Abstract

FAM162A is an inner mitochondrial protein known for its role in hypoxia-induced apoptosis. However, it is often overexpressed in cancer, where its pro-apoptotic function appears to be overridden, suggesting novel unknown roles in mitochondrial function and cell survival. Furthermore, its precise localization, topology, and orientation remain controversial. In this study, we aimed to assess the role of FAM162A in mitochondrial structure, dynamics, and bioenergetics and its impact on cellular and organismal stress resistance, while also establishing its localization, topology, and orientation. To this end, localization, topology, and orientation were determined by protease-protection assays in COS7 cells. In vitro loss- and gain-of-function experiments assessed mitochondrial structure and function by confocal microscopy, immunoblotting, and Seahorse analysis, while a transgenic Drosophila model overexpressing human FAM162A was generated to evaluate organismal survival under normal and heat stress conditions. We found that FAM162A localized to the inner mitochondrial membrane, predominantly within the cristae, and supported cristae ultrastructure, bioenergetics, and mitochondrial turnover, thereby enhancing oxidative metabolism, cell viability, and stress resistance. FAM162A expression was positively associated with the fusion protein OPA1 and interacted with OPA1 to regulate the proportion of long- and short-OPA1 isoforms. Transgenic Drosophila overexpressing human FAM162A exhibited increased lifespan and locomotor activity under both normal and heat stress conditions. Overall, FAM162A emerges as a key regulator of mitochondrial integrity and bioenergetics through its association with OPA1, confirming a novel role in cellular health and stress resistance.