miR-125b controls mitochondrial metabolism and dynamics by targeting BIK and MTP18

Abnormal mitochondria metabolism and innate immune responses participate in the pathogenesis of many inflammatory disorders. The molecular events regulating mitochondrial activity to control survival and cell death in monocytes/macrophages are poorly understood. Here we show that miR-125b attenuates the activity of the mitochondrial respiratory chain through BIK silencing, and promotes the elongation of mitochondrial network through MTP18 targeting, without impacting autophagy, in the human monocytes. Proinflammatory activation is associated with a concomitant increase in miR-125b expression, decrease in BIK and MTP-18 expression, reduced oxidative phosphorylation, and enhanced mitochondrial fusion. Furthermore, expression of M1-associated transcripts as well as mitochondrial dynamics and energy metabolism are induced upon ectopic expression of miR-125b. In turn, by repressing miR-125b, mitochondrial dynamics was preserved, LPS-induced repression of BIK expression and of mitochondrial respiration were prevented, and M1 polarization of macrophages was inhibited. Altogether, our data reveal a novel role for miR-125b in controlling mitochondrial metabolism and dynamics by targeting BIK and MTP18, respectively, two novel cellular target proteins involved in maintaining the mitochondrial integrity in human monocytes. These findings not only suggest a novel function for miR-125b in regulating metabolic adaptation of monocytes to inflammation but also unravel new molecular mechanisms for its pro-apoptotic role and identify potential targets for interfering with inflammatory activation of monocytes.

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Duroux-Richard I, Roubert C, Ammari M, Présumey J, Grün JR, Häupl T, Grützkau A, Lecellier CH, Boitez V, Codogno P, Escoubet J, Pers YM, Jorgensen C, Apparailly F