Coding and non-coding roles of MOCCI (C15ORF48) coordinate to regulate host inflammation and immunity

Mito-SEPs are small open reading frame-encoded peptides that localize to the mitochondria to regulate metabolism. Motivated by an intriguing negative association between mito-SEPs and inflammation, here we screen for mito-SEPs that modify inflammatory outcomes and report a mito-SEP named Modulator of cytochrome C oxidase during Inflammation (MOCCI) that is upregulated during inflammation and infection to promote host-protective resolution. MOCCI, a paralog of the NDUFA4 subunit of cytochrome C oxidase (Complex IV), replaces NDUFA4 in Complex IV during inflammation to lower mitochondrial membrane potential and reduce ROS production, leading to cyto-protection and dampened immune response. The MOCCI transcript also generates miR-147b, which targets the NDUFA4 mRNA with similar immune dampening effects as MOCCI, but simultaneously enhances RIG-I/MDA-5-mediated viral immunity. Our work uncovers a dual-component pleiotropic regulation of host inflammation and immunity by MOCCI (C15ORF48) for safeguarding the host during infection and inflammation. Mito-SEPs are small peptides that can modulate oxidative metabolism in mitochondria. Here the authors show that C15ORF48 encodes a mito-SEP, MOCCI, capable of altering mitochondria respiration to suppress inflammation, while C15ORF48 3' untranslated region also contains a miRNA, miR-147b, that synergizes with MOCCI to modulate host anti-viral responses.

Automated summary

The study identifies a mito-SEP named MOCCI, which can replace NDUFA4 during inflammation to reduce mitochondrial membrane potential and ROS production, providing cell protection and suppressing immune responses. Additionally, the MOCCI transcript generates miR-147b, which enhances antiviral immune responses.