Protein folding

  • Article
    | Open Access

    Protein binding by the Hsp70/J-domain protein (JDP) chaperones prevents aggregation of the client protein. Here, the authors show that DnaJC7 binds preferentially to natively folded wild-type tau, via a β-turn element in tau that contains the known amyloid motif, while aggregation-prone tau mutants are recognized with reduced affinity.

    • Zhiqiang Hou
    • , Pawel M. Wydorski
    •  & Lukasz A. Joachimiak
  • Article
    | Open Access

    Bacterial surface adhesion proteins are characterized by unusual mechanical properties. Here, the authors use atomic force microscopy-based technique to study a surface-anchoring protein Cpe0147 from Clostridium perfringens and show that an ester bond can withstand considerable mechanical forces and prevent complete protein unfolding.

    • Hai Lei
    • , Quan Ma
    •  & Yi Cao
  • Article
    | Open Access

    Variants of the extracellular chaperone Clusterin are associated with Alzheimer’s disease (AD) and Clusterin levels are elevated in AD patient brains. Here, the authors show that Clusterin binds to oligomeric Tau, which enhances the seeding capacity of Tau aggregates upon cellular uptake. They also demonstrate that Tau/Clusterin complexes enter cells via the endosomal pathway, resulting in damage to endolysosomes and entry into the cytosol, where they induce the aggregation of endogenous, soluble Tau.

    • Patricia Yuste-Checa
    • , Victoria A. Trinkaus
    •  & F. Ulrich Hartl
  • Article
    | Open Access

    RPAP3 is a subunit of the R2TP complex, a co-chaperone of HSP90, with substrate proteins involved in transcription, ribosome biogenesis, DNA repair and cell growth. Here the authors report that deletion of Rpap3 abrogates cell proliferation and homeostasis in mouse intestine, partly through destabilization of PI3K-like kinases, while elevated RPAP3 levels in colorectal tumors are associated with poor prognosis.

    • Chloé Maurizy
    • , Claire Abeza
    •  & Bérengère Pradet-Balade
  • Article
    | Open Access

    Aβ oligomers (AβO) are thought to represent the main toxic species in Alzheimer’s disease but very high Aβ concentrations are required to study them in vitro and it remains unknown what role these off-pathway oligomers play in vivo. Here, the authors use a dimeric variant of Aβ termed dimAβ, where two Aβ40 units are linked, which facilitates to study AβO formation kinetics and they observe that Aβ off-pathway oligomer formation is strongly accelerated at endo-lysosomal pH, while amyloid fibril formation is delayed. Furthermore, the authors demonstrate that dimAβ is a disease-relevant model construct for pathogenic AβO formation by showing that dimAβ AβOs target dendritic spines and induce AD-like somatodendritic Tau missorting.

    • Marie P. Schützmann
    • , Filip Hasecke
    •  & Wolfgang Hoyer
  • Article
    | Open Access

    Huntingtin exon-1 (HTTex1) consists of a N-terminal N17 domain, the disease causing polyQ domain and a C-terminal proline-rich domain (PRD). Here, the authors combine electron paramagnetic resonance (EPR), solid-state NMR with other biophysical method to characterise the structural differences of various HTTex1 fibril types with different toxicity and find that the dynamics and entanglement of the PRD domain differs among them and that the HTTex1 fibrils can be interconverted.

    • J. Mario Isas
    • , Nitin K. Pandey
    •  & Ansgar B. Siemer
  • Article
    | Open Access

    The folding of outer membrane proteins (OMPs) is catalyzed by the βbarrel assembly machinery (BAM). Here, structural and functional analyses of BAM stabilized in distinct conformations elucidate the roles of lateral gate opening and interactions of BAM with the lipid bilayer in OMP assembly.

    • Paul White
    • , Samuel F. Haysom
    •  & Sheena E. Radford
  • Article
    | Open Access

    Amyloid aggregation of mutant p53 contributes to its loss of tumor suppressor function and oncogenic gain-of-function. Here, the authors use a protein mimetic to abrogate mutant p53 aggregation and rescue p53 function, which inhibits cancer cell proliferation in vitro and halts tumor growth in vivo.

    • L. Palanikumar
    • , Laura Karpauskaite
    •  & Mazin Magzoub
  • Article
    | Open Access

    α-Synuclein (αS) aggregation is a driver of several neurodegenerative disorders. Here, the authors identify a class of peptides that bind toxic αS oligomers and amyloid fibrils but not monomeric functional protein, and prevent further αS aggregation and associated cell damage.

    • Jaime Santos
    • , Pablo Gracia
    •  & Salvador Ventura
  • Article
    | Open Access

    Structural insights into the small heat shock proteins (sHsps) complexes with their substrates are sparse. Here, cryo-EM structure of a plastid sHsp, Hsp21, in complex with a bona fide substrate 1-deoxy-D-xylulose 5-phosphate synthase (DXPS), suggests the anti-aggregation mechanism employed by sHsps.

    • Chuanyang Yu
    • , Stephen King Pong Leung
    •  & Wilson Chun Yu Lau
  • Article
    | Open Access

    The ER chaperone BiP is critical for the unfolded protein response and tightly regulated through reversible AMPylation by FICD, but the structural basis is unknown. Here the authors use thiol-reactive nucleotide derivatives to stabilize the transient FICD:BiP complex and determine its crystal structure.

    • Joel Fauser
    • , Burak Gulen
    •  & Aymelt Itzen
  • Article
    | Open Access

    Wobble uridine (U34) tRNA modifications are important for the decoding of AA-ending codons. Here the authors show that while the U34-codon content of mRNAs are predictive of changes in ribosome translation elongation, the resulting outcome in protein expression also relies on specific hydrophilic motifs-dependent protein aggregation and clearance.

    • Francesca Rapino
    • , Zhaoli Zhou
    •  & Pierre Close
  • Article
    | Open Access

    Glycoprotein US9 of human cytomegalovirus downregulates the activating immune ligand MICA*008 to avoid NK cell activation. Here, Seidel et al. show that the signal peptide of US9 is cleaved unusually slowly, causing MICA*008 to be retained in the endoplasmic reticulum (ER) and degraded via the ER quality control system.

    • Einat Seidel
    • , Liat Dassa
    •  & Ofer Mandelboim
  • Article
    | Open Access

    The self-assembly of α-synuclein (αS) is a pathological feature of Parkinson’s disease. The αS species responsible for neuronal damage are not well characterized. Here, the authors show that αS fibrils release soluble prefibrillar oligomeric species responsible for neurotoxicity in vitro.

    • Roberta Cascella
    • , Serene W. Chen
    •  & Cristina Cecchi
  • Article
    | Open Access

    Mutations in ENT3, encoded by SLC29A3, result in anaemia and erythroid hypoplasia, suggesting roles in erythropoiesis. Here the authors show that ENT3 acts as a lysosomal bile acid transporter, and mutation compromises taurine conjugated bile acid transport in erythroid progenitors leading to ER stress, and anaemia.

    • Avinash K. Persaud
    • , Sreenath Nair
    •  & Rajgopal Govindarajan
  • Article
    | Open Access

    Systemic AA amyloidosis is a protein misfolding disease caused by the formation of amyloid fibrils from serum amyloid A (SAA) protein. Here, the authors present the cryo-EM structures of AA amyloid fibrils isolated from mouse tissue and in vitro formed fibrils, which differ in their structures and they also show that the ex vivo fibrils are more resistant to proteolysis than the in vitro fibrils and propose that pathogenic amyloid fibrils might originate from proteolytic selection.

    • Akanksha Bansal
    • , Matthias Schmidt
    •  & Marcus Fändrich
  • Article
    | Open Access

    The Hsp70/Hsp40 system plays an important role in maintaining cellular proteostasis but so far it is not well understood how Hsp70 proteins are recruited to specific Hsp40 co-chaperones. Here, the authors combine biochemical and biophysical approaches to characterise the oligomeric mammalian Hsp40 DnaJB8. They identify an intra-oligomer DnaJB8 interaction between the N-terminal J-Domain and the C-terminal domain that occludes the J-Domain surface that binds Hsp70 and propose a model for DnaJB8-Hsp70 recruitment.

    • Bryan D. Ryder
    • , Irina Matlahov
    •  & Lukasz A. Joachimiak
  • Article
    | Open Access

    Coiled-coil protein origami (CCPO) is a strategy for the design of polyhedral cage-shaped protein folds based on coiled-coil (CC) dimer-forming peptides. Here, the authors show that CCPO proteins fold in a multistep process governed by the spatial distance between CC modules in the primary sequence and subsequent folding intermediates, which enables the use of identical CC modules for the CCPO tetrahedron design.

    • Jana Aupič
    • , Žiga Strmšek
    •  & Roman Jerala
  • Article
    | Open Access

    Spy is an ATP independent chaperone that can act as both a holdase and a foldase towards topologically simple substrates. Assessing the interaction of Spy and apoflavodoxin, a complex client, the authors show that Spy’s activity is substrate specific. Spy binds partially unfolded states of apoflavodoxin tightly, which limits the possibility of folding and converts Spy to a pure holdase.

    • Rishav Mitra
    • , Varun V. Gadkari
    •  & James C. A. Bardwell
  • Article
    | Open Access

    Systemic AL amyloidosis is a protein misfolding disease caused by the aggregation and fibrillation of immunoglobulin light chains (LCs). Here, the authors present the cryo-EM structures of λ3 LC-derived amyloid fibrils that were isolated from patient tissue and they observe structural breaks, where the two different fibril structures co-exist at different z-axial positions within the same fibril.

    • Lynn Radamaker
    • , Julian Baur
    •  & Marcus Fändrich
  • Article
    | Open Access

    p23 is a co-chaperone of Hsp90 but its mode of action is mechanistically not well understood. Here, the authors combine in vitro and yeast in vivo assays, biochemical measurements and NMR experiments to characterize p23 and identify two conserved helical elements in the intrinsically disordered C-terminal tail of p23 that together with the folded domain of p23 regulate the Hsp90 ATPase activity and affect the binding and maturation of Hsp90 clients.

    • Maximilian M. Biebl
    • , Abraham Lopez
    •  & Johannes Buchner
  • Article
    | Open Access

    Our understanding of the molecular mechanisms underlying pathological protein aggregation remains incomplete. Here, single molecule infrared nanospectroscopy (AFM-IR) offers insight into the structure of Aβ42 oligomeric and fibrillar species and their interaction with an aggregation inhibitor, paving the way for single molecule drug discovery studies.

    • Francesco Simone Ruggeri
    • , Johnny Habchi
    •  & Tuomas P. J. Knowles
  • Article
    | Open Access

    Existing methods for inflicting cellular heat shock are limited by the time delay in achieving the desired temperature and the spatial precision that can be achieved. Here the authors report a method to induce focused thermal protein damage using plasmonic silver nanoparticles.

    • Martin Mistrik
    • , Zdenek Skrott
    •  & Jiri Bartek
  • Article
    | Open Access

    ClpXP is the main ATP-dependent proteolytic complex in bacteria, is essential for maintaining cellular protein homeostasis and is also critical for bacterial pathogenesis. Here, the authors establish a functional link between ClpXP and trigger actor, a chaperone involved in the early stages of protein folding.

    • Kamran Rizzolo
    • , Angela Yeou Hsiung Yu
    •  & Walid A. Houry
  • Article
    | Open Access

    Most mitochondrial proteins are imported from the cytosol and must fold in the mitochondria. Here, the authors show that the mitochondrial protease LONP1 plays a critical role in the mtHSP70 chaperone system independently of its protease activity.

    • Chun-Shik Shin
    • , Shuxia Meng
    •  & David C. Chan
  • Article
    | Open Access

    Thiol-disulfide exchange is an extensively used reversible reaction in dynamic combinatorial chemistry, but usually requires long time to reach equilibrium. Here, the authors employ selenocystine as a catalyst of thiol-disulfide exchange at low temperatures and basic pH, and show that it can promote disulfide bond formation during folding of a scrambled RNase A.

    • Andrea Canal-Martín
    •  & Ruth Pérez-Fernández
  • Article
    | Open Access

    α1-Antitrypsin (AAT) is a 52 kDa serum glycoprotein, the misfolding and polymerisation of which is associated with COPD and liver disease. Here the authors demonstrate the use of high-resolution multidimensional solution-state NMR spectroscopy to characterise the structure and dynamics in solution of Z AAT purified directly from clinical patients.

    • Alistair M. Jagger
    • , Christopher A. Waudby
    •  & David A. Lomas
  • Article
    | Open Access

    Identifying factors that enable cells to induce a potent stress response to amyloid-like aggregation can provide further insight into the mechanism of stress regulation. Here, the authors express polyglutamine-expanded Huntingtin as a model disease protein in yeast cells and perform a genetic screen for chaperone factors that allow yeast cells to activate a potent stress response. They identify Sis1, an essential Hsp40 co-chaperone of Hsp70, as a critical sensor of proteotoxic stress and further show that both Sis1 and its mammalian homolog DnaJB6 regulate the magnitude of the cellular heat stress response, indicating that this mechanism is conserved.

    • Courtney L. Klaips
    • , Michael H. M. Gropp
    •  & F. Ulrich Hartl
  • Article
    | Open Access

    The analysis of biomolecular frustration yielded insights into several aspects of protein behavior. Here the authors describe a framework to efficiently quantify and localize biomolecular frustration within proteins at atomic resolution, and observe that drug specificity is correlated with a minimally frustrated binding pocket leading to a funneled binding landscape.

    • Mingchen Chen
    • , Xun Chen
    •  & Peter G. Wolynes
  • Article
    | Open Access

    Biochemistry combined with biophysical measurements and mathematical modeling offer insight into the mechanism by which the cotranslational chaperone, nascent polypeptide-associated complex (NAC), modulates substrate selection by signal recognition particle (SRP) and reduces aberrant, nonspecific targeting of ribosomes to the ER.

    • Hao-Hsuan Hsieh
    • , Jae Ho Lee
    •  & Shu-ou Shan
  • Article
    | Open Access

    Glaucoma is the leading cause of irreversible blindness affecting over 70 million people worldwide. Here, the authors show that inhibition of chronic ER stress-induced ATF4-CHOP-GADD34 signaling pathway rescues pathology in mouse models of glaucoma, thus suggesting a possible treatment strategy.

    • Ramesh B. Kasetti
    • , Pinkal D. Patel
    •  & Gulab S. Zode
  • Article
    | Open Access

    Disulfide bonds play critical roles in determining protein structure and function. Here, the authors show that fibrinogen exists in multiple disulfide-bonded states in human blood, and that these states change during fibrin polymerization and in response to fluid shear forces.

    • Diego Butera
    •  & Philip J. Hogg
  • Article
    | Open Access

    In vivo experiments and optical tweezers force-spectroscopy measurements assessing the co-translational folding of the G-domain from bacterial elongation factor G reveal a sequential folding pathway initiating from the C-terminus. These results suggest that protein folding and synthesis proceed in opposite directions.

    • Xiuqi Chen
    • , Nandakumar Rajasekaran
    •  & Christian M. Kaiser
  • Article
    | Open Access

    Mechanically stable specific heterodimerization formed with reversible bonds are used as a molecular anchorage in single-molecule force spectroscopy studies with unique mechanical properties. Here authors develop a variety of heterodimerization molecular systems with a range of mechanical stability from a set of recently engineered helix-heterotetramers.

    • Miao Yu
    • , Zhihai Zhao
    •  & Jie Yan
  • Article
    | Open Access

    Cystic fibrosis (CF) is a lethal genetic disease that is primarily caused by misfolding of the cystic fibrosis transmembrane conductance regulator (CFTR). Here authors show that disease-causing mutations located within the first nucleotide binding domain of CFTR have distinct effects on nascent polypeptides.

    • Hideki Shishido
    • , Jae Seok Yoon
    •  & William R. Skach
  • Article
    | Open Access

    Detection of amyloid beta deposits is often performed with fluorescent compounds that bind plaques. Here the authors develop turn-on chemiluminescent probes that bind amyloid beta plaques in vivo, and amplify the signal via chemiluminescence resonance energy transfer to the plaque-binding fluorescent molecule CRANAD-3.

    • Jing Yang
    • , Wei Yin
    •  & Chongzhao Ran
  • Article
    | Open Access

    ALS is a neurodegenerative disease characterized by loss of motor neurons. Here, the authors showed that reduced levels of the VSP35 subunit in the retromer complex is a conserved ALS feature and identified a new lead compound increasing retromer stability ameliorating the disease phenotype.

    • Luca Muzio
    • , Riccardo Sirtori
    •  & Gianvito Martino
  • Article
    | Open Access

    The ATPase SecA drives Sec-dependent protein translocation across the bacterial plasma membrane. Here, the authors combine kinetic translocation measurements with single-molecule force spectroscopy and demonstrate that the SecA motor generates mechanical force to unfold and translocate preproteins.

    • Riti Gupta
    • , Dmitri Toptygin
    •  & Christian M. Kaiser