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.
Dipartimento di Scienze Biomediche, Università di Padova, Viale G. Colombo, 3, 35121, Padova, Italy.
M
M
Cintra-Francischinelli
P
P
Pizzo
L
L
Rodrigues-Simioni
L A
LA
Ponce-Soto
O
O
Rossetto
B
B
Lomonte
J M
JM
Gutiérrez
T
T
Pozzan
C
C
Montecucco
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