Bjorkoy G, Lamark T, Brech A, Outzen H, Perander M, Overvatn A et al.. p62/SQSTM1 forms protein aggregates degraded by autophagy and has a protective effect on huntingtin-induced cell death. J Cell Biol 171: 603-614

Biochemistry Department, Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway.
The Journal of Cell Biology (Impact Factor: 9.83). 12/2005; 171(4):603-14. DOI: 10.1083/jcb.200507002
Source: PubMed


Autophagic degradation of ubiquitinated protein aggregates is important for cell survival, but it is not known how the autophagic machinery recognizes such aggregates. In this study, we report that polymerization of the polyubiquitin-binding protein p62/SQSTM1 yields protein bodies that either reside free in the cytosol and nucleus or occur within autophagosomes and lysosomal structures. Inhibition of autophagy led to an increase in the size and number of p62 bodies and p62 protein levels. The autophagic marker light chain 3 (LC3) colocalized with p62 bodies and co-immunoprecipitated with p62, suggesting that these two proteins participate in the same complexes. The depletion of p62 inhibited recruitment of LC3 to autophagosomes under starvation conditions. Strikingly, p62 and LC3 formed a shell surrounding aggregates of mutant huntingtin. Reduction of p62 protein levels or interference with p62 function significantly increased cell death that was induced by the expression of mutant huntingtin. We suggest that p62 may, via LC3, be involved in linking polyubiquitinated protein aggregates to the autophagy machinery.

Download full-text


Available from: Harald Stenmark,

Click to see the full-text of:

Article: Bjorkoy G, Lamark T, Brech A, Outzen H, Perander M, Overvatn A et al.. p62/SQSTM1 forms protein aggregates degraded by autophagy and has a protective effect on huntingtin-induced cell death. J Cell Biol 171: 603-614

5.79 MB

See full-text
  • Source
    • " in the LC3 lipidation reaction ( Hanada et al . , 2007 ) . In addition to components directly involved in the autophagic process , markers of autophagic activity have also been identified . Sequestosome 1 ( p62 / SQSTM1 ) binds to Atg8 / LC3 and disruptions in autophagy have been found to be associated with higher p62 / SQSTM1 expression levels ( Bjorkoy et al . , 2005 ; Wang et al . , 2006 ; Komatsu et al . , 2007b ; Pankiv et al . , 2007 ) , while higher lysosomal - associated membrane protein 1 ( LAMP1 ) can indicate the presence of more lysosomes and autophagosomes during rises in autophagic activity ( Klionsky et al . , 2008 ) . While cellular differences resulting from prolonged HIV infection can"
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the role of autophagy in HIV-infected subjects with neurocognitive impairment (NCI) ± HIV encephalitis (HIVE), many of which had a history of polysubstance abuse/dependence, using post-mortem brain tissues to determine whether differences in autophagy related factors may be more associated with NCI or NCI-encephalitis. Using qRT-PCR, we detected significant differences in gene expression levels with SQSTM1, LAMP1 higher in HIV-infected subjects without NCI while ATG5, SQSTM1 were then lower in HIV infection/NCI and ATG7, SQSTM1 being higher in NCI-HIVE. Immunohistochemical labeling of these autophagy associated proteins (also including Beclin 1 and LC3B) in Iba1-positive microglial cells showed generally higher immunoreactivity in the NCI and NCI-HIVE groups with more focal vs. diffuse patterns of expression in the NCI-HIVE group. Furthermore, analysis of microarray data from these same subjects found significantly higher levels of LAMP1 in NCI-HIVE compared to uninfected subjects in the basal ganglia. Finally, we tested the effect of supernatant from HIV-1-infected microglia and HIV-1 Tat protein in combination with morphine on neurons in vitro and found opposing events with both significant inhibition of autophagic flux and reduced dendrite length for morphine and supernatant treatment while Tat and morphine exposure resulted in lower autophagic activity at an earlier time point and higher levels in the later. These results suggest autophagy genes and their corresponding proteins may be differentially regulated at the transcriptional, translational, and post-translational levels in the brain during various stages of the HIV disease and that infected individuals exposed to morphine can experience mixed signaling of autophagic activity which could lead to more severe NCI than those without opioid use.
    Frontiers in Microbiology 07/2015; 6:653. DOI:10.3389/fmicb.2015.00653 · 3.99 Impact Factor
  • Source
    • "At the current state of research, it is also possible to envision that at low concentrations poly-ubiquitin chains actively crosslink p62 filaments (Morimoto et al., 2015), whereas at molar excess poly-ubiquitin chains disassemble p62 filaments. Moreover , membrane-enwrapped p62 bodies can also enter the autophagosomal pathway without enclosing additional cytoplasmic material to be degraded (Bjørkøy et al., 2005). Thus, p62 bodies will have a cytoprotective function to target misfolded cytotoxic proteins for degradation, as p62 sequesters them and prevents their interference with basic cellular functions. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The scaffold protein p62/SQSTM1 is involved in protein turnover and signaling and is commonly found in dense protein bodies in eukaryotic cells. In autophagy, p62 acts as a selective autophagy receptor that recognizes and shuttles ubiquitinated proteins to the autophagosome for degradation. The structural organization of p62 in cellular bodies and the interplay of these assemblies with ubiquitin and the autophagic marker LC3 remain to be elucidated. Here, we present a cryo-EM structural analysis of p62. Together with structures of assemblies from the PB1 domain, we show that p62 is organized in flexible polymers with the PB1 domain constituting a helical scaffold. Filamentous p62 is capable of binding LC3 and addition of long ubiquitin chains induces disassembly and shortening of filaments. These studies explain how p62 assemblies provide a large molecular scaffold for the nascent autophagosome and reveal how they can bind ubiquitinated cargo. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Cell Reports 04/2015; 11(5). DOI:10.1016/j.celrep.2015.03.062 · 8.36 Impact Factor
  • Source
    • "This activity relies on receptors that bind to cargo and Atg8 (LC3) present at autophagosomal membranes via LC3-interacting regions (LIR) [76], causing engulfment of bound substrates by the autophagic membrane. In mammalian cells, the receptors p62 and Nbr1 target ubiquitinated protein inclusions (ALIS/DALIS) [77] and aggregates of polyQ-proteins [78] for a specific form of selective autophagy, termed aggrephagy [79]. In yeast, the adaptor protein Cue5 has recently been identified by Jentsch and coworkers [75], that is A C C E P T E D M A N U S C R I P T "
    [Show abstract] [Hide abstract]
    ABSTRACT: An evolutionary conserved response of cells to proteotoxic stress is the organized sequestration of misfolded proteins into subcellular deposition sites. In Saccharomyces cerevisiae three major sequestration sites for misfolded proteins exist, IPOD, INQ (former JUNQ) and CytoQ. IPOD is perivacuolar and predominantly sequesters amyloidogenic proteins. INQ and CytoQs are stress-induced deposits for misfolded proteins residing in the nucleus and the cytosol, respectively, and requiring cell compartment-specific aggregases, nuclear Btn2 and cytosolic Hsp42, for formation. The organized aggregation of misfolded proteins is proposed to serve several purposes collectively increasing cellular fitness and survival under proteotoxic stress. These include (i) shielding of cellular processes from interference by toxic protein conformers; (ii) reducing the substrate burden for protein quality control systems upon immediate stress; (iii) orchestrating chaperone and protease functions for efficient repair or degradation of damaged proteins; this involves initial extraction of aggregated molecules via the Hsp70/Hsp104 bi-chaperone system followed by either refolding or proteasomal degradation or removal of entire aggregates by selective autophagy (aggrephagy) involving the adaptor protein Cue5; (iv) enabling asymmetric retention of protein aggregates during cell division, thereby allowing for damage clearance in daughter cells. Regulated protein aggregation thus serves cytoprotective functions vital for the maintenance of cell integrity and survival even under adverse stress conditions and during aging.
    Journal of Molecular Biology 02/2015; 76(7). DOI:10.1016/j.jmb.2015.02.006 · 4.33 Impact Factor
Show more