Mutant Cu,Zn superoxide dismutases and familial amyotrophic lateral sclerosis: evaluation of oxidative hypotheses.

FALS-associated missense mutations of SOD1 exhibit a toxic gain of function that leads to the death of motor neurons. The explanations for this toxicity fall into two broad categories. One involves a gain of some oxidative activity, while the second involves a gain of protein: protein interactions. Among the postulated oxidative activities are the following: (i) peroxidase action; (ii) superoxide reductase action; and, (iii) the enhancement of production of O2- by partial reversal of the normal SOD activity, which then leads to increased formation of ONOO(-). We will herein concentrate on evaluating the relative merits of these oxidative hypotheses and consider whether the experiments with transgenic animals that purport to disprove these oxidative explanations really do so.