1
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Pal S, Udgaonkar JB. Mutations of evolutionarily conserved aromatic residues suggest that misfolding of the mouse prion protein may commence in multiple ways. J Neurochem 2023; 167:696-710. [PMID: 37941487 DOI: 10.1111/jnc.16007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 11/10/2023]
Abstract
The misfolding of the mammalian prion protein from its α-helix rich cellular isoform to its β-sheet rich infectious isoform is associated with several neurodegenerative diseases. The determination of the structural mechanism by which misfolding commences, still remains an unsolved problem. In the current study, native-state hydrogen exchange coupled with mass spectrometry has revealed that the N state of the mouse prion protein (moPrP) at pH 4 is in dynamic equilibrium with multiple partially unfolded forms (PUFs) capable of initiating misfolding. Mutation of three evolutionarily conserved aromatic residues, Tyr168, Phe174, and Tyr217 present at the interface of the β2-α2 loop and the C-terminal end of α3 in the structured C-terminal domain of moPrP significantly destabilize the native state (N) of the protein. They also reduce the free energy differences between the N state and two PUFs identified as PUF1 and PUF2**. It is shown that PUF2** in which the β2-α2 loop and the C-terminal end of α3 are disordered, has the same stability as the previously identified PUF2*, but to have a very different structure. Misfolding can commence from both PUF1 and PUF2**, as it can from PUF2*. Hence, misfolding can commence and proceed in multiple ways from structurally distinct precursor conformations. The increased extents to which PUF1 and PUF2** are populated at equilibrium in the case of the mutant variants, greatly accelerate their misfolding. The results suggest that the three aromatic residues may have been evolutionarily selected to impede the misfolding of moPrP.
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Affiliation(s)
- Suman Pal
- Indian Institute of Science Education and Research Pune, Pune, India
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2
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L P Hosszu L, Sangar D, Batchelor M, Risse E, Hounslow AM, Collinge J, Waltho JP, Bieschke J. Loss of residues 119 - 136, including the first β-strand of human prion protein, generates an aggregation-competent partially "open" form. J Mol Biol 2023:168158. [PMID: 37244570 DOI: 10.1016/j.jmb.2023.168158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 05/29/2023]
Abstract
In prion replication, the cellular form of prion protein (PrPC) must undergo a full conformational transition to its disease-associated fibrillar form. Transmembrane forms of PrP have been implicated in this structural conversion. The cooperative unfolding of a structural core in PrPC presents a substantial energy barrier to prion formation, with membrane insertion and detachment of parts of PrP presenting a plausible route to its reduction. Here, we examined the removal of residues 119 - 136 of PrP, a region which includes the first β-strand and a substantial portion of the conserved hydrophobic region of PrP, a region which associates with the ER membrane, on the structure, stability and self-association of the folded domain of PrPC. We see an "open" native-like conformer with increased solvent exposure which fibrilises more readily than the native state. These data suggest a stepwise folding transition, which is initiated by the conformational switch to this "open" form of PrPC.
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Affiliation(s)
- Laszlo L P Hosszu
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK
| | - Daljit Sangar
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK
| | - Mark Batchelor
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK
| | - Emmanuel Risse
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK
| | - Andrea M Hounslow
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - John Collinge
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK
| | - Jonathan P Waltho
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK; Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Jan Bieschke
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, 33 Cleveland Street, London, W1W 7FF, UK.
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3
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Pal S, Udgaonkar JB. Evolutionarily Conserved Proline Residues Impede the Misfolding of the Mouse Prion Protein by Destabilizing an Aggregation-competent Partially Unfolded Form. J Mol Biol 2022; 434:167854. [PMID: 36228749 DOI: 10.1016/j.jmb.2022.167854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 10/04/2022] [Accepted: 10/04/2022] [Indexed: 11/06/2022]
Abstract
The misfolding of the prion protein has been linked to several neurodegenerative diseases. Despite extensive studies, the mechanism of the misfolding process remains poorly understood. The present study structurally delineates the role of the conserved proline residues present in the structured C-terminal domain of the mouse prion protein (moPrP) in the misfolding process. It is shown that mutation of these Pro residues to Ala leads to destabilization of the native (N) state, and also to rapid misfolding. Using hydrogen-deuterium exchange (HDX) studies coupled with mass spectrometry (MS), it has been shown that the N state of moPrP is in rapid equilibrium with a partially unfolded form (PUF2*) at pH 4. It has been shown that the Pro to Ala mutations make PUF2* energetically more accessible from the N state by stabilizing it relative to the unfolded (U) state. The apparent rate constant of misfolding is found to be linearly proportional to the extent to which PUF2* is populated in equilibrium with the N state, strongly indicating that misfolding commences from PUF2*. It has also been shown that the Pro residues restrict the boundary of the structural core of the misfolded oligomers. Overall, this study highlights how the conserved proline residues control misfolding of the prion protein by modulating the stability of the partially unfolded form from which misfolding commences.
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Affiliation(s)
- Suman Pal
- Indian Institute of Science Education and Research, Pune, India
| | - Jayant B Udgaonkar
- Indian Institute of Science Education and Research, Pune, India; National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India.
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4
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Bhagavatula H, Sarkar A, Santra B, Das A. Scan-Find-Scan-Model: Discrete Site-Targeted Suppressor Design Strategy for Amyloid-β. ACS Chem Neurosci 2022; 13:2191-2208. [PMID: 35767676 DOI: 10.1021/acschemneuro.2c00272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Alzheimer's disease is undoubtedly the most well-studied neurodegenerative disease. Consequently, the amyloid-β (Aβ) protein ranks at the top in terms of getting attention from the scientific community for structural property-based characterization. Even after decades of extensive research, there is existing volatility in terms of understanding and hence the effective tackling procedures against the disease that arises due to the lack of knowledge of both specific target- and site-specific drugs. Here, we develop a multidimensional approach based on the characterization of the common static-dynamic-thermodynamic trait of the monomeric protein, which efficiently identifies a small target sequence that contains an inherent tendency to misfold and consequently aggregate. The robustness of the identification of the target sequence comes with an abundance of a priori knowledge about the length and sequence of the target and hence guides toward effective designing of the target-specific drug with a very low probability of bottleneck and failure. Based on the target sequence information, we further identified a specific mutant that showed the maximum potential to act as a destabilizer of the monomeric protein as well as enormous success as an aggregation suppressor. We eventually tested the drug efficacy by estimating the extent of modulation of binding affinity existing within the fibrillar form of the Aβ protein due to a single-point mutation and hence provided a proof of concept of the entire protocol.
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Affiliation(s)
- Hasathi Bhagavatula
- Department of Biotechnology, Progressive Education Society's Modern College of Arts Science and Commerce, Shivajinagar, Pune 411005, India
| | - Archishman Sarkar
- School of Applied and Interdisciplinary Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja Subodh Chandra Mallick Road, Kolkata, West Bengal 700032, India
| | - Binit Santra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kalyanpur, Kanpur, Uttar Pradesh 208016, India
| | - Atanu Das
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, Maharashtra 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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5
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Sen S, Kumar H, Udgaonkar JB. Microsecond Dynamics During the Binding-induced Folding of an Intrinsically Disordered Protein. J Mol Biol 2021; 433:167254. [PMID: 34537237 DOI: 10.1016/j.jmb.2021.167254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/08/2021] [Accepted: 09/10/2021] [Indexed: 11/26/2022]
Abstract
Tau is an intrinsically disordered protein implicated in many neurodegenerative diseases. The repeat domain fragment of tau, tau-K18, is known to undergo a disorder to order transition in the presence of lipid micelles and vesicles, in which helices form in each of the repeat domains. Here, the mechanism of helical structure formation, induced by a phospholipid mimetic, sodium dodecyl sulfate (SDS) at sub-micellar concentrations, has been studied using multiple biophysical probes. A study of the conformational dynamics of the disordered state, using photoinduced electron transfer coupled to fluorescence correlation spectroscopy (PET-FCS) has indicated the presence of an intermediate state, I, in equilibrium with the unfolded state, U. The cooperative binding of the ligand (L), SDS, to I has been shown to induce the formation of a compact, helical intermediate (IL5) within the dead time (∼37 µs) of a continuous flow mixer. Quantitative analysis of the PET-FCS data and the ensemble microsecond kinetic data, suggests that the mechanism of induction of helical structure can be described by a U ↔ I ↔ IL5 ↔ FL5 mechanism, in which the final helical state, FL5, forms from IL5 with a time constant of 50-200 µs. Finally, it has been shown that the helical conformation is an aggregation-competent state that can directly form amyloid fibrils.
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Affiliation(s)
- Sreemantee Sen
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India; Indian Institute of Science Education and Research, Pune, Pashan, Pune 411 008, India
| | - Harish Kumar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India; Indian Institute of Science Education and Research, Pune, Pashan, Pune 411 008, India
| | - Jayant B Udgaonkar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India; Indian Institute of Science Education and Research, Pune, Pashan, Pune 411 008, India.
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6
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Bhate SH, Udgaonkar JB, Das R. Destabilization of polar interactions in the prion protein triggers misfolding and oligomerization. Protein Sci 2021; 30:2258-2271. [PMID: 34558139 DOI: 10.1002/pro.4188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 09/15/2021] [Accepted: 09/16/2021] [Indexed: 12/25/2022]
Abstract
The prion protein (PrP) misfolds and oligomerizes at pH 4 in the presence of physiological salt concentrations. Low pH and salt cause structural perturbations in the monomeric prion protein that lead to misfolding and oligomerization. However, the changes in stability within different regions of the PrP prior to oligomerization are poorly understood. In this study, we have characterized the local stability in PrP at high resolution using amide temperature coefficients (TC ) measured by nuclear magnetic resonance (NMR) spectroscopy. The local stability of PrP was investigated under native as well as oligomerizing conditions. We have also studied the rapidly oligomerizing PrP variant (Q216R) and the protective PrP variant (A6). We report that at low pH, salt destabilizes PrP at several polar residues, and the hydrogen bonds in helices α2 and α3 are weakened. In addition, salt changes the curvature of the α3 helix, which likely disrupts α2-α3 contacts and leads to oligomerization. These results are corroborated by the TC values of rapidly oligomerizing Q216R-PrP. The poly-alanine substitution in A6-PrP stabilizes α2, which prevents oligomerization. Altogether, these results highlight the importance of native polar interactions in determining the stability of PrP and reveal the structural disruptions in PrP that lead to misfolding and oligomerization.
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Affiliation(s)
- Suhas H Bhate
- National Centre for Biological Sciences, TIFR, Bangalore, India
| | - Jayant B Udgaonkar
- National Centre for Biological Sciences, TIFR, Bangalore, India.,Indian Institute for Science Education and Research, Pune, India
| | - Ranabir Das
- National Centre for Biological Sciences, TIFR, Bangalore, India
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7
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Bandyopadhyay A, Sannigrahi A, Chattopadhyay K. Membrane composition and lipid to protein ratio modulate amyloid kinetics of yeast prion protein. RSC Chem Biol 2021; 2:592-605. [PMID: 34458802 PMCID: PMC8341755 DOI: 10.1039/d0cb00203h] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 01/15/2021] [Indexed: 12/22/2022] Open
Abstract
Understanding of prion aggregation in a membrane environment may help to ameliorate neurodegenerative complications caused by the amyloid forms of prions. Here, we investigated the membrane binding-induced aggregation of yeast prion protein Sup35. Using the combination of fluorescence correlation spectroscopy (FCS) at single molecule resolution and other biophysical studies, we establish that lipid composition and lipid/protein ratio are key modulators of the aggregation kinetics of Sup35. In the presence of a zwitterionic membrane (DMPC), Sup35 exhibited novel biphasic aggregation kinetics at lipid/protein ratios ranging between 20 : 1 and 70 : 1 (termed here as the optimum lipid concentration, OLC). In ratios below (low lipid concentration, LLC) and above (ELC, excess lipid concentration) that range, the aggregation was found to be monophasic. In contrast, in the presence of negatively charged membranes, we did not observe any bi-phasic aggregation kinetics in the entire range of protein to lipid ratios. Our results provide a mechanistic description of the role that membrane concentration/composition-modulated aggregation may play in neurodegenerative diseases.
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Affiliation(s)
- Arnab Bandyopadhyay
- Structural Biology & Bio-Informatics Division, CSIR-Indian Institute of Chemical Biology 4, Raja S. C. Mullick Road Kolkata 700032 India
| | - Achinta Sannigrahi
- Structural Biology & Bio-Informatics Division, CSIR-Indian Institute of Chemical Biology 4, Raja S. C. Mullick Road Kolkata 700032 India
| | - Krishnananda Chattopadhyay
- Structural Biology & Bio-Informatics Division, CSIR-Indian Institute of Chemical Biology 4, Raja S. C. Mullick Road Kolkata 700032 India
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8
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Mondal B, Reddy G. A Transient Intermediate Populated in Prion Folding Leads to Domain Swapping. Biochemistry 2019; 59:114-124. [DOI: 10.1021/acs.biochem.9b00621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Balaka Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka India, 560012
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka India, 560012
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9
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Zhou S, Shi D, Liu X, Yao X, Da LT, Liu H. pH-Induced Misfolding Mechanism of Prion Protein: Insights from Microsecond-Accelerated Molecular Dynamics Simulations. ACS Chem Neurosci 2019; 10:2718-2729. [PMID: 31070897 DOI: 10.1021/acschemneuro.8b00582] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The conformational transition of prion protein (PrP) from a native form PrPC to a pathological isoform PrPSc is the main cause of a number of prion diseases in human and animals. Thus, understanding the molecular basis of conformational transition of PrP will be valuable for unveiling the etiology of PrP-related diseases. Here, to explore the potential misfolding mechanism of PrP under the acidic condition, which is known to promote PrP misfolding and trigger its aggregation, the conventional and accelerated molecular dynamics (MD) simulations combined with the Markov state model (MSM) analysis were performed. The conventional MD simulations reveal that, at an acidic pH, the globular domain of PrP is partially unfolded, particularly for the α2 C-terminus. Structural analysis of the key macrostates obtained by MSM indicates that the α2 C-terminus and the β2-α2 loop may serve as important sites for the pH-induced PrP misfolding. Meanwhile, the α1 may also participate in the pH-induced structural conversion by moving away from the α2-α3 subdomain. Notably, dynamical network analysis of the key metastable states indicates that the protonated H187 weakens the interactions between the α2 C-terminus, α1-β2 loop, and α2-α3 loop, leading these domains, especially the α2 C-terminus, to become unstable and to begin to misfold. Therefore, the α2 C-terminus plays a key role in the PrP misfolding process and serves as a potential site for drug targeting. Overall, our findings can deepen the understanding of the pathogenesis related to PrP and provide useful guidance for the future drug discovery.
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Affiliation(s)
- Shuangyan Zhou
- School of Pharmacy, Lanzhou University, Lanzhou 730000, China
- Chongqing Key Laboratory on Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
| | - Danfeng Shi
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Xuewei Liu
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
- State Key Laboratory of Quality Research in Chinese Medicine, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Taipa, Macau, China
| | - Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai JiaoTong University, Shanghai 200240, China
| | - Huanxiang Liu
- School of Pharmacy, Lanzhou University, Lanzhou 730000, China
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10
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Goluguri RR, Sen S, Udgaonkar J. Microsecond sub-domain motions and the folding and misfolding of the mouse prion protein. eLife 2019; 8:e44766. [PMID: 31025940 PMCID: PMC6516828 DOI: 10.7554/elife.44766] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Accepted: 04/25/2019] [Indexed: 12/29/2022] Open
Abstract
Protein aggregation appears to originate from partially unfolded conformations that are sampled through stochastic fluctuations of the native protein. It has been a challenge to characterize these fluctuations, under native like conditions. Here, the conformational dynamics of the full-length (23-231) mouse prion protein were studied under native conditions, using photoinduced electron transfer coupled to fluorescence correlation spectroscopy (PET-FCS). The slowest fluctuations could be associated with the folding of the unfolded state to an intermediate state, by the use of microsecond mixing experiments. The two faster fluctuations observed by PET-FCS, could be attributed to fluctuations within the native state ensemble. The addition of salt, which is known to initiate the aggregation of the protein, resulted in an enhancement in the time scale of fluctuations in the core of the protein. The results indicate the importance of native state dynamics in initiating the aggregation of proteins.
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Affiliation(s)
- Rama Reddy Goluguri
- National Centre for Biological SciencesTata Institute of Fundamental ResearchBengaluruIndia
| | - Sreemantee Sen
- National Centre for Biological SciencesTata Institute of Fundamental ResearchBengaluruIndia
| | - Jayant Udgaonkar
- National Centre for Biological SciencesTata Institute of Fundamental ResearchBengaluruIndia
- Indian Institute of Science Education and ResearchPuneIndia
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11
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Moulick R, Goluguri RR, Udgaonkar JB. Ruggedness in the Free Energy Landscape Dictates Misfolding of the Prion Protein. J Mol Biol 2019; 431:807-824. [DOI: 10.1016/j.jmb.2018.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/15/2018] [Accepted: 12/16/2018] [Indexed: 12/12/2022]
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12
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Benhaim M, Lee KK, Guttman M. Tracking Higher Order Protein Structure by Hydrogen-Deuterium Exchange Mass Spectrometry. Protein Pept Lett 2019; 26:16-26. [PMID: 30543159 PMCID: PMC6386625 DOI: 10.2174/0929866526666181212165037] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/30/2018] [Accepted: 11/17/2018] [Indexed: 12/27/2022]
Abstract
BACKGROUND Structural biology has provided a fundamental understanding of protein structure and mechanistic insight into their function. However, high-resolution structures alone are insufficient for a complete understanding of protein behavior. Higher energy conformations, conformational changes, and subtle structural fluctuations that underlie the proper function of proteins are often difficult to probe using traditional structural approaches. Hydrogen/Deuterium Exchange with Mass Spectrometry (HDX-MS) provides a way to probe the accessibility of backbone amide protons under native conditions, which reports on local structural dynamics of solution protein structure that can be used to track complex structural rearrangements that occur in the course of a protein's function. CONCLUSION In the last 20 years the advances in labeling techniques, sample preparation, instrumentation, and data analysis have enabled HDX to gain insights into very complex biological systems. Analysis of challenging targets such as membrane protein complexes is now feasible and the field is paving the way to the analysis of more and more complex systems.
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Affiliation(s)
- Mark Benhaim
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195 USA
| | - Kelly K. Lee
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195 USA
| | - Miklos Guttman
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195 USA
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13
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Kuzishchin YA, Martynov IL, Osipov EV, Samokhvalov PS, Chistyakov AA, Nabiev IR. Comparison of fluorescence excitation modes for cdse semi-conductor quantum dots used in medical research. BULLETIN OF RUSSIAN STATE MEDICAL UNIVERSITY 2018. [DOI: 10.24075/brsmu.2018.050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fluorescence spectroscopy is a powerful tool used in applied biological and medical research. Colloid semi-conductor quantum dots are promising fluorescent tags for simultaneous detection of different biopathogens. The techniques employing these tags can be improved by selecting the optimal modes for signal excitation and detection. The aim of the present work was to derive a mathematical expression to describe the signal-to-noise ratios in the pulsed and modulated excitation modes. Below, we compare these two modes of fluorescence excitation in ultralow quantities of quantum dots. We demonstrate that modulated excitation should be preferred for CdSe/ZnS quantum dots given that signal accumulation time is over 100 mc and the photosensor is exposed to background light of > 1 μW.
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Affiliation(s)
- Y. A. Kuzishchin
- Department of Physics of Micro- and Nanosystems, National Research Nuclear University MEPhI, Moscow, Russia
| | - I. L. Martynov
- Department of Physics of Micro- and Nanosystems, National Research Nuclear University MEPhI, Moscow, Russia
| | - E. V. Osipov
- Department of Physics of Micro- and Nanosystems, National Research Nuclear University MEPhI, Moscow, Russia
| | - P. S. Samokhvalov
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI, Moscow, Russia
| | - A. A. Chistyakov
- Department of Physics of Micro- and Nanosystems, National Research Nuclear University MEPhI, Moscow, Russia
| | - I. R. Nabiev
- Laboratory of Nano-Bioengineering, National Research Nuclear University MEPhI, Moscow, Russia
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14
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Sengupta I, Udgaonkar JB. Structural mechanisms of oligomer and amyloid fibril formation by the prion protein. Chem Commun (Camb) 2018; 54:6230-6242. [PMID: 29789820 DOI: 10.1039/c8cc03053g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Misfolding and aggregation of the prion protein is responsible for multiple neurodegenerative diseases. Works from several laboratories on folding of both the WT and multiple pathogenic mutant variants of the prion protein have identified several structurally dissimilar intermediates, which might be potential precursors to misfolding and aggregation. The misfolded aggregates themselves are morphologically distinct, critically dependent on the solution conditions under which they are prepared, but always β-sheet rich. Despite the lack of an atomic resolution structure of the infectious pathogenic agent in prion diseases, several low resolution models have identified the β-sheet rich core of the aggregates formed in vitro, to lie in the α2-α3 subdomain of the prion protein, albeit with local stabilities that vary with the type of aggregate. This feature article describes recent advances in the investigation of in vitro prion protein aggregation using multiple spectroscopic probes, with particular focus on (1) identifying aggregation-prone conformations of the monomeric protein, (2) conditions which trigger misfolding and oligomerization, (3) the mechanism of misfolding and aggregation, and (4) the structure of the misfolded intermediates and final aggregates.
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Affiliation(s)
- Ishita Sengupta
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
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15
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Conformation Polymorphism of Polyglutamine Proteins. Trends Biochem Sci 2018; 43:424-435. [PMID: 29636213 DOI: 10.1016/j.tibs.2018.03.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/05/2018] [Accepted: 03/12/2018] [Indexed: 01/29/2023]
Abstract
Expanded polyglutamine (polyQ) stretches within endogenous proteins cause at least nine human diseases. The structural basis of polyQ pathogenesis is the key to understanding fundamental mechanisms of these diseases, but it remains unclear and controversial due to a lack of polyQ protein structures at the single-atom level. Various hypotheses have been proposed to explain the structure-cytotoxicity relationship of pathogenic proteins with polyQ expansion, largely based on indirect evidence. Here we review these hypotheses and their supporting evidence, along with additional insights from recent structural biology and chemical biology studies, with a focus on Huntingtin (HTT), the most extensively studied polyQ disease protein. Lastly, we propose potential novel strategies that may further clarify the conformation-cytotoxicity relationship of polyQ proteins.
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16
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Sen S, Goluguri RR, Udgaonkar JB. A Dry Transition State More Compact Than the Native State Is Stabilized by Non-Native Interactions during the Unfolding of a Small Protein. Biochemistry 2017; 56:3699-3703. [DOI: 10.1021/acs.biochem.7b00388] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Sreemantee Sen
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
| | - Rama Reddy Goluguri
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
| | - Jayant B. Udgaonkar
- National Centre for Biological
Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India
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Honda RP, Kuwata K. The native state of prion protein (PrP) directly inhibits formation of PrP-amyloid fibrils in vitro. Sci Rep 2017; 7:562. [PMID: 28373719 PMCID: PMC5429628 DOI: 10.1038/s41598-017-00710-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 03/08/2017] [Indexed: 11/25/2022] Open
Abstract
The conversion of globular proteins into amyloid fibrils is associated with a wide variety of human diseases. One example is the prion protein (PrP), which adopts an α-helical structure in the native state but its amyloid form is implicated in the pathogenesis of prion diseases. Previous evidence has suggested that destabilization of the native state promotes amyloid formation, but the underlying mechanism remains unknown. In this study, we report that the native state of PrP serves as a potent inhibitor in the formation of PrP amyloid fibrils. By monitoring the time courses of thioflavin T fluorescence, the kinetics of amyloid formation was studied in vitro under various concentrations of pre-formed amyloid, monomer, and denaturant. Quantitative analysis of the kinetic data using various models of enzyme kinetics suggested that the native state of PrP is either an uncompetitive or noncompetitive inhibitor of amyloid formation. This study highlights the significant role of the native state in inhibiting amyloid formation, which provides new insights into the pathogenesis of misfolding diseases.
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Affiliation(s)
- Ryo P Honda
- Department of Molecular Pathobiochemistry, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
| | - Kazuo Kuwata
- United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan. .,Department of Gene and Development, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
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