Differential HspBP1 expression accounts for the greater vulnerability of neurons than astrocytes to misfolded proteins

Although it is well known that astrocytes are less vulnerable than neurons in neurodegenerative diseases, the mechanism behind this differential vulnerability is unclear. Here we report that neurons and astrocytes show markedly different activities in C terminus of Hsp70-interacting protein (CHIP), a cochaperone of Hsp70. In astrocytes, CHIP is more actively monoubiquitinated and binds to mutant huntingtin (mHtt), the Huntington’s disease protein, more avidly, facilitating its K48-linked polyubiquitination and degradation. Astrocytes also show the higher level and heat-shock induction of Hsp70 and faster CHIP-mediated degradation of various misfolded proteins than neurons. In contrast to astrocytes, neurons express abundant HspBP1, a CHIP inhibitory protein, resulting in the low activity of CHIP. Silencing HspBP1 expression via CRISPR-Cas9 in neurons ameliorated mHtt aggregation and neuropathology in HD knockin mouse brains. Our findings indicate a critical role of HspBP1 in differential CHIP/Hsp70 activities in neuronal and glial cells and the greater neuronal vulnerability to misfolded proteins in neurodegenerative diseases.

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Molecular basis of the dual role of the Mlh1-Mlh3 endonuclease in MMR and in meiotic crossover formation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2022704118 ◽

2021 ◽

Vol 118 (23) ◽

pp. e2022704118

Author(s):

Jingqi Dai ◽

Aurore Sanchez ◽

Céline Adam ◽

Lepakshi Ranjha ◽

Giordano Reginato ◽

...

Keyword(s):

Meiotic Recombination ◽

Molecular Basis ◽

Crystal Packing ◽

Critical Role ◽

Holliday Junctions ◽

Dual Roles ◽

Terminal Domain ◽

C Terminus ◽

Meiotic Crossover

In budding yeast, the MutL homolog heterodimer Mlh1-Mlh3 (MutLγ) plays a central role in the formation of meiotic crossovers. It is also involved in the repair of a subset of mismatches besides the main mismatch repair (MMR) endonuclease Mlh1-Pms1 (MutLα). The heterodimer interface and endonuclease sites of MutLγ and MutLα are located in their C-terminal domain (CTD). The molecular basis of MutLγ’s dual roles in MMR and meiosis is not known. To better understand the specificity of MutLγ, we characterized the crystal structure of Saccharomyces cerevisiae MutLγ(CTD). Although MutLγ(CTD) presents overall similarities with MutLα(CTD), it harbors some rearrangement of the surface surrounding the active site, which indicates altered substrate preference. The last amino acids of Mlh1 participate in the Mlh3 endonuclease site as previously reported for Pms1. We characterized mlh1 alleles and showed a critical role of this Mlh1 extreme C terminus both in MMR and in meiotic recombination. We showed that the MutLγ(CTD) preferentially binds Holliday junctions, contrary to MutLα(CTD). We characterized Mlh3 positions on the N-terminal domain (NTD) and CTD that could contribute to the positioning of the NTD close to the CTD in the context of the full-length MutLγ. Finally, crystal packing revealed an assembly of MutLγ(CTD) molecules in filament structures. Mutation at the corresponding interfaces reduced crossover formation, suggesting that these superstructures may contribute to the oligomer formation proposed for MutLγ. This study defines clear divergent features between the MutL homologs and identifies, at the molecular level, their specialization toward MMR or meiotic recombination functions.

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CTCF cooperates with CtIP to drive homologous recombination repair of double-strand breaks

Nucleic Acids Research ◽

10.1093/nar/gkz639 ◽

2019 ◽

Vol 47 (17) ◽

pp. 9160-9179 ◽

Cited By ~ 6

Author(s):

Soon Young Hwang ◽

Mi Ae Kang ◽

Chul Joon Baik ◽

Yejin Lee ◽

Ngo Thanh Hang ◽

...

Keyword(s):

Homologous Recombination ◽

Critical Role ◽

Control Point ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

C Terminus ◽

Dna End Resection ◽

End Resection

Abstract The pleiotropic CCCTC-binding factor (CTCF) plays a role in homologous recombination (HR) repair of DNA double-strand breaks (DSBs). However, the precise mechanistic role of CTCF in HR remains largely unclear. Here, we show that CTCF engages in DNA end resection, which is the initial, crucial step in HR, through its interactions with MRE11 and CtIP. Depletion of CTCF profoundly impairs HR and attenuates CtIP recruitment at DSBs. CTCF physically interacts with MRE11 and CtIP and promotes CtIP recruitment to sites of DNA damage. Subsequently, CTCF facilitates DNA end resection to allow HR, in conjunction with MRE11–CtIP. Notably, the zinc finger domain of CTCF binds to both MRE11 and CtIP and enables proficient CtIP recruitment, DNA end resection and HR. The N-terminus of CTCF is able to bind to only MRE11 and its C-terminus is incapable of binding to MRE11 and CtIP, thereby resulting in compromised CtIP recruitment, DSB resection and HR. Overall, this suggests an important function of CTCF in DNA end resection through the recruitment of CtIP at DSBs. Collectively, our findings identify a critical role of CTCF at the first control point in selecting the HR repair pathway.

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Proteinopathies and OXPHOS dysfunction in neurodegenerative diseases

The Journal of Cell Biology ◽

10.1083/jcb.201709172 ◽

2017 ◽

Vol 216 (12) ◽

pp. 3917-3929 ◽

Cited By ~ 34

Author(s):

Hibiki Kawamata ◽

Giovanni Manfredi

Keyword(s):

Nervous System ◽

Oxidative Phosphorylation ◽

Neurodegenerative Diseases ◽

Gene Mutations ◽

Misfolded Proteins ◽

Protein Homeostasis ◽

Abnormal Protein ◽

Oxidative Phosphorylation System ◽

Intermediate Metabolism

Mitochondria participate in essential processes in the nervous system such as energy and intermediate metabolism, calcium homeostasis, and apoptosis. Major neurodegenerative diseases are characterized pathologically by accumulation of misfolded proteins as a result of gene mutations or abnormal protein homeostasis. Misfolded proteins associate with mitochondria, forming oligomeric and fibrillary aggregates. As mitochondrial dysfunction, particularly of the oxidative phosphorylation system (OXPHOS), occurs in neurodegeneration, it is postulated that such defects are caused by the accumulation of misfolded proteins. However, this hypothesis and the pathological role of proteinopathies in mitochondria remain elusive. In this study, we critically review the proposed mechanisms whereby exemplary misfolded proteins associate with mitochondria and their consequences on OXPHOS.

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Critical role of X-box binding protein 1 in NADPH oxidase 4-triggered cardiac hypertrophy is mediated by receptor interacting protein kinase 1

Cell Cycle ◽

10.1080/15384101.2016.1260210 ◽

2017 ◽

Vol 16 (4) ◽

pp. 348-359 ◽

Cited By ~ 7

Author(s):

Li Chen ◽

Mingyue Zhao ◽

Junli Li ◽

Yu Wang ◽

Qinxue Bao ◽

...

Keyword(s):

Protein Kinase ◽

Nadph Oxidase ◽

Cardiac Hypertrophy ◽

Binding Protein ◽

Critical Role ◽

Interacting Protein ◽

Nadph Oxidase 4

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A Critical Role of c-Cbl-Interacting Protein of 85 kDa in the Development and Progression of Head and Neck Squamous Cell Carcinomas through the Ras-ERK Pathway

Neoplasia ◽

10.1593/neo.10396 ◽

2010 ◽

Vol 12 (10) ◽

pp. 789-IN4 ◽

Cited By ~ 22

Author(s):

Takahiro Wakasaki ◽

Muneyuki Masuda ◽

Hiroaki Niiro ◽

Siamak Jabbarzadeh-Tabrizi ◽

Kumiko Noda ◽

...

Keyword(s):

Head And Neck ◽

Squamous Cell ◽

Critical Role ◽

Squamous Cell Carcinomas ◽

Erk Pathway ◽

Interacting Protein

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Specificity of Baculovirus P6.9 Basic DNA-Binding Proteins and Critical Role of the C Terminus in Virion Formation

Journal of Virology ◽

10.1128/jvi.00072-10 ◽

2010 ◽

Vol 84 (17) ◽

pp. 8821-8828 ◽

Cited By ~ 30

Author(s):

Manli Wang ◽

Era Tuladhar ◽

Shu Shen ◽

Hualin Wang ◽

Monique M. van Oers ◽

...

Keyword(s):

Virus Assembly ◽

Critical Role ◽

Nucleocapsid Proteins ◽

Double Stranded Dna ◽

C Terminus ◽

Sequence Elements ◽

Eukaryotic Organisms ◽

Dsdna Viruses ◽

Virion Formation

ABSTRACT The majority of double-stranded DNA (dsDNA) viruses infecting eukaryotic organisms use host- or virus-expressed histones or protamine-like proteins to condense their genomes. In contrast, members of the Baculoviridae family use a protamine-like protein named P6.9. The dephosphorylated form of P6.9 binds to DNA in a non-sequence-specific manner. By using a p6.9-null mutant of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), we demonstrate that P6.9 is not required for viral DNA replication but is essential for the production of infectious virus. Virion production was rescued by P6.9 homologs from a number of Alpha baculovirus species and one Gammabaculovirus species but not from the genus Betabaculovirus, comprising the granuloviruses, or by the P6.9 homolog VP15 from the unrelated white spot syndrome virus of shrimp. Mutational analyses demonstrated that AcMNPV P6.9 with a conserved 11-residue deletion of the C terminus was not capable of rescuing p6.9-null AcMNPV, while a chimeric Betabaculovirus P6.9 containing the P6.9 C-terminal region of an Alphabaculovirus strain was able to do so. This implies that the C terminus of baculovirus P6.9 contains sequence elements essential for virion formation. Such elements may possibly interact with species- or genus-specific domains of other nucleocapsid proteins during virus assembly.

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Chaperone-mediated hierarchical control in targeting misfolded proteins to aggresomes

Molecular Biology of the Cell ◽

10.1091/mbc.e11-05-0388 ◽

2011 ◽

Vol 22 (18) ◽

pp. 3277-3288 ◽

Cited By ~ 55

Author(s):

Xingqian Zhang ◽

Shu-Bing Qian

Keyword(s):

Protein Folding ◽

Protein Misfolding ◽

Mammalian Cells ◽

Molecular Mechanisms ◽

Hierarchical Control ◽

Dominant Negative ◽

Misfolded Proteins ◽

Interacting Protein ◽

Aggresome Formation

Protein misfolding is a common event in living cells. Molecular chaperones not only assist protein folding; they also facilitate the degradation of misfolded polypeptides. When the intracellular degradative capacity is exceeded, juxtanuclear aggresomes are formed to sequester misfolded proteins. Despite the well-established role of chaperones in both protein folding and degradation, how chaperones regulate the aggregation process remains controversial. Here we investigate the molecular mechanisms underlying aggresome formation in mammalian cells. Analysis of the chaperone requirements for the fate of misfolded proteins reveals an unexpected role of heat shock protein 70 (Hsp70) in promoting aggresome formation. This proaggregation function of Hsp70 relies on the interaction with the cochaperone ubiquitin ligase carboxyl terminal of Hsp70/Hsp90 interacting protein (CHIP). Disrupting Hsp70–CHIP interaction prevents the aggresome formation, whereas a dominant-negative CHIP mutant sensitizes the aggregation of misfolded protein. This accelerated aggresome formation also relies on the stress-induced cochaperone Bcl2-associated athanogene 3. Our results indicate that a hierarchy of cochaperone interaction controls different aspects of the intracellular protein triage decision, extending the function of Hsp70 from folding and degradation to aggregation.

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Structure of APP-C991-99 and Implications for Role of Extra-Membrane Domains in Function and Oligomerization

10.1101/257469 ◽

2018 ◽

Author(s):

George A. Pantelopulos ◽

John E. Straub ◽

D. Thirumalai ◽

Yuji Sugita

Keyword(s):

Transmembrane Domain ◽

Chemical Shifts ◽

Membrane Surface ◽

Critical Role ◽

Amyloid Formation ◽

Cytoplasmic Proteins ◽

C Terminus ◽

N Terminus ◽

Thin Membranes

AbstractThe 99 amino acid C-terminal fragment of Amyloid Precursor Protein APP-C99 (C99) is cleaved by γ-secretase to form Aβ peptide, which plays a critical role in the etiology of Alzheimer’s Disease (AD). The structure of C99 consists of a single transmembrane domain flanked by intra and intercellular domains. While the structure of the transmembrane domain has been well characterized, little is known about the structure of the flanking domains and their role in C99 processing by γ-secretase. To gain insight into the structure of full-length C99, REMD simulations were performed for monomeric C99 in model membranes of varying thickness. We find equilibrium ensembles of C99 from simulation agree with experimentally-inferred residue insertion depths and protein backbone chemical shifts. In thin membranes, the transmembrane domain structure is correlated with extra-membrane structural states. Mean and variance of the transmembrane and G37G38 hinge angles are found to increase with thinning membrane. The N-terminus of C99 forms β-strands that may seed aggregation of Aβ on the membrane surface, promoting amyloid formation. The N-terminus, which forms α-helices that interact with the nicastrin domain of γ-secretase. The C-terminus of C99 becomes more α-helical as the membrane thickens, forming structures that may be suitable for binding by cytoplasmic proteins, while C-terminal residues essential to cytotoxic function become α-helical as the membrane thins. The heterogeneous but discrete extra-membrane domain states analyzed here open the path to new investigations of the role of C99 structure and membrane in amyloidogenesis.

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