Tetanus toxin-mediated cleavage of cellubrevin inhibits proton secretion in the male reproductive tract

Our laboratory has previously shown that the vacuolar H+-ATPase, located in a subpopulation of specialized cells establishes a luminal acidic environment in the epididymis and proximal part of the vas deferens (Breton S, Smith PJS, Lui B, and Brown D. Nat Med 2: 470-472, 1996). Low luminal pH is critical for sperm maturation and maintenance of sperm in a quiescent state during storage in these organs. In the present study we examined the regulation of proton secretion in the epididymis and vas deferens. In vivo microtubule disruption by colchicine induced an almost complete loss of H+-ATPase apical polarity. Endocytotic vesicles, visualized by Texas red-dextran internalization, contain H+-ATPase, indicating active endocytosis of the pump. Cellubrevin, an analog of the vesicle soluble N-ethyl malemide-sensitive factor attachment protein (SNAP) receptor (V-SNARE) synaptobrevin, is highly enriched in H+-ATPase-rich cells of the epididymis and vas deferens, and tetanus toxin treatment markedly inhibited bafilomycin-sensitive proton secretion by 64.3 +/- 9.0% in the proximal vas deferens. Western blotting showed effective cleavage of cellubrevin by tetanus toxin in intact vas deferens, demonstrating that the toxin gained access to cellubrevin. These results suggest that H+-ATPase is actively endocytosed and exocytosed in proton-secreting cells of the epididymis and vas deferens and that net proton secretion requires the participation of the V-SNARE cellubrevin.