Latrotoxin-induced exocytosis in mast cells transfected with latrophilin.
α-Latrotoxin (α-LTX) is known to cause massive exocytosis from presynaptic nerve terminals. We investigated the effects of α-LTX on exocytotic release from mast cells, typical non-neuronal secretory cells. When we transfected mast cells with latrophilin, a specific receptor for α-LTX, α-LTX caused intracellular Ca(2+) to increase and led to exocytosis in the presence of extracellular Ca(2+). On the other hand, neither Ca(2+) increase nor exocytosis was observed in the absence of extracellular Ca(2+). These results indicate that α-LTX, together with latrophilin, works as a Ca(2+) ionophore. However, α-LTX had additional effects on signal transduction in mast cells. We found that inhibitors of protein kinase C (PKC) partially suppressed exocytosis. Furthermore, several soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, including SNAP-23, were phosphorylated by α-LTX. These results suggest that exocytosis induced by α-LTX can be explained by (1) elevation of intracellular Ca(2+), (2) phosphorylation of SNARE proteins including SNAP-23, syntaxin-4 and VAMP-8 through PKC-dependent and -independent pathways. Our study may provide a new system to investigate the action of α-LTX and the mechanism of exocytosis in mast cells.
Hiramatsu
Hiroyuki
H
Graduate School of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
Tadokoro
Satoshi
S
Nakanishi
Mamoru
M
Hirashima
Naohide
N
D000818:Animals; D001740:Black Widow Spider / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D002460:Cell Line; D005089:Exocytosis / Q000187:drug effects*; D007476:Ionophores / Q000494:pharmacology; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D018000:Receptors, Peptide / Q000235:genetics* / Q000378:metabolism; D013111:Spider Venoms / Q000494:pharmacology*; D014162:Transfection
D007476:Ionophores; D018000:Receptors, Peptide; D013111:Spider Venoms; C034800:alpha-latrotoxin receptor; C020763:alpha-latrotoxin; D011493:Protein Kinase C; D002118:Calcium