title: Bioenergetics of neurons inhibit the translocation response of Parkin following rapid mitochondrial depolarization.
abstract: Recent studies delineate a pathway involving familial Parkinson's disease (PD)-related proteins PINK1 and Parkin, in which PINK1-dependent mitochondrial accumulation of Parkin targets depolarized mitochondria towards degradation through mitophagy. The pathway has been primarily characterized in cells less dependent on mitochondria for energy production than neurons. Here we report that in neurons, unlike other cells, mitochondrial depolarization by carbonyl cyanide m-chlorophenyl hydrazone did not induce Parkin translocation to mitochondria or mitophagy. PINK1 overexpression increased basal Parkin accumulation on neuronal mitochondria, but did not sensitize them to depolarization-induced Parkin translocation. Our data suggest that bioenergetic differences between neurons and cultured cell lines contribute to these different responses. In HeLa cells utilizing usual glycolytic metabolism, mitochondrial depolarization robustly triggered Parkin-mitochondrial translocation, but this did not occur in HeLa cells forced into dependence on mitochondrial respiration. Declining ATP levels after mitochondrial depolarization correlated with the absence of induced Parkin-mitochondrial translocation in both HeLa cells and neurons. However, intervention allowing neurons to maintain ATP levels after mitochondrial depolarization only modestly increased Parkin recruitment to mitochondria, without evidence of increased mitophagy. These data suggest that changes in ATP levels are not the sole determinant of the different responses between neurons and other cell types, and imply that additional mechanisms regulate mitophagy in neurons. Since the Parkin-mitophagy pathway is heavily dependent on bioenergetic status, the unique metabolic properties of neurons likely influence the function of this pathway in the pathogenesis of PD.
authors.affiliation: Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Victor S
authors.initials: VS
authors.lastname: Van Laar
authors.forename: Beth
authors.initials: B
authors.lastname: Arnold
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Cassady
authors.forename: Charleen T
authors.initials: CT
authors.lastname: Chu
authors.forename: Edward A
authors.initials: EA
authors.lastname: Burton
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Berman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D015536:Down-Regulation; D004734:Energy Metabolism; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D000099202:PTEN-Induced Putative Kinase
chemical_list: D000255:Adenosine Triphosphate; D011494:Protein Kinases; D044767:Ubiquitin-Protein Ligases; D000099202:PTEN-Induced Putative Kinase; C111567:parkin protein