The V-ATPase V1 subunit A1 is required for rhodopsin anterograde trafficking in Drosophila

Synthesis and maturation of the light sensor, rhodopsin, are critical for the maintenance of light sensitivity and for photoreceptor homeostasis. In Drosophila, the main rhodopsin, Rh1, is synthesized in the endoplasmic reticulum and transported to the rhabdomere through the secretory pathway. In an unbiased genetic screen for factors involved in rhodopsin homeostasis, we identified mutations in vha68-1, which encodes the vacuolar proton-translocating ATPase (V-ATPase) catalytic subunit A isoform 1 of the V1 component. Loss of vha68-1 in photoreceptor cells disrupted post-Golgi anterograde trafficking of Rh1, reduced light sensitivity, increased secretory vesicle pH, and resulted in incomplete Rh1 deglycosylation. In addition, vha68-1 was required for activity-independent photoreceptor cell survival. Importantly, vha68-1 mutants exhibited phenotypes similar to those exhibited by mutations in the V0 component of V-ATPase, vha100-1. These data demonstrate that the V1 and V0 components of V-ATPase play key roles in post-Golgi trafficking of Rh1 and that Drosophila may represent an important animal model system for studying diseases associated with V-ATPase dysfunction.