PMID- 25062253 OWN - NLM STAT- MEDLINE DCOM- 20151116 LR - 20231213 IS - 1932-6203 (Electronic) IS - 1932-6203 (Linking) VI - 9 IP - 7 DP - 2014 TI - Proteasome inhibitors activate autophagy involving inhibition of PI3K-Akt-mTOR pathway as an anti-oxidation defense in human RPE cells. PG - e103364 LID - 10.1371/journal.pone.0103364 [doi] LID - e103364 AB - The two major intracellular protein degradation systems, the ubiquitin-proteasome system (UPS) and autophagy, work collaboratively in many biological processes including development, apoptosis, aging, and countering oxidative injuries. We report here that, in human retinal pigment epithelial cells (RPE), ARPE-19 cells, proteasome inhibitors, clasto-lactacystinbeta-lactone (LA) or epoxomicin (Epo), at non-lethal doses, increased the protein levels of autophagy-specific genes Atg5 and Atg7 and enhanced the conversion of microtubule-associated protein light chain (LC3) from LC3-I to its lipidative form, LC3-II, which was enhanced by co-addition of the saturated concentration of Bafilomycin A1 (Baf). Detection of co-localization for LC3 staining and labeled-lysosome further confirmed autophagic flux induced by LA or Epo. LA or Epo reduced the phosphorylation of the protein kinase B (Akt), a downstream target of phosphatidylinositol-3-kinases (PI3K), and mammalian target of rapamycin (mTOR) in ARPE-19 cells; by contrast, the induced changes of autophagy substrate, p62, showed biphasic pattern. The autophagy inhibitor, Baf, attenuated the reduction in oxidative injury conferred by treatment with low doses of LA and Epo in ARPE-19 cells exposed to menadione (VK3) or 4-hydroxynonenal (4-HNE). Knockdown of Atg7 with siRNA in ARPE-19 cells reduced the protective effects of LA or Epo against VK3. Overall, our results suggest that treatment with low levels of proteasome inhibitors confers resistance to oxidative injury by a pathway involving inhibition of the PI3K-Akt-mTOR pathway and activation of autophagy. FAU - Tang, Bingrong AU - Tang B AD - School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, P.R. China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang Province, P.R. China. FAU - Cai, Jingjing AU - Cai J AD - School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, P.R. China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang Province, P.R. China. FAU - Sun, Lin AU - Sun L AD - School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, P.R. China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang Province, P.R. China. FAU - Li, Yiping AU - Li Y AD - Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, P.R. China. FAU - Qu, Jia AU - Qu J AD - School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, P.R. China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang Province, P.R. China. FAU - Snider, Barbara Joy AU - Snider BJ AD - Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, United States of America. FAU - Wu, Shengzhou AU - Wu S AD - School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, P.R. China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang Province, P.R. China. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20140725 PL - United States TA - PLoS One JT - PloS one JID - 101285081 RN - 0 (ATG5 protein, human) RN - 0 (Autophagy-Related Protein 5) RN - 0 (Microtubule-Associated Proteins) RN - 0 (Proteasome Inhibitors) RN - EC 2.7.11.1 (Proto-Oncogene Proteins c-akt) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 6.2.1.45 (ATG7 protein, human) RN - EC 6.2.1.45 (Autophagy-Related Protein 7) RN - EC 6.2.1.45 (Ubiquitin-Activating Enzymes) SB - IM MH - *Autophagy MH - Autophagy-Related Protein 5 MH - Autophagy-Related Protein 7 MH - Cell Line MH - Humans MH - Microtubule-Associated Proteins/genetics/metabolism MH - *Oxidative Stress MH - Phosphatidylinositol 3-Kinases/*metabolism MH - Proteasome Inhibitors/*pharmacology MH - Proto-Oncogene Proteins c-akt/*metabolism MH - Retinal Pigment Epithelium/drug effects/*metabolism MH - Signal Transduction MH - TOR Serine-Threonine Kinases/*metabolism MH - Ubiquitin-Activating Enzymes/genetics/metabolism PMC - PMC4111584 COIS- Competing Interests: The authors have declared that no competing interests exist. EDAT- 2014/07/26 06:00 MHDA- 2015/11/17 06:00 PMCR- 2014/07/25 CRDT- 2014/07/26 06:00 PHST- 2013/09/20 00:00 [received] PHST- 2014/07/01 00:00 [accepted] PHST- 2014/07/26 06:00 [entrez] PHST- 2014/07/26 06:00 [pubmed] PHST- 2015/11/17 06:00 [medline] PHST- 2014/07/25 00:00 [pmc-release] AID - PONE-D-13-38903 [pii] AID - 10.1371/journal.pone.0103364 [doi] PST - epublish SO - PLoS One. 2014 Jul 25;9(7):e103364. doi: 10.1371/journal.pone.0103364. eCollection 2014.