OMEGA-CONOTOXIN AND CD2-OPERATED CA2+ CHANNELS( STIMULATE THE RECRUITMENT TO THE PLASMAMEMBRANE OF AN INTRACELLULAR POOL OF VOLTAGE)

I-125-omega-conotoxin binding to neuroblastoma cells at 37 degrees C c ontinously increased, reaching a plateau after 6-8 hr; this was up to 6 times higher than that observed at lower temperatures. The same effe ct was induced by short pulses with omega-conotoxin followed by a chas e period at 37 degrees C in control medium. Cd2+ also induced up-regul ation of surface I-125-omega-conotoxin-binding sites. Fura-2 and patch -clamp experiments showed that the recruited binding sites corresponde d to functional voltage-operated Ca2+ channels. Permeabilization exper iments revealed a large intracellular pool of I-125-omega-conotoxin-bi nding sites, whose recruitment to the plasmamembrane was prevented by brefeldin A and nocodazole. These data suggest that specific stimuli m ight induce voltage-operated Ca2+ channel translocation to plasmamembr ane and, in this way, modulate presynaptic events.