“Proteotoxicity” of ATP Depletion: Disruption of the Cytoskeleton, Protein Aggregation and Involvement of Molecular Chaperones

1997 ◽  
pp. 49-83 ◽  
Author(s):  
Alexander E. Kabakov ◽  
Vladimir L. Gabai
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Atp Depletion ◽  
Cytoskeleton Protein

scholarly journals Molecular chaperones antagonize proteotoxicity by differentially modulating protein aggregation pathways

Prion ◽  
2009 ◽  
Vol 3 (2) ◽  
pp. 51-58 ◽  
Author(s):  
Peter M. Douglas ◽  
Daniel W. Summers ◽  
Douglas M. Cyr
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones

scholarly journals The Hsp70/Hsp90 Co-Chaperone Hop/Stip1 Shifts the Proteostatic Balance from Folding Towards Degradation

2019 ◽  
Author(s):  
Kaushik Bhattacharya ◽  
Lorenz Weidenauer ◽  
Tania Morán Luengo ◽  
Pablo C. Echeverría ◽  
Lilia Bernasconi ◽  
...  
Keyword(s):  
Protein Folding ◽  
Protein Aggregation ◽  
Human Cell ◽  
Molecular Chaperones ◽  
Human Cell Lines ◽  
Specific Function ◽  
Core Particle ◽  
Knock Out ◽  
The Core

SUMMARYHop/Stip1/Sti1 is thought to be essential as a co-chaperone to facilitate substrate transfer between the Hsp70 and Hsp90 molecular chaperones. Despite this proposed key function for protein folding and maturation, it is not essential in a number of eukaryotes and bacteria lack an ortholog. We set out to identify and to characterize its eukaryote-specific function. Human cell lines and the budding yeast with deletions of the Hop/Sti1 gene display reduced proteasome activity due to inefficient capping of the core particle with regulatory particles. Unexpectedly, knock-out cells are more proficient at preventing protein aggregation and at promoting protein refolding. Without the restraint by Hop, a more efficient folding activity of the prokaryote-like Hsp70/Hsp90 complex, which can also be demonstrated in vitro, compensates for the proteasomal defect and ensures an alternate proteostatic equilibrium. Thus, cells may act on Hop to shift the proteostatic balance between folding and degradation.

scholarly journals Suppression of aggregate and amyloid formation by a novel intrinsically disordered region in metazoan Hsp110 chaperones

2021 ◽  
Author(s):  
Unekwu M. Yakubu ◽  
Kevin A. Morano
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Citrate Synthase ◽  
Neuronal Cell ◽  
Amyloid Formation ◽  
Nucleotide Exchange ◽  
Aggregation Assay ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Region

AbstractMolecular chaperones maintain protein homeostasis (proteostasis) by ensuring the proper folding of polypeptides. Loss of proteostasis has been linked to the onset of numerous neurodegenerative disorders including Alzheimer’s, Parkinson’s, and Huntington’s disease. Hsp110 is related to the canonical Hsp70 class of protein folding molecular chaperones and interacts with Hsp70 as a nucleotide exchange factor (NEF), promoting rapid cycling of ADP for ATP. In addition to its NEF activity, Hsp110 possesses an Hsp70-like substrate binding domain (SBD) whose biological roles remain undefined. Previous work in Drosophila melanogaster has shown that loss of the sole Hsp110 gene (Hsc70cb) accelerates the aggregation of polyglutamine (polyQ)-expanded human Huntingtin, while its overexpression protects against polyQ-mediated neuronal cell death. We hypothesize that in addition to its role as an Hsp70 NEF, Drosophila Hsp110 may function in the fly as a protective protein “holdase”, preventing the aggregation of unfolded polypeptides via the SBD-β subdomain. Using an in vitro protein aggregation assay we demonstrate for the first time that Drosophila Hsp110 effectively prevents aggregation of the model substrate citrate synthase. We also report the discovery of a redundant and heretofore unknown potent holdase capacity in a 138 amino-acid region of Hsp110 carboxyl-terminal to both SBD-β and SBD-α (henceforth called the C-terminal extension). This sequence is highly conserved in metazoan Hsp110 genes, completely absent from fungal representatives, including Saccharomyces cerevisiae SSE1, and is computationally predicted to contain an intrinsically disordered region (IDR). We demonstrate that this IDR sequence within the human Hsp110s, Apg-1 and Hsp105α, inhibits the formation of amyloid Aβ-42 and α-synuclein fibrils in vitro but cannot mediate fibril disassembly. Together these findings demonstrate the existence of a second independent, passive holdase property of metazoan Hsp110 chaperones capable of suppressing both general protein aggregation and amyloidogenesis and raise the possibility of exploitation of this IDR for therapeutic benefit in combating neurodegenerative disease.

scholarly journals The Link That Binds: The Linker of Hsp70 as a Helm of the Protein’s Function

Biomolecules ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 543 ◽  
Author(s):  
Chakafana ◽  
Zininga ◽  
Shonhai
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Atp Hydrolysis ◽  
Sequence Data ◽  
Substrate Binding ◽  
Binding Domain ◽  
Nucleotide Exchange ◽  
Hsp70 Family ◽  
Nucleotide Exchange Factors ◽  
Functional Features

The heat shock 70 (Hsp70) family of molecular chaperones plays a central role in maintaining cellular proteostasis. Structurally, Hsp70s are composed of an N-terminal nucleotide binding domain (NBD) which exhibits ATPase activity, and a C-terminal substrate binding domain (SBD). The binding of ATP at the NBD and its subsequent hydrolysis influences the substrate binding affinity of the SBD through allostery. Similarly, peptide binding at the C-terminal SBD stimulates ATP hydrolysis by the N-terminal NBD. Interdomain communication between the NBD and SBD is facilitated by a conserved linker segment. Hsp70s form two main subgroups. Canonical Hsp70 members generally suppress protein aggregation and are also capable of refolding misfolded proteins. Hsp110 members are characterized by an extended lid segment and their function tends to be largely restricted to suppression of protein aggregation. In addition, the latter serve as nucleotide exchange factors (NEFs) of canonical Hsp70s. The linker of the Hsp110 family is less conserved compared to that of the canonical Hsp70 group. In addition, the linker plays a crucial role in defining the functional features of these two groups of Hsp70. Generally, the linker of Hsp70 is quite small and varies in size from seven to thirteen residues. Due to its small size, any sequence variation that Hsp70 exhibits in this motif has a major and unique influence on the function of the protein. Based on sequence data, we observed that canonical Hsp70s possess a linker that is distinct from similar segments present in Hsp110 proteins. In addition, Hsp110 linker motifs from various genera are distinct suggesting that their unique features regulate the flexibility with which the NBD and SBD of these proteins communicate via allostery. The Hsp70 linker modulates various structure-function features of Hsp70 such as its global conformation, affinity for peptide substrate and interaction with co-chaperones. The current review discusses how the unique features of the Hsp70 linker accounts for the functional specialization of this group of molecular chaperones.

scholarly journals Proteinaceous Infectious Behavior in Non-pathogenic Proteins Is Controlled by Molecular Chaperones

2002 ◽  
Vol 277 (51) ◽  
pp. 49422-49427 ◽  
Author(s):  
Anat Peres Ben-Zvi ◽  
Pierre Goloubinoff
Keyword(s):  
Heat Stress ◽  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Polypeptide Chain ◽  
Protein Aggregates ◽  
Single Polypeptide Chain ◽  
Activity Measurements ◽  
Associated Proteins ◽  
External Stresses ◽  
Single Polypeptide

External stresses or mutations may cause labile proteins to lose their distinct native conformations and seek alternatively stable aggregated forms. Molecular chaperones that specifically act on protein aggregates were used here as a tool to address the biochemical nature of stable homo- and hetero-aggregates from non-pathogenic proteins formed by heat-stress. Confirmed by sedimentation and activity measurements, chaperones demonstrated that a single polypeptide chain can form different species of aggregates, depending on the denaturing conditions. Indicative of a cascade reaction, sub-stoichiometric amounts of one fast-aggregating protein strongly accelerated the conversion of another soluble, slow-aggregating protein into insoluble, chaperone-resistant aggregates. Chaperones strongly inhibited seed-induced protein aggregation, suggesting that they can prevent and cure proteinaceous infectious behavior in homo- and hetero-aggregates from common and disease-associated proteins in the cell.

Crowbars and ratchets: Hsp100 chaperones as tools in reversing protein aggregation

2001 ◽  
Vol 79 (5) ◽  
pp. 557-568 ◽  
Author(s):  
John R Glover ◽  
John M Tkach
Keyword(s):  
Protein Synthesis ◽  
Protein Aggregation ◽  
Molecular Chaperone ◽  
Molecular Chaperones ◽  
Recent Progress ◽  
Chemical Stress ◽  
Intracellular Aggregates ◽  
Physical And Chemical ◽  
Hsp100 Chaperones

Molecular chaperones have the capacity to prevent inappropriate interactions between aggregation-prone folding or unfolding intermediates created in the cell during protein synthesis or in response to physical and chemical stress. What happens when surveillance by molecular chaperones is evaded or overwhelmed and aggregates accumulate? Recent progress in the elucidation of Hsp100/Clp function suggests that intracellular aggregates or stable complexes can be progressively dissolved by the action of chaperones that act as molecular crowbars or ratchets. These insights set the stage for new progress in the understanding and treatment of diseases of protein folding.Key words: molecular chaperone, Hsp100, aggregation, amyloid.

scholarly journals Molecular chaperones as modulators of polyglutamine protein aggregation and toxicity

2002 ◽  
Vol 99 (Supplement 4) ◽  
pp. 16412-16418 ◽  
Author(s):  
H. Sakahira ◽  
P. Breuer ◽  
M. K. Hayer-Hartl ◽  
F. U. Hartl
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Polyglutamine Protein

Pretreatment with inducers of ER molecular chaperones protects epithelial cells subjected to ATP depletion

1999 ◽  
Vol 277 (2) ◽  
pp. F211-F218 ◽  
Author(s):  
Kevin T. Bush ◽  
Sathish K. George ◽  
Ping L. Zhang ◽  
Sanjay K. Nigam
Keyword(s):  
Molecular Chaperones ◽  
Cell Injury ◽  
Cell Model ◽  
Mdck Cells ◽  
Cell Damage ◽  
Protein Translation ◽  
Atp Depletion ◽  
Cysteine Protease Inhibitor ◽  
Cytoprotective Effect ◽  
Trypan Blue Exclusion

We have investigated the potential cytoprotective role of endoplasmic reticulum (ER) molecular chaperones in a cultured cell model of renal ischemia. Madin-Darby canine kidney (MDCK) cells were pretreated with tunicamycin (an inducer of ER but not cytosolic molecular chaperones) for 12–16 h, followed by 6 h of ATP depletion. A rapid and severe depletion of cellular ATP was noted in both control and tunicamycin-treated cells. Trypan blue exclusion assays indicated that pretreatment of MDCK cells with tunicamycin reduced ATP depletion-induced cell damage by ∼80% compared with nonpretreated controls. This apparent cytoprotective effect was also found following pretreatment with another inducer of ER molecular chaperones (i.e., A23187). For example, A23187 was found to reduce lactate dehydrogenase release by ∼50% compared with untreated controls, whereas E-64, a cysteine protease inhibitor which may affect degradation of some proteins in the ER, had little or no effect on cell injury. Moreover, a fluorescent assay confirmed the marked reduction in cell damage following ATP depletion (up to 80% reduction in tunicamycin-pretreated cells). Together, these findings are consistent with the notion that induction of ER molecular chaperones leads to the acquisition of cytoprotection in the face of ATP depletion. However, inhibition of protein translation by cycloheximide was found to only partially attenuate the observed cytoprotective effect, raising the possibility that other, as yet to be identified, nonprotein synthesis-dependent mechanisms may also play a role in the observed cytoprotection.

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