Calcium plays a key role in the effects induced by a snake venom Lys49 phospholipase A2 homologue on a lymphoblastoid cell line.
A catalytically-inactive Lys49 phospholipase A2 homologue from the venom of the snake Bothrops asper induces diverse effects (necrosis, apoptosis and proliferation) in a lymphoblastoid cell line, depending on the toxin concentration. The increments in cytosolic Ca2+ levels induced by this toxin in this cell line were assessed. At high toxin concentration (100 microg/mL) the toxin induces drastic disruption of the plasma membrane, associated with a prominent Ca2+ influx and necrosis. Previous incubation of the cells with the chelating agent EGTA or with ruthenium red, an inhibitor of the uniporter mitochondrial Ca2+ transport, greatly reduced necrosis. At a toxin concentration of 12.5 microg/mL, apoptosis is the predominant response, being associated with lower increments in cytosolic Ca2+. This effect was inhibited by preincubation with ruthenium red and the cytosolic Ca2+ chelator BAPTA-AM. The proliferative response, which occurs at a low toxin concentration (0.5 microg/mL), is associated with a small and oscillatory increment in cytosolic Ca2+. It was inhibited by EGTA, ruthenium red and BAPTA-AM, by inhibitors of the endoplasmic reticulum Ca2+ -ATPase (SERCA) and by blockade of the ryanodine receptor. It is concluded that necrosis and apoptosis induced by this toxin are associated with increments in cytosolic Ca2+ levels following plasma membrane perturbation, together with the involvement of mitochondria. The cellular proliferative response depends on a limited Ca2+ influx through the plasma membrane, being associated with a concerted functional unit constituted by SERCA, the ryanodine receptor and mitochondria, which regulate the observed oscillations in cytosolic Ca2+ concentration.
Mora
Rodrigo
R
Departamento de Microbiología e Inmunología, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.
Maldonado
Alexis
A
Valverde
Berta
B
Gutiérrez
José María
JM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008214:Lymphocytes / Q000166:cytology*; D008239:Lysine / Q000737:chemistry*; D008928:Mitochondria / Q000378:metabolism; D009336:Necrosis / Q000139:chemically induced; D010741:Phospholipases A / Q000378:metabolism / Q000633:toxicity*; D054467:Phospholipases A2; D012430:Ruthenium Red / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012910:Snake Venoms / Q000201:enzymology / Q000633:toxicity*; D013997:Time Factors
D002614:Chelating Agents; D019837:Ryanodine Receptor Calcium Release Channel; D012910:Snake Venoms; D012430:Ruthenium Red; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D000252:Calcium-Transporting ATPases; D008239:Lysine; D002118:Calcium