Dusp15 Dephosphorylates mtHsp70 at Thr116 to Prevent Its Proteasomal Degradation and Maintain Mitochondrial Unfolded Protein Response in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) is driven by mitochondrial dysfunction and impaired proteostasis. This study investigates Dusp15’s role in regulating the mitochondrial unfolded protein response (mito-UPR) via its interaction with mtHsp70 and explores its therapeutic potential in DCM. Transcriptomic and proteomic analyses identified Dusp15 as a critical regulator in DCM. Overexpression of Dusp15 preserved cardiac function, reduced fibrosis and inflammation, and stabilized mitochondrial function while Dusp15 deficiency exacerbated these pathologies. Mechanistically, Dusp15 interacted with the N-terminal binding domain (NBD) of mtHsp70 via its phosphatase domain, targeting Thr116 within the TFY motif for dephosphorylation. This prevented mtHsp70 proteasomal degradation, maintained mito-UPR activity, mitochondrial membrane potential, and redox balance. mtHsp70 phosphorylation-deficient mice ( mtHsp70T116A ) mice resisted hyperglycemia-induced myocardial dysfunction, fibrosis, and inflammation, while phosphorylation-mimetic T116D mutants negated Dusp15-mediated cardioprotection. Therapeutically, a drug screen integrating RNA sequencing and pathway scoring identified dapagliflozin (DAPA) as a cardioprotective candidate. DAPA upregulated Dusp15, stabilized mtHsp70, and improved cardiac outcomes, effects absent in Dusp15 ^Cko mice. Inhibition of mito-UPR negated Dusp15 and DAPA benefits. Dusp15 preserves mitochondrial integrity and cardiac function in DCM by dephosphorylating mtHsp70 at Thr116. Targeting the Dusp15/mtHsp70 axis, including with DAPA, offers a promising strategy for DCM treatment.