cells Review Interaction between Parkin and a-Synuclein in PARK2-Mediated Parkinson’s Disease Daniel Aghaie Madsen 1, Sissel Ida Schmidt 1, Morten Blaabjerg 1,2,3,4 and Morten Meyer 1,2,3,4,* 1 Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, 5000 Odense, Denmark;
[email protected] (D.A.M.);
[email protected] (S.I.S.);
[email protected] (M.B.) 2 Department of Neurology, Odense University Hospital, 5000 Odense, Denmark 3 Department of Clinical Research, University of Southern Denmark, 5000 Odense, Denmark 4 BRIDGE—Brain Research Inter-Disciplinary Guided Excellence, Department of Clinical Research, University of Southern Denmark, 5000 Odense, Denmark * Correspondence:
[email protected]; Tel.: +45-65503802 Abstract: Parkin and a-synuclein are two key proteins involved in the pathophysiology of Parkinson’s disease (PD). Neurotoxic alterations of a-synuclein that lead to the formation of toxic oligomers and fibrils contribute to PD through synaptic dysfunction, mitochondrial impairment, defective endoplasmic reticulum and Golgi function, and nuclear dysfunction. In half of the cases, the recessively inherited early-onset PD is caused by loss of function mutations in the PARK2 gene that encodes the E3-ubiquitin ligase, parkin. Parkin is involved in the clearance of misfolded and aggregated proteins by the ubiquitin-proteasome system and regulates mitophagy and mitochondrial biogenesis. PARK2-related PD is generally thought not to be associated with Lewy body formation although it is a neuropathological hallmark of PD. In this review article, we provide an overview of post-mortem neuropathological examinations of PARK2 patients and present the current knowledge of a functional interaction between parkin and a-synuclein in the regulation of protein aggregates including Lewy bodies.