Increased SOD1 association with chromatin, DNA damage, p53 activation, and apoptosis in a cellular model of SOD1-linked ALS

Mutations in the gene encoding cytosolic Cu,Zn-superoxide dismutase (SOD1) have been linked to familial amyotrophic lateral sclerosis (FALS). However the molecular mechanisms of motor neuron death are multifactorial and remain unclear. Here we examined DNA damage;p53 activity and apoptosis in SH-SY5Y human neuroblastoma cells transfected to achieve low-level expression of either wild-type or mutant Gly(93) --> Ala (G93A) SOD1, typical of FALS. DNA damage was investigated by evaluating the levels of 8-oxo-7,8-dihydro-2`-deoxyguanosine (8-oxodGuo) and DNA strand breaks. Significantly higher levels of DNA damage, increased p53 activity, and a greater percentage of apoptotic cells were observed in SH-SY5Y cells transfected with G93A SOD1 when compared to cells overexpressing wild-type SOD1 and untransfected cells. Western blot, FACS, and confocal microscopy analysis demonstrated that G93A SOD1 is present in the nucleus in association with DNA. Nuclear G93A SOD1 has identical superoxide dismutase activity but displays increased peroxidase activity when compared to wild-type SOD1. These results indicate that the G93A mutant SOD1 association with DNA might induce DNA damage and trigger the apoptotic response by activating p53. This toxic activity of mutant SOD1 in the nucleus may play an important role in the complex mechanisms associated with motor neuron death observed in ALS pathogenesis. (C) 2010 Elsevier B.V. All rights reserved.

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP (Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional para o Desenvolvimento Cientifico e Tecnologico - CNPq

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Instituto do Milenio - Redoxoma (Brazil)

Instituto do Milenio - Redoxoma (Brazil)

Financiadora de Estudos e Projetos - FINEP (Brazil)

Financiadora de Estudos e Projetos (FINEP)

INCT de Processos Redox em Biomedicina

INCT de Processos Redox em Biomedicina

Pro-Reitoria de Pesquisa da Universidade de Sao Paulo (USP) (Brazil)

Pro-Reitoria de Pesquisa da Universidade de Sao Paulo (USP) (Brazil)

Italian Ministry of Health

Italian Ministry of Health