title: Activation of the Keap1/Nrf2 stress response pathway in autophagic vacuolar myopathies.
abstract: Nrf2 (nuclear factor [erythroid-d﻿erived 2]-like 2﻿;﻿ the transcriptional master regulator of the antioxidant stress response) is regulated through interaction with its cytoplasmic inhibitor Keap1 (Kelch-like ECH-associated protein 1), which under basal conditions targets Nrf2 for proteasomal degradation. Sequestosome 1﻿ ﻿(SQSTM1)/p62-a multifunctional adapter protein that accumulates following autophagy inhibition and can serve as a diagnostic marker for human autophagic vacuolar myopathies (AVMs)-was recently shown to compete with Nrf2 for Keap1 binding, resulting in activation of the Nrf2 pathway. In this study, we used 55 human muscle biopsies divided into five groups [normal control, hydroxychloroquine- or colchicine-treated non-AVM control, hydroxychloroquine- or colchicine-induced toxic AVM, polymyositis, and inclusion body myositis (IBM)] to evaluate whether Keap1-SQSTM1 interaction led to increased Nrf2 signaling in human AVMs. In toxic AVMs and IBM, but not in control muscle groups or polymyositis, Keap1 antibody labeled sarcoplasmic protein aggregates that can be used as an alternate diagnostic marker for both AVM types; these Keap1-positive aggregates were co-labeled with the antibody against SQSTM1 but not with the antibody against autophagosome marker LC3 (microtubule-associated protein 1 light chain 3). In human AVM muscle, sequestration of Keap1 into the SQSTM1-positive protein aggregates was accompanied by an increase in mRNA and protein levels of Nrf2 target genes; similarly, treatment of differentiated C2C12 myotubes with autophagy inhibitor chloroquine led to an increase in the nuclear Nrf2 protein level and an increase in expression of the Nrf2-regulated genes. Taken together, our findings demonstrate that Nrf2 signaling is upregulated in autophagic muscle disorders and raise the possibility that autophagy disruption in skeletal muscle leads to dysregulation of cellular redox homeostasis.
authors: School of Medicine, University of California, San Francisco, CA, USA.
authors: Steve
authors: S
authors: Duleh
authors: Department of Pathology, University of California, San Francisco, CA, USA.
authors: Xianhong
authors: X
authors: Wang
authors: School of Pharmacy, University of California, San Francisco, CA, USA.
authors: Allison
authors: A
authors: Komirenko
authors: Department of Pathology, University of California, San Francisco, CA, USA. Marta.Margeta@ucsf.edu.
authors: Marta
authors: 0000-0001-6889-2488
authors: M
authors: Margeta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D015331:Cohort Studies; D005260:Female; D006801:Humans; D000072019:Kelch-Like ECH-Associated Protein 1 / Q000378:metabolism*; D016464:Lysosomal Storage Diseases / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009135:Muscular Diseases / Q000378:metabolism* / Q000473:pathology; D018979:Myositis, Inclusion Body / Q000378:metabolism / Q000473:pathology; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D066263:Protein Aggregation, Pathological / Q000378:metabolism / Q000473:pathology; D000071456:Sequestosome-1 Protein / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D055815:Young Adult
chemical_list: C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein
keywords: Autophagy; Colchicine; Hydroxychloroquine; Inclusion body myositis; Keap1; Nrf2; Stress response signaling; Toxic myopathy; Vacuolar myopathy