The following is a personal account on the significance of this work by Cesare Montecucco: “The work described in this paper was stimulated by a major conundrum in the understanding of the mechanism of action of snake presynaptic PLA2 neurotoxins. The phospholipase A2 activity of snake neurotoxins has been traditionally measured in vitro with a variety of methods generating contrasting results. The situation was enigmatic because there was no correlation whatsoever between the PLA2 turn-over values of the neurotoxins and their animal toxicities. For example, textilotoxin was reported to be the most toxic one and the least PLA2. A second stimulus was provided by the reports of three different laboratories (including our own) that some of these neurotoxins were “seen” inside cells after very few minutes from intoxication, and this contrasted with the expectation that the first lipids that the neurotoxin would interact with are those of the plasma membrane external layer.
We reasoned that at least part of these difficulties could have been solved by measuring directly the neurotoxins hydrolytic activity on live neurons by mass spectrometry and we established a collaboration with one of the leading figures in the field (Prof. A.D. Postle, University of South- ampton, UK). As it rarely happens, the results of this collaboration exceeded expectations and were: (1) A clear indication that the major site of action of the neurotoxins is the outer layer of the plasma membrane. This could be valid for all snake PLA2 toxins acting on cells. (2) The discrepancy between in vitro PLA2 activity and toxicity was found to be much lower when we calculated the PLA2 activity in vivo. (3) Monomeric neurotoxins have shorter life than multi- meric ones on neurons, i.e. notexin and b-bungarotoxin activities “die” within 60 min from the addition to the neurons, whereas taipoxin and textilotoxin act longer. This may happen in vivo as well, suggesting a possible expla- nation for the elevated toxicity of multimeric PLA2 toxins. We felt this was a major advancement of rather general interest and for these reasons chose to publish it in a “Society” journal with a long tradition in reporting on neurotoxins and which makes papers available on line: the Journal of Neurochemistry.”