TMEM175 deficiency impairs autophagic degradation and alleviates mitochondrial oxidative damage in cardiomyocytes through AMPK activation.

Transmembrane protein 175 (TMEM175) is a lysosomal proton-activated and proton-selective channel critical for regulating lysosomal membrane potential and acidity. However, its role in cardiomyocyte physiological and stress response remains unclear. Here, we investigated the function of TMEM175 in mitochondrial homeostasis using H9c2 cardiomyocytes and neonatal rat ventricular myocytes (NRVMs) under physiological conditions and during hydrogen peroxide (H2O2)-induced oxidative stress. Under physiological conditions, genetic knockout of TMEM175 impaired mitochondrial respiration, reduced mitochondrial superoxide, and attenuated autophagic clearance. In contrast, under H2O2-induced stress, TMEM175 deletion significantly alleviated mitochondrial dysfunction and cell death, despite autophagic flux being primarily stalled at the degradation stage. Mechanistically, TMEM175 deficiency activated AMP-activated protein kinase (AMPK), and silencing AMPK reversed the cytoprotective effects of TMEM175 deletion against H2O2 injury. Pharmacological inhibition of TMEM175 with 2-phenylpyridin-4-ylamine (2-PPA) in H9c2 and NRVMs recapitulated key phenotypes observed in genetic knockout models. Furthermore, 2-PPA improved cardiac function and attenuated histopathological injury in myocardial infarction mice. Together, these findings reveal a dual role for TMEM175: it maintains lysosomal-mitochondrial communication under basal conditions, yet its inhibition protects against oxidative stress primarily through AMPK activation. This study identifies TMEM175 as a novel lysosomal regulator of cardiac mitochondrial resilience and highlights its potential role in the cellular response to oxidative injury in cardiomyocytes.