ATP6V1E2 encodes the E2 subunit of vacuolar H+-ATPase (V-ATPase), a multisubunit enzyme critical for intracellular acidification 1. As a V1 domain component, ATP6V1E2 participates in ATP hydrolysis that powers proton translocation across cellular membranes, maintaining pH homeostasis in intracellular compartments including lysosomes, endosomes, and secretory granules 2. Unlike the testis-specific E1 isoform, ATP6V1E2 is ubiquitously expressed across tissues 1. ATP6V1E2 functions in autophagy regulation, with highest expression in testicular gamete cells where it impacts germ cell development 3. Dysregulation of ATP6V1E2 is associated with disease pathophysiology: genetic variants implicating ATP6V1E2 correlate with cognitive change in aging populations 4, low mRNA/protein expression associates with worse overall survival and advanced clinical stages in renal clear cell carcinoma 5, and upregulation occurs in round spermatids following microwave radiation exposure, contributing to testicular damage and impaired sperm function 6. ATP6V1E2 emerges as a potential diagnostic biomarker and therapeutic target in non-obstructive azoospermia 3 and kidney cancer 5, warranting further investigation into its mechanistic roles in cellular trafficking and metabolic homeostasis.