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 transmitter release from nerve terminals and intact chromaffin cells and enhances secretion from permeabilized chromaffin cells already maximally stimulated by Ca(2+). In this study we demonstrate that chromaffin cells contain a protein antigenically similar to the cloned Ca(2+)-independent receptor for alpha-latrotoxin. Although this receptor has homology to the secretin family of G-protein-linked receptors, pertussis toxin has no effect on the ability of alpha-latrotoxin to enhance secretion, suggesting that neither G(i) nor G(o) is involved in the response. Furthermore, in the absence of Ca(2+), alpha-latrotoxin does not stimulate polyphosphoinositide-specific phospholipase C. alpha-Latrotoxin specifically enhances ATP-dependent secretion in permeabilized cells. An in situ assay for protein kinase C reveals that alpha-latrotoxin augments the activation of protein kinase C by Ca(2+), and use of protein kinase inhibitors demonstrates that this activation is important for the toxin's enhancing effect. This enhancement of secretion requires Ca(2+) concentrations above 3 microm and is not supported by Ba(2+) or nonhydrolyzable guanine nucleotides, which do not stimulate protein kinase C. We conclude that alpha-latrotoxin stimulates secretion in permeabilized cells by regulating a Ca(2+)- and ATP-dependent event involving protein kinase C.
Bittner
M A
MA
Department of Pharmacology, the University of Michigan Medical School, Ann Arbor 48109, USA. mbittner@umich.edu
Holz
R W
RW
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D002417:Cattle; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015636:Magnesium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D013111:Spider Venoms / Q000494:pharmacology*; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
D013111:Spider Venoms; D015636:Magnesium Chloride; D003208:Concanavalin A; C020763:alpha-latrotoxin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D014357:Trypsin; D002122:Calcium Chloride; D002118:Calcium