title: Mitochondrial dysfunction in Parkinson disease: evidence in mutant PARK2 fibroblasts.
abstract: Mutations in PARK2, encoding Parkin, cause an autosomal recessive form of juvenile Parkinson Disease (JPD). The aim of the present study was to investigate the impact of PARK2 mutations on mitochondrial function and morphology in human skin fibroblasts. We analyzed cells obtained from four patients clinically characterized by JPD, harboring recessive mutations in PARK2. By quantitative PCR we found a reduction (<50%) of PARK2 transcript in all patients but one; however Western Blot analysis demonstrated the virtual absence of Parkin protein in all mutant fibroblasts. Respiration assays showed an increment of oxygen consumption, which was uncoupled to ATP cellular levels. This finding was probably due to presence of altered mitochondrial membrane potential (ΔΨm), confirmed by JC-1 analysis. The mitochondrial network was comparable between mutant and control cells but, interestingly, a "chain-like" network was found only in mutant fibroblasts. Dissipation of ΔΨm usually leads to mitochondrial fragmentation in healthy cells and eventually to mitophagy; however, this behavior was not observed in patients' fibroblasts. The absence of mitochondrial fragmentation in mutant Parkin fibroblasts could results in accumulation of damaged mitochondria not targeted to mitophagy. This condition should increase the oxidative stress and lead to cellular dysfunction and death. Our results suggest that PARK2 mutations cause mitochondrial impairment, in particular reduction in ATP cellular levels and alteration of ΔΨm, even in non-neuronal cells and confirm the hypothesis that Parkin holds a pivotal role in pro-fission events.
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Maria C
authors: MC
authors: Zanellati
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Valentina
authors: V
authors: Monti
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Chiara
authors: C
authors: Barzaghi
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Chiara
authors: C
authors: Reale
authors: Unit of Child Neurology, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Nardo
authors: N
authors: Nardocci
authors: Neurology Unit, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Alberto
authors: A
authors: Albanese
authors: Casa Sollievo Della Sofferenza Hospital, Mendel Institute Rome, Italy.
authors: Enza M
authors: EM
authors: Valente
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Daniele
authors: D
authors: Ghezzi
authors: Unit of Molecular Neurogenetics - Pierfranco and Luisa Mariani Center for the Study of Mitochondrial Disorders in Children, Foundation of the Carlo Besta Neurological Institute IRCCS, Milan, Italy.
authors: Barbara
authors: B
authors: Garavaglia
keywords: PARK2; mitochondrial dynamics; mitochondrial membrane potential; oxygen consumption; parkin