Alpha-latrotoxin triggers extracellular Ca(2+)-dependent exocytosis and sensitizes fusion machinery in endocrine cells.
alpha-Latrotoxin from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca(2+) influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca(2+), and Ca(2+) microfluorometry and amperometry, we investigated the stimulating effect and mechanism of alpha-latrotoxin on exocytosis in rat pancreatic beta cells, LbetaT2 cells and latrophilin plasmid-transfected INS-1 cells. Our data indicated that: (1) alpha-latrotoxin increased cytosolic Ca(2+) concentration through the formation of cation-permitting pores and subsequent Ca(2+) influx with the presence of extracellular Ca(2+); (2) alpha-latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca(2+)-free bath solution; and (3) alpha-latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca(2+) photolyzed by a flash of ultraviolet light. In summary, alpha-latrotoxin induced exocytosis by way of Ca(2+) influx and accelerated vesicle fusion by the sensitization of fusion machinery.
Hu
Zhi-Tao
ZT
School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
Zhao
Ping
P
Liu
Jie
J
Wu
Zheng-Xing
ZX
Xu
Tao
T
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002478:Cells, Cultured; D005089:Exocytosis / Q000187:drug effects*; D045604:Extracellular Fluid / Q000378:metabolism; D007340:Insulinoma / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008561:Membrane Fusion / Q000187:drug effects*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018000:Receptors, Peptide / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013111:Spider Venoms / Q000494:pharmacology*
D018000:Receptors, Peptide; D013111:Spider Venoms; C034800:alpha-latrotoxin receptor; C020763:alpha-latrotoxin; D011493:Protein Kinase C; D002118:Calcium