The phosphoinositide PI5P impairs mitochondrial function through endosome-mitochondria proximity

Alterations of mitochondrial structure and bioenergetic dysfunction are hallmarks of metabolic stress and in the progression of heart failure (HF). However, the impact of lipid signalling, particularly the dynamics of phosphoinositides is not fully characterized. Here, we investigate the effect of phosphatidylinositol 5-phosphate (PI5P) on mitochondrial structure and function in cardiomyocytes. We show that exogenous PI5P induces mitochondrial fragmentation, loss of mitochondrial membrane potential, increased ROS production, and impaired mitochondrial respiration. Using a PI5P biosensor, we identify a significant mitochondrial PI5P pool, whose abundance increases upon metabolic stress induced by 2-deoxy-D-glucose exposure, most likely in a PIKfyve-dependent manner. Furthermore, we demonstrate that PIKfyve-positive endolysosomes localize in close proximity to mitochondria in an actin-dependent manner, suggesting a spatial and functional coupling between these two organelles. Overall, our findings reveal a novel mechanism by which PI5P contributes to mitochondrial dysfunction during metabolic stress, potentially linking endolysosomal signalling to mitochondrial metabolism and cardiomyocyte bioenergetic status.