MOTS-c

MOTS-c (Mitochondrial Open reading frame of the 12S rRNA-c) is a 16-amino acid peptide derived from the mitochondrial genome. While mitochondria are known for ATP production, the discovery of peptides like MOTS-c suggests mitochondria may also act as signaling organelles that encode and secrete bioactive peptides, which have been observed to regulate nuclear gene expression and systemic metabolism.

Discovery and Significance

MOTS-c is encoded by a short open reading frame within the mitochondrial 12S ribosomal RNA gene, a region of the mitochondrial genome not previously known to encode functional peptides. This finding contributed to the investigation of the 'mitochondrial peptidome.'

Retrograde Signaling

The age-related decline in MOTS-c levels has been correlated with changes in metabolic function. MOTS-c is described as a retrograde signaling molecule, meaning it may carry signals from mitochondria to the nucleus to coordinate cellular responses to metabolic conditions.

Under conditions of metabolic stress like glucose restriction, MOTS-c has been observed to translocate from the cytoplasm into the cell nucleus. In the nucleus, it has been shown to regulate the expression of genes involved in metabolism, cellular stress responses, and adaptation. This mitochondrial-nuclear communication pathway may allow the metabolic state of mitochondria to influence cellular and systemic physiology.

MOTS-c is reported to exert metabolic regulatory effects through several mechanisms, including its function as a mitochondrial-to-nuclear retrograde signal.

Nuclear Translocation

A proposed mechanism involves its translocation to the nucleus during metabolic stress conditions. While MOTS-c is present in the cytoplasm under basal conditions, it has been observed to accumulate in the nucleus when cells are subjected to metabolic challenges such as glucose deprivation or oxidative stress.

Once in the nucleus, MOTS-c has been found to bind to specific DNA regulatory regions and interact with transcription factors, altering gene expression. Research has indicated that nuclear MOTS-c regulates the expression of genes involved in cellular stress responses, antioxidant defenses, and metabolic adaptation.

AMPK Activation

One reported effect of MOTS-c is the activation of the AMPK (AMP-activated protein kinase) pathway, a key component in cellular energy homeostasis. AMPK activation by MOTS-c may occur through both direct and indirect mechanisms.

This activation can lead to a cascade of downstream events, such as increased glucose uptake in skeletal muscle models through GLUT4 translocation, increased fatty acid oxidation, and effects on mitochondrial biogenesis. It has also been associated with changes in insulin sensitivity at cellular and systemic levels in research models.

Metabolic Effects

In skeletal muscle models, MOTS-c has been shown to increase glucose uptake and utilization, including in models of insulin resistance. The peptide also appears to influence mitochondrial quality control through effects on mitophagy and mitochondrial dynamics.

At the enzyme level, MOTS-c has been reported to inhibit the folate cycle enzyme MTHFD1L, leading to metabolic reprogramming. The peptide also modulates inflammatory responses and oxidative stress in some models, potentially through its effects on NF-κB signaling and antioxidant enzyme expression.

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Research Limitations

Published observations involving other preparations, experimental systems, or study populations do not establish the identity, performance, or suitability of this research material for any particular experiment.