We demonstrate that MOTS-c (mitochondrial open reading frame from the 12 S rRNA type-c) is a mitochondrial-encoded amphipathic and cationic peptide with direct antibacterial and immunomodulatory functions, consistent with the peptide chemistry and functions of known HDPs. PMID:42611943 In human monocytes, interferon gamma (IFNΞ³), lipopolysaccharides (LPS), and differentiation signals each induced the expression of endogenous MOTS-c. PMID:29096170 we demonstrated that a Mitochondria-derived peptide (MOTS-c) could significantly improve the survival rate and decrease bacteria loads in MRSA-challenged mice |
| GO:0050829 defense response to Gram-negative bacterium | IDA PMID:42611943 MOTS-c is a mitochondrial-encoded interferon-linked host def... | NEW | Summary: MOTS-c immediately aggregates Escherichia coli in a dose-dependent manner, damages the bacterial surface as seen by scanning electron microscopy, and inhibits growth; both the hydrophobic core and the cationic tail are required. Reason: Direct action of the peptide on a Gram-negative organism, with structure-function controls. This is the same term that LL-37 carries, and it specifies the organism class that GO:0061844 leaves open. Proposed in addition to, not instead of, GO:0061844 because neither term is an ancestor of the other. Supporting Evidence: PMID:42611943 MOTS-c treatment (0β100 Β΅M) immediately aggregates E. coli in a dose-dependent manner. PMID:42611943 MOTS-c targeted Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA), in part, by targeting their membranes using its hydrophobic and cationic domains. |
| GO:0050830 defense response to Gram-positive bacterium | IDA PMID:42611943 MOTS-c is a mitochondrial-encoded interferon-linked host def... | NEW | Summary: MOTS-c agglutinates methicillin-resistant Staphylococcus aureus in a dose-dependent manner and fully neutralised MRSA infectivity in a mouse model of acute peritonitis; an independent group found improved survival and lower bacterial load in MRSA-infected mice. Reason: Direct action on a Gram-positive organism in vitro plus protection in vivo, corroborated by a separate laboratory. Matches the annotation pattern of other human antimicrobial peptides and is not an ancestor or descendant of the other two proposed terms. Supporting Evidence: PMID:42611943 In a mouse model of acute peritonitis, MOTS-c fully neutralized MRSA infectivity. PMID:29096170 we demonstrated that a Mitochondria-derived peptide (MOTS-c) could significantly improve the survival rate and decrease bacteria loads in MRSA-challenged mice |
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Download this section (compressed HTML)Q: How is a peptide whose ORF lies inside the 12S rRNA actually made? The mitochondrial genetic code reads the ORF as tandem start and stop codons, so translation must occur in the cytosol from an exported mitochondrial transcript, by a route the original paper describes as poorly understood. Until an export mechanism and a cytosolic initiation event are demonstrated, every annotation on this entry rests on an unestablished biosynthetic premise.
Suggested experts: Changhan David Lee, Pinchas Cohen
Q: Has endogenous MOTS-c ever been identified at the peptide level by mass spectrometry, independently of the in-house antibody and ELISA? All localisation and abundance claims (mitochondrial, nuclear, plasma, exercise- and age-dependent changes) depend on those two reagents, and the peptide is only 16 residues long.
Suggested experts: Pinchas Cohen, Troy L Merry
Q: Is the DNA binding of MOTS-c sequence-specific? The EMSA specificity controls substitute the hydrophobic core and the cationic tail, which are also the residues that would drive charge-based binding of any short cationic peptide to DNA, so motif recognition has not been separated from non-specific affinity. The answer decides whether a cis-regulatory-region or sequence-specific DNA binding term is ever justified.
Suggested experts: Kyung Hwa Kim, Changhan David Lee
Q: What is the direct molecular target of MOTS-c in the folate-methionine cycle? The whole metabolic arm of the field - AICAR accumulation, AMPK activation, insulin sensitisation - is attributed to inhibition of this cycle, but no binding partner or inhibited enzyme has been identified, which is why the metabolic annotations have to stay at the regulation level.
Suggested experts: Changhan David Lee, Pinchas Cohen
Q: Do the reported effects occur at physiological peptide concentrations? Cellular work uses 0.5-10 micromolar synthetic peptide (100 micromolar for the antibacterial assays) and animal work 0.5-5 mg/kg/day by injection, while circulating endogenous levels are in the nanogram-per-millilitre range. Which of the phenotypes survive at endogenous concentrations is unresolved and determines which process terms are defensible.
Suggested experts: Troy L Merry, Hiroshi Kumagai
Experiment: Targeted mass spectrometry (parallel reaction monitoring) for the MOTS-c peptide and its predicted proteolytic fragments in human plasma, skeletal muscle and isolated nuclei, with a heavy-isotope-labelled synthetic standard for quantification, in paired samples before and after exercise. A positive result would place the entry's existence beyond the antibody, and would give the absolute concentrations needed to judge which published effects are physiological.
Hypothesis: Endogenous MOTS-c exists as a discrete 16-residue peptide and can be detected without antibody reagents.
Experiment: Express the MOTS-c ORF from a nuclear, codon-optimised construct lacking any 12S rRNA context, with and without the YIFY and RKLR substitutions, in cells depleted of mitochondrial transcripts by actinonin, and test ARE promoter occupancy by ChIP-qPCR and stress-gene induction. Separating peptide from transcript settles whether the reported phenotypes belong on this protein entry at all.
Hypothesis: The nuclear and transcriptional functions require the peptide itself rather than the 12S rRNA transcript or a NUMT-derived product.
Experiment: Competition EMSA and a quantitative binding assay (fluorescence anisotropy or microscale thermophoresis) comparing ARE-containing probes against scrambled probes of identical length and GC content, and against poly-dIdC, at matched ionic strength, using charge-conservative mutants (for example Arg-to-Lys) as controls instead of alanine substitutions. This is the experiment that would license or exclude a sequence-specific DNA binding annotation.
Hypothesis: MOTS-c binding to ARE-containing DNA is charge-driven rather than motif-specific.
Experiment: Determine minimum inhibitory and minimum bactericidal concentrations for MOTS-c against E. coli and MRSA in physiological salt and serum, alongside calcein-leakage and membrane-potential assays on liposomes and on bacteria, and compare with LL-37 as a benchmark. Dose-response data in physiological media would show whether the host-defence role is plausible at endogenous levels, and leakage kinetics would settle whether a pore-forming molecular function term is warranted.
Hypothesis: The antibacterial activity operates at concentrations reachable in vivo and proceeds by membrane permeabilisation.
Experiment: Use a MOTS-c-neutralising antibody or an ORF-targeted antisense approach to lower endogenous peptide levels without ablating all mitochondrial gene expression (the confound in actinonin and rho-zero systems), then measure folate-cycle metabolites, AICAR, AMPK phosphorylation and glucose flux. Loss-of-function at endogenous levels is the missing half of the evidence for every metabolic annotation on this entry.
Hypothesis: The metabolic phenotypes depend on endogenous MOTS-c rather than on pharmacological peptide exposure.
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