A human mitochondrial isoform of TRPV1 regulates intracellular Ca2+ simultaneously with mitochondrial thermolysis

Mitochondria are the cornerstones of cellular and body thermogenesis, with an inner temperature possibly reaching 50 degrees. Here, we report the identification of a human Transient Receptor Potential Vanilloid 1 alternative isoform located in mitochondria. This isoform, which we have termed mitoTRPV1, acts as a thermostat to restrict the mitochondrial temperature. The mitoTRPV1 open reading frame overlaps TRPV1 exons 1 and 2 and intron 2 in a +1 frame, encoding for a predicted 150 amino-acid N-terminal mitochondrial targeting sequence (MTS) conserved amongst mammalian species, followed by the 687 amino acids of TRPV1 C-terminal. This ORF is ubiquitously expressed in most human organs, underscoring its broad relevance. The deduced MTS, conserved among mammalian species, effectively addresses this TRPV1 isoform to the mitochondrial inner membrane. Our experiments, using heterologous wild-type and mutated mitoTRPV1 expression, combined with Ca2+ imaging, mitochondrial temperature and oxygraphy measurements, disclosed that mitoTRPV1 activation induces Ca2+ efflux and mitochondrial cooling, without modification of mitochondrial respiration and ATP production. Notably, the loss of function mitoTRPV1-G684V isoform, responsible for exertional heat stroke predisposition in humans, abolished mitochondrial Ca2+ efflux and cooling. These findings reveal a new thermolysis function for TRPV1 in preventing mitochondrial overwarming while not affecting the OXPHOS efficiency. They also highlight the potential implications of mitoTRPV1 in human diseases related to temperature dysregulation.