Aberrant copper chemistry as a major mediator of oxidative stress in a human cellular model of amyotrophic lateral sclerosis

We have investigated the response to oxidative stress in a model system obt ained by stable transfection of the human neuroblastoma cell line SH-SY5Y w ith plasmids directing constitutive expression of either wild-type human Cu ,Zn superoxide dismutase or a mutant of this enzyme (H46R) associated with familial amyotrophic lateral sclerosis. We report that expression of mutant H46R Cu,Zn superoxide dismutase induces a selective increase in paraquat s ensitivity that is reverted by addition of D-penicillamine. Furthermore, ex pression of this mutant enzyme affects the activity of the endogenous wild- type enzyme both in basal conditions and in copper overloading experiments. Our data indicate that aberrant metal chemistry of this mutant enzyme is t he actual mediator of oxidative stress and that concurrent impairment of th e activity of wild-type endogenous enzyme compromises the cell's ability to respond to oxidative stress.