ω-conotoxin and Cd 2+ stimulate the recruitment to the plasmamembrane of an intracellular pool of voltage-operated Ca 2+ channels

Abstract

125I-ω-conotoxin binding to neuroblastoma cells at 37°C continously increased, reaching a plateau after 6–8 hr; this was up to 6 times higher than that observed at lower temperatures. The same effect was induced by short pulses with w-conotoxin followed by a chase period at 37°C in control medium. Cd 2+ also induced up-regulation of surface 125I-ω-conotoxin-binding sites. Fura-2 and patch-clamp experiments showed that the recruited binding sites corresponded to functional voltage-operated Ca 2+ channels. Permeabilization experiments revealed a large intracellular pool of 125I-ω-conotoxin-binding sites, whose recruitment to the plasmamembrane was prevented by brefeldin A and nocodazole. These data suggest that specific stimuli might induce voltage-operated Ca 2+ channel translocation to plasmamembrane and, in this way, modulate presynaptic events.