A Ca2+-independent receptor for alpha-latrotoxin, CIRL, mediates effects on secretion via multiple mechanisms.
alpha-Latrotoxin (alpha-Ltx), a component of black widow spider venom, stimulates secretion from nerve terminals and from PC12 cells. In this study we examine the effects of expression of a newly cloned Ca2+-independent receptor for alpha-Ltx (CIRL) on secretion from bovine chromaffin cells. We first characterized the effect of alpha-Ltx on secretion from untransfected cells. alpha-Ltx, by binding in a Ca2+-independent manner to an endogenous receptor, causes subsequent Ca2+-dependent secretion from intact cells. The stimulation of secretion is correlated with Ca2+ influx caused by the toxin. In permeabilized cells in which the Ca2+ concentration is regulated by buffer, alpha-Ltx also enhances Ca2+-dependent secretion, indicating a direct role of the endogenous receptor in the secretory pathway. Expression of CIRL increased the sensitivity of intact and permeabilized cells to the effects of alpha-Ltx, demonstrating that this protein is functional in coupling to secretion. Importantly, in the absence of alpha-Ltx, the expression of CIRL specifically inhibited the ATP-dependent component of secretion in permeabilized cells without affecting the ATP-independent secretion. This suggests that this receptor modulates the normal function of the regulated secretory pathway and that alpha-Ltx may act by reversing the inhibitory effects of the receptor.
Bittner
M A
MA
Department of Pharmacology, The University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
Krasnoperov
V G
VG
Stuenkel
E L
EL
Petrenko
A G
AG
Holz
R W
RW
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D019439:Chromaffin Cells / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D004072:Digitonin; D004533:Egtazic Acid / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D007668:Kidney / Q000166:cytology; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology
D002395:Catecholamines; D002614:Chelating Agents; D009419:Nerve Tissue Proteins; D018000:Receptors, Peptide; D013111:Spider Venoms; C034800:alpha-latrotoxin receptor; D004533:Egtazic Acid; C020763:alpha-latrotoxin; D000255:Adenosine Triphosphate; D004072:Digitonin; D002118:Calcium