Dataset Information

Protein disaggregation by HSP101

ABSTRACT: Proteins that are vital to cell survival can become unfolded during heat stress, leading to the formation of toxic aggregates. Molecular chaperones, proteases and autophagic pathways are required to protect cells from the accumulation of protein aggregates. Small Heat Shock Proteins (sHSPs) form a first line of defense by binding to unfolding proteins to prevent irreversible protein aggregation and the complex is rapidly sequestered in stress granules during heat stress recovery. HSP101 subsequently accumulates on the surface of these insoluble foci to mediate protein disaggregation. The dynamics of this process is consistent between different cell types but indicates that protein homeostasis varies particularly between shoot and root cells. Immunoblot analysis revealed that a substantial portion of proteins present in these foci have ubiquitin moieties and protein disaggregation is necessary prior to proteasomal degradation. Co-immuno precipitation of HSP101 revealed an interaction with the 26S proteasome and localization studies revealed that HSP101 and RPN1 (Proteasome regulatory particle) initially accumulate in distinct cytosolic foci during heat stress but co-localize in the same foci during heat stress recovery which could spatiotemporal facilitate the degradation of the aggregated ubiquitinated proteins. To determine which proteins are degraded by the proteasome after disaggregation, we catalogued 620 proteins that are resolubilized by HSP101 during heat stress recovery. GO-annotation analysis revealed a significant enrichment for RNA-binding proteins, UBC13-MMS2 complex, transcription factors and ubiquitin-protein ligases. None of these proteins were preferentially targeted by the proteasome, indicating that ubiquitination occurs on a broad range of proteins and is important for the clearance of a diverse array of proteins.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell, Leaf

SUBMITTER: Fionn McLoughlin

LAB HEAD: Elizabeth Vierling

PROVIDER: PXD011483 | Pride | 2019-05-14

REPOSITORIES: Pride

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HSP101 Interacts with the Proteasome and Promotes the Clearance of Ubiquitylated Protein Aggregates.

McLoughlin Fionn F Kim Minsoo M Marshall Richard S RS Vierstra Richard D RD Vierling Elizabeth E

Plant physiology 20190521 4

Stressful environments often lead to protein unfolding and the formation of cytotoxic aggregates that can compromise cell survival. The molecular chaperone heat shock protein (HSP) 101 is a protein disaggregase that co-operates with the small HSP (sHSP) and HSP70 chaperones to facilitate removal of such aggregates and is essential for surviving severe heat stress. To better define how HSP101 protects plants, we investigated the localization and targets of this chaperone in Arabidopsis (<i>Arabid ...[more]

PMID: 31113833

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Project description:Proctor2005 - Actions of chaperones and their role in ageing This model is described in the article: Modelling the actions of chaperones and their role in ageing. Proctor CJ, Soti C, Boys RJ, Gillespie CS, Shanley DP, Wilkinson DJ, Kirkwood TB. Mech. Ageing Dev. 2005 Jan; 126(1): 119-131 Abstract: Many molecular chaperones are also known as heat shock proteins because they are synthesised in increased amounts after brief exposure of cells to elevated temperatures. They have many cellular functions and are involved in the folding of nascent proteins, the re-folding of denatured proteins, the prevention of protein aggregation, and assisting the targeting of proteins for degradation by the proteasome and lysosomes. They also have a role in apoptosis and are involved in modulating signals for immune and inflammatory responses. Stress-induced transcription of heat shock proteins requires the activation of heat shock factor (HSF). Under normal conditions, HSF is bound to heat shock proteins resulting in feedback repression. During stress, cellular proteins undergo denaturation and sequester heat shock proteins bound to HSF, which is then able to become transcriptionally active. The induction of heat shock proteins is impaired with age and there is also a decline in chaperone function. Aberrant/damaged proteins accumulate with age and are implicated in several important age-related conditions (e.g. Alzheimer's disease, Parkinson's disease, and cataract). Therefore, the balance between damaged proteins and available free chaperones may be greatly disturbed during ageing. We have developed a mathematical model to describe the heat shock system. The aim of the model is two-fold: to explore the heat shock system and its implications in ageing; and to demonstrate how to build a model of a biological system using our simulation system (biology of ageing e-science integration and simulation (BASIS)). This model is hosted on BioModels Database and identified by: BIOMD0000000091. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:The expression of heat-shock proteins (Hsps) induced by a non-lethal heat treatment confers acquired thermotolerance (AT) to organisms against a subsequent challenge of otherwise lethal temperature. After stress signal lifted, AT gradually decayed with the decline of Hsps during recovery period. The duration of AT may be critical for sessile organisms, such as plants, to survive repeated heat stress in the environment. To identify heat-induced genes involved in duration of AT, we took a reverse-genetics approach by screening for Arabidopsis T-DNA insertion mutants that show decreased thermotolerance after a long recovery at non-stress condition following a conditioning treatment. Among the tested mutants corresponding to 47 genes, only the HsfA2 knockout mutant showed significant phenotype. The mutant plants were more sensitive to severe heat stress than the wild type after long but not short recovery following a pretreatment at 37oC, which can be complemented by introducing a wild-type copy of the gene. Quantitative hypocotyl elongation assay also revealed that AT decayed faster in the absence of HsfA2. Significant decline of the transcript levels of several highly heat-induced genes was observed in the HsfA2 knockout plants after a 4-h recovery or after 2 h of prolonged heat stress. Immunoblot anlysis showed that Hsa32 and class I small Hsp were lower in the mutant than in the wild type after a long recovery. Our results suggest that HsfA2 as a heat-induced transactivator sustains the post-stress expression of Hsp genes and extends the duration of AT in Arabidopsis. Experiment Overall Design: Total RNA was isolated from the seedlings of 5-d old wild-type and HsfA2 knockout mutant seedlings (a pool of about 100 plants per treatment in duplicates) harvested immediately after heat shock treatment. In this experiment, total 12 chips were used, 1 each for 2 biological replicates of the control and HS-treated samples for the wild type and mutant plants.

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