PT  - JOURNAL ARTICLE
AU  - Jacqueline M. Tokarew
AU  - Daniel N. El-Kodsi
AU  - Nathalie A. Lengacher
AU  - Travis K. Fehr
AU  - Angela P. Nguyen
AU  - Bojan Shutinoski
AU  - Brian O’Nuallain
AU  - Ming Jin
AU  - Jasmine M. Khan
AU  - Andy C. H. Ng
AU  - Juan Li
AU  - Qiubo Jiang
AU  - Mei Zhang
AU  - Liqun Wang
AU  - Rajib Sengupta
AU  - Kathryn R. Barber
AU  - An Tran
AU  - Stephanie Zandee
AU  - Xiajun Dong
AU  - Clemens R. Scherzer
AU  - Alexandre Prat
AU  - Eve Tsai
AU  - Masashi Takanashi
AU  - Nobutaka Hattori
AU  - Jennifer A. Chan
AU  - Luigi Zecca
AU  - Andrew B. West
AU  - Arne Holmgren
AU  - Lawrence Puente
AU  - Gary S. Shaw
AU  - Gergely Toth
AU  - John M. Woulfe
AU  - Peggy Taylor
AU  - Julianna J. Tomlinson
AU  - Michael G. Schlossmacher
TI  - Age-Associated Insolubility of Parkin in Human Midbrain is Linked to Redox Balance and Sequestration of Reactive Dopamine Metabolites
AID  - 10.1101/2020.11.20.392175
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.11.20.392175
4099  - http://biorxiv.org/content/early/2020/11/21/2020.11.20.392175.short
4100  - http://biorxiv.org/content/early/2020/11/21/2020.11.20.392175.full
AB  - The mechanisms by which parkin protects the adult human brain from Parkinson disease remain incompletely understood. We hypothesized that parkin cysteines participate in redox reactions, which are reflected in its posttranslational modifications. We found that in human control brain, including the S. nigra, parkin is largely insoluble after age 40 years, which is linked to its oxidation, e.g., at Cys95 and Cys253. In mice, oxidative stress increases posttranslational modifications at parkin cysteines and reduces its solubility. Oxidation of recombinant parkin also promotes insolubility and aggregate formation, but in parallel, lowers hydrogen peroxide (H2O2). This thiol-based redox activity is diminished by parkin point mutants, e.g., p.C431F and p.G328E. Intriguingly, in parkin-deficient human brain H2O2 concentrations are elevated. In prkn-null mice, H2O2 levels are dysregulated under oxidative stress conditions, such as acutely by MPTP-toxin exposure or chronically due to a second genetic hit. In dopamine toxicity studies, wild-type parkin, but not disease-linked mutants, protects human dopaminergic M17 cells, in part through lowering H2O2. Parkin also neutralizes reactive, electrophilic dopamine metabolites via adduct formation, which occurs foremost at primate-specific Cys95. Further, wild-type but not p.C95A-mutant parkin augments melanin formation. In sections of normal, adult human midbrain, parkin specifically co-localizes with neuromelanin pigment, frequently within LAMP-3/CD63+ lysosomes. We conclude that oxidative modifications of parkin cysteines are associated with protective outcomes, which include the reduction of H2O2, conjugation of reactive dopamine metabolites, sequestration of radicals within insoluble aggregates, and increased melanin formation. The loss of these redox effects may augment oxidative stress in dopamine producing neurons of mutant PRKN allele carriers, thereby contributing to neurodegeneration.Competing Interest StatementDrs. B. ONuallain, M. Jin, L. Wang, P. Taylor are (or were) employees of BioLegend Inc. (Dedham, MA., USA). The Ottawa Hospital receives payments from BioLegend Inc. related to licensing agreements for immunological reagents related to parkin and α-synuclein. Dr. M. Schlossmacher received travel reimbursements from the Michael J. Fox Foundation for Parkinson Research for participation in industry summits and consulting fees as well as royalties from Genzyme-Sanofi for patents unrelated to this work. Dr. G. Toth is an employee and a shareholder of Cantabio Pharmaceuticals. Dr. A. Holmgren (deceased) served as chairman and senior scientist at IMCO Corporation Ltd AB, Stockholm, Sweden. No additional, potentially competing financial interests are declared. Dr. M. Schlossmacher received travel reimbursements from the Michael J. Fox Foundation for Parkinson Research for participation in industry summits and consulting fees as well as royalties from Genzyme-Sanofi for patents unrelated to this work. Dr. G. Toth is an employee and a shareholder of Cantabio Pharmaceuticals. Dr. A. Holmgren (deceased) served as chairman and senior scientist at IMCO Corporation Ltd AB Stockholm Sweden.