title: Enhanced epithelial-to-mesenchymal transition associated with lysosome dysfunction in podocytes: role of p62/Sequestosome 1 as a signaling hub.
abstract: BACKGROUND
  Autophagy is of importance in the regulation of cell differentiation and senescence in podocytes. It is possible that derangement of autophagy under different pathological conditions activates or enhances Epithelial-to-Mesenchymal Transition (EMT) in podocytes, resulting in glomerular sclerosis. To test this hypothesis, the present study produced lysosome dysfunction by inhibition of the vacuolar H(+)-ATPase (V-ATPase) to test whether deficiency of autophagic flux leads to enhancement of EMT in podocytes.
  
  
  RESULTS
  By Western blot and confocal analysis, lysosome inhibition using a V-ATPase inhibitor or its siRNA was found to markedly decreases the epithelial markers (P-cadherin and ZO-1) and increases the mesenchymal markers (FSP-1 and α-SMA). This enhancement was accompanied by deficient autophagic flux, as demonstrated by marked increases in LC3B-II and p62/Sequestosome 1. However, inhibition of autophagosome formation using spaudin-1 significantly attenuated both enhancement of EMT and deficiency of autophagic flux. To explore the mechanisms by which deficient autophagic flux enhances EMT, we tested the role of accumulated p62 as a signal hub in this process. Neither the nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear kappa-light-chain-enhancer pathways of p62 contributed to enhanced EMT. However, inhibition of cyclin-dependent kinase 1 (CDK1) activity reduced the phosphorylation of p62 and enhanced EMT in podocytes similar to lysosome dysfunction.
  
  
  CONCLUSIONS
  The lack of phosphorylated p62 leads to a faster exit from cell mitosis, enhanced EMT associated with lysosome dysfunction may be attributed to accumulation of p62 and associated reduction of p62 phosphorylation.
authors.affiliation: Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Guangbi
authors.initials: G
authors.lastname: Li
authors.forename: Cai-Xia
authors.initials: CX
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Xia
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Ritter
authors.forename: Todd W B
authors.initials: TW
authors.lastname: Gehr
authors.forename: Krishna
authors.initials: K
authors.lastname: Boini
authors.forename: Pin-Lan
authors.initials: PL
authors.lastname: Li
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D018613:Microscopy, Confocal; D008938:Mitosis; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D050199:Podocytes / Q000166:cytology / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D015398:Signal Transduction / Q000187:drug effects; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein / Q000378:metabolism
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; D018942:Macrolides; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495635:NFE2L2 protein, human; D034741:RNA, Small Interfering; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; C057620:bafilomycin A; D016203:CDC2 Protein Kinase; D025262:Vacuolar Proton-Translocating ATPases
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