Calcium imaging of muscle cells treated with snake myotoxins reveals toxin synergism and presence of acceptors.
Snake myotoxins have a great impact on human health worldwide. Most of them adopt a phospholipase A2 fold and occur in two forms which often co-exist in the same venom: the Asp49 toxins hydrolyse phospholipids, whilst Lys49 toxins are enzymatically inactive. To gain insights into their mechanism of action, muscle cells were exposed to Bothrops myotoxins, and cytosolic Ca(2+) and cytotoxicity were measured. In both myoblasts and myotubes, the myotoxins induced a rapid and transient rise in cytosolic [Ca(2+)], derived from intracellular stores, followed, only in myotubes, by a large Ca(2+) influx and extensive cell death. Myoblast viability was unaffected. Notably, in myotubes Asp49 and Lys49 myotoxins acted synergistically to increase the plasma membrane Ca(2+) permeability, inducing cell death. Therefore, these myotoxins may bind to acceptor(s) coupled to intracellular Ca(2+) mobilization in both myoblasts and myotubes. However, in myotubes only, the toxins alter plasma membrane permeability, leading to death.
Cintra-Francischinelli
M
M
Dipartimento di Scienze Biomediche, Università di Padova, Viale G. Colombo, 3, 35121, Padova, Italy.
Pizzo
P
P
Rodrigues-Simioni
L
L
Ponce-Soto
L A
LA
Rossetto
O
O
Lomonte
B
B
Gutiérrez
J M
JM
Pozzan
T
T
Montecucco
C
C
D000818:Animals; D017837:Bothrops; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003435:Crotalid Venoms / Q000032:analysis* / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D051189:Murinae; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D003435:Crotalid Venoms; D002118:Calcium