Dopamine- and zinc-induced autophagosome formation facilitates PC12 cell survival

• Published in: Cell biology and toxicology 2013-12, Vol.29 (6), p.415-429
• Main Authors: Hung, Hui-Hsing, Huang, Wei-Pang, Pan, Chien-Yuan
• Format: Article
• Language: English
• Subjects: Aggregates; Animals; Apoptosis; Apoptosis - drug effects; Autophagy; Autophagy - drug effects; Biochemistry; Biomedical and Life Sciences; Cations; Cell Biology; Cell Line, Tumor; Cell Survival - drug effects; Cells; Chromones - pharmacology; Dopamine; Dopamine - pharmacology; Green Fluorescent Proteins; Life Sciences; Morpholines - pharmacology; Mortality; Neurons - drug effects; Original Research; PC12 Cells; Phagosomes - drug effects; Pharmacology/Toxicology; Phosphatidylinositol Phosphates - metabolism; Rats; RNA, Small Interfering; Signal Transduction - drug effects; Zinc; Zinc - pharmacology
• ISSN: 0742-2091; 1573-6822
• DOI: 10.1007/s10565-013-9261-2

Dopamine oxidation and divalent cations have been reported to induce neuronal cell death. Although autophagy is involved in neuronal cell death, it has also been suggested to facilitate cell survival. We sought to investigate the role of autophagy in PC12 cells and cultured neurons treated with dopamine and Zn 2+ . Cells expressing EGFP-LC3 were treated with high concentrations of dopamine and Zn 2+ , and the formation of EGFP-LC3 fluorescence aggregates was monitored. Our results showed a significant increase in the number of fluorescent puncta in the cytosol of PC12 cells treated with these chemicals. These treatments enhanced LC3 lipidation levels in PC12 cells. Decreasing the ATG7 protein level using specific small interference RNA (siRNA) and pretreating with phosphatidylinositol 3-phosphate kinase blockers, wortmannin and LY294002, inhibited puncta formation. Dopamine or Zn 2+ treatment significantly elevated the intracellular Zn 2+ concentration ([Zn 2+ ] i ); however, inhibiting the [Zn 2+ ] i elevation in dopamine-treated cells suppressed the puncta formation. LY294002 or siRNA-directed members of the autophagy pathway increased the fraction of phosphatidylserine present on the outer membrane leaflet in PC12 cells treated with dopamine or Zn 2+ , suggesting an increase in apoptosis. Primary embryonic midbrain neurons expressing EGFP-LC3 also displayed a significant increase in the number of fluorescent aggregates in cells upon treatment with dopamine or Zn 2+ . Dopamine or Zn 2+ treatment significantly elevated the [Zn 2+ ] i in neurons and caused neuronal death. Our results indicate that treating cells with dopamine and Zn 2+ results in the activation of the autophagy pathway in an effort to enhance cell survival.