Latrotoxin stimulates secretion in permeabilized cells by regulating an intracellular Ca2+- and ATP-dependent event - A role for protein kinase C

alpha-latrotoxin, a component of black widow spider venom, stimulates trans mitter release from nerve terminals and intact chromaffin cells and enhance s secretion from permeabilized chromaffin cells already maximally stimulate d by Ca2+. In this study we demonstrate that chromaffin cells contain a pro tein antigenically similar to the cloned Ca2+-independent receptor for alph a-latrotoxin. Although this receptor has homology to the secretin family of G-protein-linked receptors, pertussis toxin has no effect on the ability o f alpha-latrotoxin to enhance secretion, suggesting that neither G(i) nor G (o) is involved in the response. Furthermore, in the absence of Ca2+, alpha -latrotoxin does not stimulate polyphosphoinositide-specific phospholipase C. alpha-Latrotoxin specifically enhances ATP-dependent secretion in permea bilized cells. An in situ assay for protein kinase C reveals that alpha-lat rotoxin augments the activation of protein kinase C by Ca2+, and use of pro tein kinase inhibitors demonstrates that this activation is important for t he toxin's enhancing effect. This enhancement of secretion requires Ca2+ co ncentrations above 3 mu M and is not supported by Ba2+ or nonhydrolyzable g uanine nucleotides, which do not stimulate protein kinase C, We conclude th at cu-latrotoxin stimulates secretion in permeabilized cells by regulating a Ca2+- and ATP-dependent event involving protein kinase C.