<p>Exposure to cold environments is physiologically challenging, with extreme cold stress (ECS) impairing the function of the left ventricle (LV) of the heart. We aimed to determine the role and mechanism of action of the miR-499-5p/phosphofurin acidic cluster sorting protein 2 (PACS2)/transient receptor potential cation channel subfamily V member 1 (TRPV1) axis in ECS-induced cardiomyocyte injury and LV dysfunction. Mice were placed in a –20 °C chamber to simulate an extremely cold environment. MiR-499-5p overexpression in the mice decreased PACS2 levels, and mitochondrial function was inhibited in vivo following ECS. Inhibiting miR-499-5p enhanced PACS2 expression, thereby reversing the structural and functional LV deficits caused by ECS. Cardiac-specific <i>Pacs2</i> knock-in restored the decreases in mitophagy and mitochondrial energy metabolism caused by ECS via enhancing endoplasmic reticulum–mitochondrial calcium flux through TRPV1, a nonselective calcium channel. The findings indicate targets for preventing cardiac disease during exposure to extremely cold environments.</p> Graphical Abstract <p>Schematic depiction of the pathway by which PACS2 modulates left cardiac dysfunction under extreme cold exposure.</p> <p>ECS diminishes the expression of PACS2, leading to a decrease in MAM formation, and [Ca²⁺]m flux through TRPV1. Consequently, this results in the inhibition of mitophagy and impairment of mitochondrial energy metabolism. This novel mechanism underlies the cardiomyocyte injury and left cardiac dysfunction induced by ECS.</p> <p>ECS, extreme cold stress; PACS2, phosphofurin acidic cluster sorting protein; TRPV1, transient receptor potential cation channel subfamily V member 1; MAM, mitochondria-associated membrane; [Ca²⁺]m, mitochondrial calcium.</p> <p></p>