scholarly journals Disrupted structure and aberrant function of CHIP mediates the loss of motor and cognitive function in preclinical models of cerebellar CHIPopathy

2018 ◽  
Author(s):  
Chang-he Shi ◽  
Carrie Rubel ◽  
Sarah E. Soss ◽  
Rebekah Sanchez-Hodge ◽  
Shuo Zhang ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Quality ◽  
Cellular Protein ◽  
Active Member ◽  
Preclinical Models ◽  
Interacting Protein ◽  
Chaperone Function ◽  
On Chip ◽  
Protein Quality Control System ◽  
Ligase Function

AbstractCHIP (carboxyl terminus of heat shock 70-interacting protein) has long been recognized as an active member of the cellular protein quality control system given the ability of CHIP to function as both a co-chaperone and ubiquitin ligase. Mutations in CHIP are the driver of spinocerebellar autosomal recessive 16 (SCAR16), or cerebellar CHIPopathy, as we initially discovered this disease was caused by a loss of CHIP ubiquitin ligase function. The initial mutation describing SCAR16 was a missense mutation in the ubiquitin ligase domain of CHIP (p.T246M). Using multiple biophysical and cellular approaches, we demonstrate that T246M mutation results in structural disorganization and misfolding of the CHIP U-box domain, promoting oligomerization, and increased proteasome-dependent turnover. CHIP-T246M has no ligase activity, but maintains interactions with chaperones and alters the co-chaperone function of CHIP. To establish preclinical models of SCAR16, we engineered T246M at the endogenous locus in both mice and rats. Animals homozygous for T246M had both cognitive and motor cerebellar dysfunction distinct from those observed in the CHIP null animal model, as well as deficits in learning and memory, reflective of the cognitive deficits reported in SCAR16 patients. We conclude that the T246M mutation is not equivalent to the total loss of CHIP, supporting the concept that disease-causing CHIP mutations have different biophysical and functional repercussions on CHIP function that may directly correlate to the spectrum of clinical phenotypes observed in SCAR16 patients. Our findings both further expand our basic understanding of CHIP biology and provide meaningful mechanistic insight underlying the molecular drivers of SCAR16 disease pathology, which may be used to inform the development of novel therapeutics for this devastating disease.

scholarly journals The Crystal Structure of Archaeal Nascent Polypeptide-associated Complex (NAC) Reveals a Unique Fold and the Presence of a Ubiquitin-associated Domain

2005 ◽  
Vol 280 (16) ◽  
pp. 15849-15854 ◽  
Author(s):  
Thomas Spreter ◽  
Markus Pech ◽  
Birgitta Beatrix
Keyword(s):  
Crystal Structure ◽  
Protein Quality ◽  
Structural Features ◽  
Cellular Protein ◽  
Nascent Polypeptide ◽  
Nascent Chain ◽  
Ubiquitination Pathway ◽  
Protein Quality Control System ◽  
Cytosolic Factor ◽  
Cytosolic Factors

Nascent polypeptide-associated complex (NAC) was identified in eukaryotes as the first cytosolic factor that contacts the nascent polypeptide chain emerging from the ribosome. NAC is highly conserved from yeast to humans. Mutations in NAC cause severe embryonically lethal phenotypes in mice,Drosophila,andCaenorhabditis elegans.NAC was suggested to protect the nascent chain from inappropriate early interactions with cytosolic factors. Eukaryotic NAC is a heterodimer with two subunits sharing substantial homology with each other. All sequenced archaebacterial genomes exhibit only one gene homologous to the NAC subunits. Here we present the first archaebacterial NAC homolog. It forms a homodimer, and as eukaryotic NAC it is associated with ribosomes and contacts the emerging nascent chain on the ribosome. We present the first crystal structure of a NAC protein revealing two structural features: (i) a novel unique protein fold that mediates dimerization of the complex, and (ii) a ubiquitin-associated domain that suggests a yet unidentified role for NAC in the cellular protein quality control system via the ubiquitination pathway. Based on the presented structure we propose a model for the eukaryotic heterodimeric NAC domain.

scholarly journals Truncation-Driven Lateral Association of α-Synuclein Hinders Amyloid Clearance by the Hsp70-based Disaggregase

2021 ◽  
Vol 22 (23) ◽  
pp. 12983
Author(s):  
Aitor Franco ◽  
Jorge Cuéllar ◽  
José Ángel Fernández-Higuero ◽  
Igor de la Arada ◽  
Natalia Orozco ◽  
...  
Keyword(s):  
Neurodegenerative Disorders ◽  
Protein Quality ◽  
Mechanical Action ◽  
Cellular Protein ◽  
Type B ◽  
Post Translational Modifications ◽  
Lateral Association ◽  
N Terminus ◽  
Protein Quality Control System

The aggregation of α-synuclein is the hallmark of a collective of neurodegenerative disorders known as synucleinopathies. The tendency to aggregate of this protein, the toxicity of its aggregation intermediates and the ability of the cellular protein quality control system to clear these intermediates seems to be regulated, among other factors, by post-translational modifications (PTMs). Among these modifications, we consider herein proteolysis at both the N- and C-terminal regions of α-synuclein as a factor that could modulate disassembly of toxic amyloids by the human disaggregase, a combination of the chaperones Hsc70, DnaJB1 and Apg2. We find that, in contrast to aggregates of the protein lacking the N-terminus, which can be solubilized as efficiently as those of the WT protein, the deletion of the C-terminal domain, either in a recombinant context or as a consequence of calpain treatment, impaired Hsc70-mediated amyloid disassembly. Progressive removal of the negative charges at the C-terminal region induces lateral association of fibrils and type B* oligomers, precluding chaperone action. We propose that truncation-driven aggregate clumping impairs the mechanical action of chaperones, which includes fast protofilament unzipping coupled to depolymerization. Inhibition of the chaperone-mediated clearance of C-truncated species could explain their exacerbated toxicity and higher propensity to deposit found in vivo.

scholarly journals E3 ubiquitin ligase CHIP facilitates Toll-like receptor signaling by recruiting and polyubiquitinating Src and atypical PKCζ

2011 ◽  
Vol 208 (10) ◽  
pp. 2099-2112 ◽  
Author(s):  
Mingjin Yang ◽  
Chen Wang ◽  
Xuhui Zhu ◽  
Songqing Tang ◽  
Liyun Shi ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Quality ◽  
E3 Ubiquitin Ligase ◽  
Resistant Mutant ◽  
Toll Like Receptor ◽  
Tlr Signaling ◽  
Interacting Protein ◽  
Signaling Complex ◽  
Antigen Presenting ◽  
Mutant Forms

The carboxyl terminus of constitutive heat shock cognate 70 (HSC70)–interacting protein (CHIP, also known as Stub1) is a U box–containing E3 ubiquitin ligase that is important for protein quality control. The role of CHIP in innate immunity is not known. Here, we report that CHIP knockdown inhibits Toll-like receptor (TLR) 4– and TLR9-driven signaling, but not TLR3-driven signaling; proinflammatory cytokine and type 1 interferon (IFN) production; and maturation of antigen-presenting cells, including macrophages and dendritic cells. We demonstrate that CHIP can recruit the tyrosine kinase Src and atypical protein kinase C ζ (PKCζ) to the TLR complex, thereby leading to activation of IL-1 receptor–associated kinase 1, TANK-binding kinase 1, and IFN regulatory factors 3 and 7. CHIP acts as an E3 ligase for Src and PKCζ during TLR signaling. CHIP-mediated enhancement of TLR signaling is inhibited by IFNAR deficiency or expression of ubiquitination resistant mutant forms of Src or PKCζ. These findings suggest that CHIP facilitates the formation of a TLR signaling complex by recruiting, ubiquitinating, and activating Src and PKCζ.

scholarly journals BAG-2 Acts as an Inhibitor of the Chaperone-associated Ubiquitin Ligase CHIP

2005 ◽  
Vol 16 (12) ◽  
pp. 5891-5900 ◽  
Author(s):  
Verena Arndt ◽  
Christina Daniel ◽  
Wolfgang Nastainczyk ◽  
Simon Alberti ◽  
Jörg Höhfeld
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Quality ◽  
Protein Complexes ◽  
Peptide Mass Fingerprinting ◽  
Ubiquitin Proteasome System ◽  
Degradation Pathway ◽  
Cellular Protein ◽  
Ubiquitin Chain ◽  
Peptide Mass ◽  
Main Component

Cellular protein quality control involves a close interplay between molecular chaperones and the ubiquitin/proteasome system. We recently identified a degradation pathway, on which the chaperone Hsc70 delivers chaperone clients, such as misfolded forms of the cystic fibrosis transmembrane conductance regulator (CFTR), to the proteasome. The cochaperone CHIP is of central importance on this pathway, because it acts as a chaperone-associated ubiquitin ligase. CHIP mediates the attachment of a ubiquitin chain to a chaperone-presented client protein and thereby stimulates its proteasomal degradation. To gain further insight into the function of CHIP we isolated CHIP-containing protein complexes from human HeLa cells and analyzed their composition by peptide mass fingerprinting. We identified the Hsc70 cochaperone BAG-2 as a main component of CHIP complexes. BAG-2 inhibits the ubiquitin ligase activity of CHIP by abrogating the CHIP/E2 cooperation and stimulates the chaperone-assisted maturation of CFTR. The activity of BAG-2 resembles that of the previously characterized Hsc70 cochaperone and CHIP inhibitor HspBP1. The presented data therefore establish multiple mechanisms to control the destructive activity of the CHIP ubiquitin ligase in human cells.

scholarly journals Conserved and Unique Roles of Chaperone-Dependent E3 Ubiquitin Ligase CHIP in Plants

2021 ◽  
Vol 12 ◽  
Author(s):  
Yan Zhang ◽  
Gengshou Xia ◽  
Qianggen Zhu
Keyword(s):  
Ubiquitin Ligase ◽  
Stress Responses ◽  
Protein Misfolding ◽  
Protein Quality ◽  
Plant Signaling ◽  
Interacting Protein ◽  
Native Proteins ◽  
C Terminus ◽  
Crucial Component ◽  
Carboxy Terminal

Protein quality control (PQC) is essential for maintaining cellular homeostasis by reducing protein misfolding and aggregation. Major PQC mechanisms include protein refolding assisted by molecular chaperones and the degradation of misfolded and aggregated proteins using the proteasome and autophagy. A C-terminus of heat shock protein (Hsp) 70-interacting protein [carboxy-terminal Hsp70-interacting protein (CHIP)] is a chaperone-dependent and U-box-containing E3 ligase. CHIP is a key molecule in PQC by recognizing misfolded proteins through its interacting chaperones and targeting their degradation. CHIP also ubiquitinates native proteins and plays a regulatory role in other cellular processes, including signaling, development, DNA repair, immunity, and aging in metazoans. As a highly conserved ubiquitin ligase, plant CHIP plays an important role in response to a broad spectrum of biotic and abiotic stresses. CHIP protects chloroplasts by coordinating chloroplast PQC both outside and inside the important photosynthetic organelle of plant cells. CHIP also modulates the activity of protein phosphatase 2A (PP2A), a crucial component in a network of plant signaling, including abscisic acid (ABA) signaling. In this review, we discuss the structure, cofactors, activities, and biological function of CHIP with an emphasis on both its conserved and unique roles in PQC, stress responses, and signaling in plants.

scholarly journals p62-containing, proteolytically active nuclear condensates, increase the efficiency of the ubiquitin–proteasome system

2021 ◽  
Vol 118 (33) ◽  
pp. e2107321118
Author(s):  
Afu Fu ◽  
Victoria Cohen-Kaplan ◽  
Noa Avni ◽  
Ido Livneh ◽  
Aaron Ciechanover
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Quality ◽  
Ubiquitin Proteasome System ◽  
Cellular Protein ◽  
26S Proteasome ◽  
Ubiquitin Chain ◽  
Recognition Element ◽  
Oxidative Stresses ◽  
Ubiquitin Ligase E3 ◽  
Ubiquitin Proteasome

Degradation of a protein by the ubiquitin–proteasome system (UPS) is a multistep process catalyzed by sequential reactions. Initially, ubiquitin is conjugated to the substrate in a process mediated by concerted activity of three enzymes; the last of them—a ubiquitin ligase (E3)—belongs to a family of several hundred members, each recognizing a few specific substrates. This is followed by repeated addition of ubiquitin moieties to the previously conjugated one to generate a ubiquitin chain that serves as a recognition element for the proteasome, which then degrades the substrate. Ubiquitin is recycled via the activity of deubiquitinating enzymes (DUBs). It stands to reason that efficiency of such a complex process would depend on colocalization of the different components in an assembly that allows the reactions to be carried out sequentially and processively. Here we describe nuclear condensates that are dynamic in their composition. They contain p62 as an essential component. These assemblies are generated by liquid–liquid phase separation (LLPS) and also contain ubiquitinated targets, 26S proteasome, the three conjugating enzymes, and DUBs. Under basal conditions, they serve as efficient centers for proteolysis of nuclear proteins (e.g., c-Myc) and unassembled subunits of the proteasome, suggesting they are involved in cellular protein quality control. Supporting this notion is the finding that such foci are also involved in degradation of misfolded proteins induced by heat and oxidative stresses, following recruitment of heat shock proteins and their associated ubiquitin ligase CHIP.

scholarly journals CRL2 aids elimination of truncated selenoproteins produced by failed UGA/Sec decoding

Science ◽  
2015 ◽  
Vol 349 (6243) ◽  
pp. 91-95 ◽  
Author(s):  
Hsiu-Chuan Lin ◽  
Szu-Chi Ho ◽  
Yi-Yun Chen ◽  
Kay-Hooi Khoo ◽  
Pang-Hung Hsu ◽  
...  
Keyword(s):  
Quality Control ◽  
Control System ◽  
Protein Degradation ◽  
Genetic Code ◽  
Ubiquitin Ligase ◽  
Protein Quality ◽  
Translation Termination ◽  
Protein Quality Control ◽  
Selenium Intake ◽  
Protein Quality Control System

Selenocysteine (Sec) is translated from the codon UGA, typically a termination signal. Codon duality extends the genetic code; however, the coexistence of two competing UGA-decoding mechanisms immediately compromises proteome fidelity. Selenium availability tunes the reassignment of UGA to Sec. We report a CRL2 ubiquitin ligase–mediated protein quality-control system that specifically eliminates truncated proteins that result from reassignment failures. Exposing the peptide immediately N-terminal to Sec, a CRL2 recognition degron, promotes protein degradation. Sec incorporation destroys the degron, protecting read-through proteins from detection by CRL2. Our findings reveal a coupling between directed translation termination and proteolysis-assisted protein quality control, as well as a cellular strategy to cope with fluctuations in organismal selenium intake.

The HSP70 chaperone as sensor of the NEDD8 cycle upon DNA damage

2021 ◽  
Author(s):  
Aymeric P. Bailly ◽  
Dimitris P. Xirodimas
Keyword(s):  
Dna Damage ◽  
Protein Quality ◽  
Atp Hydrolysis ◽  
Regulatory Modules ◽  
Chaperone Function ◽  
Regulatory Module ◽  
Essential Components ◽  
Evolutionarily Conserved ◽  
Hsp70 Chaperone ◽  
Protein Quality Control System

Molecular chaperones are essential components of the protein quality control system and maintenance of homeostasis. Heat Shock Protein 70 (HSP70), a highly evolutionarily conserved family of chaperones is a key regulator of protein folding, oligomerisation and prevents the aggregation of misfolded proteins. HSP70 chaperone function depends on the so-called ‘HSP70-cycle', where HSP70 interacts with and is released from substrates via ATP hydrolysis and the assistance of HSP70 co-factors/co-chaperones, which also provide substrate specificity. The identification of regulatory modules for HSP70 allows the elucidation of HSP70 specificity and target selectivity. Here, we discuss how the HSP70 cycle is functionally linked with the cycle of the Ubiquitin-like molecule NEDD8. Using as an example the DNA damage response, we present a model where HSP70 acts as a sensor of the NEDD8 cycle. The NEDD8 cycle acts as a regulatory module of HSP70 activity, where conversion of poly-NEDD8 chains into mono-NEDD8 upon DNA damage activates HSP70, facilitating the formation of the apoptosome and apoptosis execution.

Shape matters: the complex relationship between aggregation and toxicity in protein-misfolding diseases

2016 ◽  
Vol 60 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Heidrun Maja Ries ◽  
Carmen Nussbaum-Krammer
Keyword(s):  
Protein Misfolding ◽  
Protein Quality ◽  
Cellular Protein ◽  
Exact Nature ◽  
High Tendency ◽  
Protein Deposits ◽  
Cellular Environment ◽  
Individual Interaction ◽  
Protein Quality Control System ◽  
Misfolding Diseases

A particular subgroup of protein-misfolding diseases, comprising Alzheimer's and Parkinson's disease, involves amyloidogenic proteins that can form alternative pathogenic conformations with a high tendency to self-assemble into oligomeric and fibrillar species. Although misfolded proteins have been clearly linked to disease, the exact nature of the toxic species remains highly controversial. Increasing evidence suggests that there is little correlation between the occurrence of macroscopic protein deposits and toxic phenotypes in affected cells and tissues. In this article, we recap amyloid aggregation pathways, describe prion-like propagation, elaborate on detrimental interactions of protein aggregates with the cellular protein quality control system and discuss why some aggregates are toxic, whereas others seem to be beneficial. On the basis of recent studies on prion strains, we reason that the specific aggregate conformation and the resulting individual interaction with the cellular environment might be the major determinant of toxicity.

scholarly journals DEG10 contributes to mitochondrial proteostasis, root growth, and seed yield in Arabidopsis

2019 ◽  
Vol 70 (19) ◽  
pp. 5423-5436 ◽  
Author(s):  
Catharina V Huber ◽  
Barbara D Jakobs ◽  
Laxmi S Mishra ◽  
Stefan Niedermaier ◽  
Marc Stift ◽  
...  
Keyword(s):  
Vascular Tissue ◽  
Protein Quality ◽  
Proteome Analysis ◽  
Mitochondrial Respiratory Chain ◽  
Cellular Protein ◽  
Cell Fractionation ◽  
Loss Of Function ◽  
Mitochondrial Proteome ◽  
Atp Supply ◽  
Protein Quality Control System

AbstractMaintaining mitochondrial proteome integrity is especially important under stress conditions to ensure a continued ATP supply for protection and adaptation responses in plants. Deg/HtrA proteases are important factors in the cellular protein quality control system, but little is known about their function in mitochondria. Here we analyzed the expression pattern and physiological function of Arabidopsis thaliana DEG10, which has homologs in all photosynthetic eukaryotes. Both expression of DEG10:GFP fusion proteins and immunoblotting after cell fractionation showed an unambiguous subcellular localization exclusively in mitochondria. DEG10 promoter:GUS fusion constructs showed that DEG10 is expressed in trichomes but also in the vascular tissue of roots and aboveground organs. DEG10 loss-of-function mutants were impaired in root elongation, especially at elevated temperature. Quantitative proteome analysis revealed concomitant changes in the abundance of mitochondrial respiratory chain components and assembly factors, which partially appeared to depend on altered mitochondrial retrograde signaling. Under field conditions, lack of DEG10 caused a decrease in seed production. Taken together, our findings demonstrate that DEG10 affects mitochondrial proteostasis, is required for optimal root development and seed set under challenging environmental conditions, and thus contributes to stress tolerance of plants.

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