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.

Cytosolic protein quality control machinery: Interactions of Hsp70 with a network of co-chaperones and substrates

2021 ◽  
pp. 153537022199981
Author(s):  
Chamithi Karunanayake ◽  
Richard C Page
Keyword(s):  
Quality Control ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Structural Features ◽  
Cellular Protein ◽  
Mechanisms Of Action ◽  
Control Mechanisms ◽  
Nucleotide Exchange ◽  
Domain Organization ◽  
Nucleotide Exchange Factors

The chaperone heat shock protein 70 (Hsp70) and its network of co-chaperones serve as a central hub of cellular protein quality control mechanisms. Domain organization in Hsp70 dictates ATPase activity, ATP dependent allosteric regulation, client/substrate binding and release, and interactions with co-chaperones. The protein quality control activities of Hsp70 are classified as foldase, holdase, and disaggregase activities. Co-chaperones directly assisting protein refolding included J domain proteins and nucleotide exchange factors. However, co-chaperones can also be grouped and explored based on which domain of Hsp70 they interact. Here we discuss how the network of cytosolic co-chaperones for Hsp70 contributes to the functions of Hsp70 while closely looking at their structural features. Comparison of domain organization and the structures of co-chaperones enables greater understanding of the interactions, mechanisms of action, and roles played in protein quality control.

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 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.

Protein quality control at the ribosome: focus on RAC, NAC and RQC

2016 ◽  
Vol 60 (2) ◽  
pp. 203-212 ◽  
Author(s):  
Martin Gamerdinger
Keyword(s):  
Quality Control ◽  
Protein Production ◽  
Protein Quality ◽  
Nascent Polypeptide ◽  
Life And Death ◽  
Ribosomal Tunnel ◽  
Protein Biogenesis ◽  
Nascent Chain ◽  
Cellular Compartments ◽  
Polypeptide Chains

The biogenesis of new polypeptides by ribosomes and their subsequent correct folding and localization to the appropriate cellular compartments are essential key processes to maintain protein homoeostasis. These complex mechanisms are governed by a repertoire of protein biogenesis factors that directly bind to the ribosome and chaperone nascent polypeptide chains as soon as they emerge from the ribosomal tunnel exit. This nascent chain ‘welcoming committee’ regulates multiple co-translational processes including protein modifications, folding, targeting and degradation. Acting at the front of the protein production line, these ribosome-associated protein biogenesis factors lead the way in the cellular proteostasis network to ensure proteome integrity. In this article, I focus on three different systems in eukaryotes that are critical for the maintenance of protein homoeostasis by controlling the birth, life and death of nascent polypeptide chains.

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.

scholarly journals P209L mutation in Bag3 does not cause cardiomyopathy in mice

2019 ◽  
Vol 316 (2) ◽  
pp. H392-H399 ◽  
Author(s):  
Xi Fang ◽  
Julius Bogomolovas ◽  
Paul Shichao Zhou ◽  
Yongxin Mu ◽  
Xiaolong Ma ◽  
...  
Keyword(s):  
Protein Quality ◽  
Direct Interaction ◽  
Cellular Protein ◽  
Ubiquitinated Proteins ◽  
Small Hsps ◽  
Biochemical Analyses ◽  
Protein Quality Control System ◽  
Species Specific ◽  
Shock Proteins ◽  
Normal Cardiac Function

Bcl-2-associated athanogene 3 (BAG3) is a cochaperone protein and a central player of the cellular protein quality control system. BAG3 is prominently expressed in the heart and plays an essential role in cardiac protein homeostasis by interacting with chaperone heat shock proteins (HSPs) in large, functionally distinct multichaperone complexes. The BAG3 mutation of proline 209 to leucine (P209L), which resides in a critical region that mediates the direct interaction between BAG3 and small HSPs (sHSPs), is associated with cardiomyopathy in humans. However, the mechanism by which the BAG3 P209L missense mutation leads to cardiomyopathy remains unknown. To determine the molecular basis underlying the cardiomyopathy caused by the BAG3 P209L mutation, we generated a knockin (KI) mouse model in which the endogenous Bag3 gene was replaced with mutant Bag3 containing the P215L mutation, which is equivalent to the human P209L mutation. We performed physiological, histological, and biochemical analyses of Bag3 P209L KI mice to determine the functional, morphological, and molecular consequences of the P209L mutation. We found that Bag3 P209L KI mice exhibited normal cardiac function and morphology up to 16 mo of age. Western blot analysis further revealed that levels of sHSPs, stress-inducible HSPs, ubiquitinated proteins, and autophagy were unaffected in P209L mutant mouse hearts. In conclusion, the P209L mutation in Bag3 does not cause cardiomyopathy in mice up to 16 mo of age under baseline conditions. NEW & NOTEWORTHY Bcl-2-associated athanogene 3 (BAG3) P209L mutation is associated with human cardiomyopathy. A recent study reported that transgenic mice overexpressing human BAG3 P209L in cardiomyocytes have cardiac dysfunction. In contrast, our P209L mice that express mutant BAG3 at the same level as that of wild-type mice displayed no overt phenotype. Our results suggest that human cardiomyopathy may result from species-specific requirements for the conserved motif that is disrupted by P209L mutation or from genetic background-dependent effects.

Gold Nanoparticles Induce Cell Stress by Interfering with the Cellular Protein Quality Control System

2020 ◽  
Author(s):  
Guofang Zhang ◽  
Qingle Song ◽  
Yuqian Zhang ◽  
Ruijing Liang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Quality Control ◽  
Er Stress ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Cellular Protein ◽  
Unfolded Proteins ◽  
Unfolded Protein ◽  
Cytokines And Chemokines ◽  
Protein Quality Control System ◽  
Protein Response

Abstract The cellular protein quality control (PQC) system ensures the intracellular misfolded/unfolded proteins to be detected and eliminated. ER-associated degradation (ERAD) and unfolded protein response (UPR) are the key mechanisms of PQC, which maintain protein homeostasis and ensure cell survival. Here, we show that after internalization by human epithelial cells, gold (Au) nanoparticles (NPs) localized in endoplasmic reticulum (ER) and induced an accumulation of misfolded/unfolded proteins. Au NPs activated UPR, but suppressed ERAD shown by a reduced degradation rate of the ERAD marker CD3-δ-YFP, which triggered ER stress through IRE1-XBP1-Chaperones and PERK-eIF2α-ATF4-CHOP pathways. The Au NP-dependent ER stress consequently induced the intracellular accumulation of ROS, and caused cell apoptosis/death, concomitant to production/release of inflammatory cytokines and chemokines. This study for the first time shows that NPs can interfere with the cellular PQC system by impairing ERAD activity, which in turn initiates a cascade of events leading to cell death and inflammation.

scholarly journals Binding of Signal Recognition Particle Gives Ribosome/Nascent Chain Complexes a Competitive Advantage in Endoplasmic Reticulum Membrane Interaction

1998 ◽  
Vol 9 (1) ◽  
pp. 103-115 ◽  
Author(s):  
Andrea Neuhof ◽  
Melissa M. Rolls ◽  
Berit Jungnickel ◽  
Kai-Uwe Kalies ◽  
Tom A. Rapoport
Keyword(s):  
Endoplasmic Reticulum ◽  
Signal Sequence ◽  
Signal Recognition Particle ◽  
Membrane Binding ◽  
Membrane Targeting ◽  
Signal Recognition ◽  
Nascent Polypeptide ◽  
Nascent Chain ◽  
Cytosolic Factors ◽  
Er Membrane

Most secretory and membrane proteins are sorted by signal sequences to the endoplasmic reticulum (ER) membrane early during their synthesis. Targeting of the ribosome-nascent chain complex (RNC) involves the binding of the signal sequence to the signal recognition particle (SRP), followed by an interaction of ribosome-bound SRP with the SRP receptor. However, ribosomes can also independently bind to the ER translocation channel formed by the Sec61p complex. To explain the specificity of membrane targeting, it has therefore been proposed that nascent polypeptide-associated complex functions as a cytosolic inhibitor of signal sequence- and SRP-independent ribosome binding to the ER membrane. We report here that SRP-independent binding of RNCs to the ER membrane can occur in the presence of all cytosolic factors, including nascent polypeptide-associated complex. Nontranslating ribosomes competitively inhibit SRP-independent membrane binding of RNCs but have no effect when SRP is bound to the RNCs. The protective effect of SRP against ribosome competition depends on a functional signal sequence in the nascent chain and is also observed with reconstituted proteoliposomes containing only the Sec61p complex and the SRP receptor. We conclude that cytosolic factors do not prevent the membrane binding of ribosomes. Instead, specific ribosome targeting to the Sec61p complex is provided by the binding of SRP to RNCs, followed by an interaction with the SRP receptor, which gives RNC–SRP complexes a selective advantage in membrane targeting over nontranslating ribosomes.

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