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Montagne A, Nikolakopoulou AM, Zhao Z, Sagare AP, Si G, Lazic D, Barnes SR, Daianu M, Ramanathan A, Go A, Lawson EJ, Wang Y, Mack WJ, Thompson PM, Schneider JA, Varkey J, Langen R, Mullins E, Jacobs RE, Zlokovic BV. Retraction Note: Pericyte degeneration causes white matter dysfunction in the mouse central nervous system. Nat Med 2024; 30:1215. [PMID: 38580816 PMCID: PMC11036445 DOI: 10.1038/s41591-024-02935-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2024]
Affiliation(s)
- Axel Montagne
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Angeliki M Nikolakopoulou
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Zhen Zhao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Abhay P Sagare
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Gabriel Si
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Divna Lazic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Neurobiology, Institute for Biological Research, University of Belgrade, Belgrade, Republic of Serbia
| | - Samuel R Barnes
- Biological Imaging Center, Beckman Institute, California Institute of Technology, Pasadena, California, USA
| | - Madelaine Daianu
- Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, University of Southern California, Marina del Rey, California, USA
| | - Anita Ramanathan
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Ariel Go
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Erica J Lawson
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Yaoming Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - William J Mack
- Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Paul M Thompson
- Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, University of Southern California, Marina del Rey, California, USA
| | - Julie A Schneider
- Alzheimer's Disease Center, Rush University Medical Center, Chicago, Illinois, USA
| | - Jobin Varkey
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Eric Mullins
- Division of Hematology and Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Russell E Jacobs
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Biological Imaging Center, Beckman Institute, California Institute of Technology, Pasadena, California, USA
| | - Berislav V Zlokovic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
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Pandey NK, Varkey J, Ajayan A, George G, Chen J, Langen R. Fluorescent protein tagging promotes phase separation and alters the aggregation pathway of huntingtin exon-1. J Biol Chem 2024; 300:105585. [PMID: 38141760 PMCID: PMC10825056 DOI: 10.1016/j.jbc.2023.105585] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 12/11/2023] [Accepted: 12/13/2023] [Indexed: 12/25/2023] Open
Abstract
Fluorescent protein tags are convenient tools for tracking the aggregation states of amyloidogenic or phase separating proteins, but the effect of the tags is often not well understood. Here, we investigated the impact of a C-terminal red fluorescent protein (RFP) tag on the phase separation of huntingtin exon-1 (Httex1), an N-terminal portion of the huntingtin protein that aggregates in Huntington's disease. We found that the RFP-tagged Httex1 rapidly formed micron-sized, phase separated states in the presence of a crowding agent. The formed structures had a rounded appearance and were highly dynamic according to electron paramagnetic resonance and fluorescence recovery after photobleaching, suggesting that the phase separated state was largely liquid in nature. Remarkably, the untagged protein did not undergo any detectable liquid condensate formation under the same conditions. In addition to strongly promoting liquid-liquid phase separation, the RFP tag also facilitated fibril formation, as the tag-dependent liquid condensates rapidly underwent a liquid-to-solid transition. The rate of fibril formation under these conditions was significantly faster than that of the untagged protein. When expressed in cells, the RFP-tagged Httex1 formed larger aggregates with different antibody staining patterns compared to untagged Httex1. Collectively, these data reveal that the addition of a fluorescent protein tag significantly impacts liquid and solid phase separations of Httex1 in vitro and leads to altered aggregation in cells. Considering that the tagged Httex1 is commonly used to study the mechanisms of Httex1 misfolding and toxicity, our findings highlight the importance to validate the conclusions with untagged protein.
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Affiliation(s)
- Nitin K Pandey
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jobin Varkey
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Anakha Ajayan
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Gincy George
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jeannie Chen
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Ralf Langen
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
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Bravo-Arredondo JM, Venkataraman R, Varkey J, Isas JM, Situ AJ, Xu H, Chen J, Ulmer TS, Langen R. Molecular basis of Q-length selectivity for the MW1 antibody-huntingtin interaction. J Biol Chem 2023; 299:104616. [PMID: 36931390 PMCID: PMC10124945 DOI: 10.1016/j.jbc.2023.104616] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 03/08/2023] [Accepted: 03/09/2023] [Indexed: 03/17/2023] Open
Abstract
Huntington's disease is caused by a polyglutamine (polyQ) expansion in the huntingtin protein. Huntingtin exon 1 (Httex1), as well as other naturally occurring N-terminal huntingtin fragments with expanded polyQ are prone to aggregation, forming potentially cytotoxic oligomers and fibrils. Antibodies and other N-terminal huntingtin binders are widely explored as biomarkers and possible aggregation-inhibiting therapeutics. A monoclonal antibody, MW1, is known to preferentially bind to huntingtin fragments with expanded polyQ lengths, but the molecular basis of the polyQ length specificity remains poorly understood. Using solution NMR, EPR, and other biophysical methods, we investigated the structural features of the Httex1-MW1 interaction. Rather than recognizing residual α-helical structure, which is promoted by expanded Q-lengths, MW1 caused the formation of a new, non-native, conformation in which the entire polyQ is largely extended. This non-native polyQ structure allowed the formation of large mixed Httex1-MW1 multimers (600-2900 kD), when Httex1 with pathogenic Q-length (Q46) was used. We propose that these multivalent, entropically favored interactions, are available only to proteins with longer Q-lengths and represent a major factor governing the Q-length preference of MW1. The present study reveals that it is possible to target proteins with longer Q-lengths without having to stabilize a natively favored conformation. Such mechanisms could be exploited in the design of other Q-length specific binders.
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Affiliation(s)
- Jose M Bravo-Arredondo
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Rajashree Venkataraman
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jobin Varkey
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jose Mario Isas
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Alan J Situ
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Hui Xu
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jeannie Chen
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Tobias S Ulmer
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Ralf Langen
- Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
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Kegulian NC, Langen R, Moradian-Oldak J. The Dynamic Interactions of a Multitargeting Domain in Ameloblastin Protein with Amelogenin and Membrane. Int J Mol Sci 2023; 24:3484. [PMID: 36834897 PMCID: PMC9966149 DOI: 10.3390/ijms24043484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/28/2023] [Accepted: 02/06/2023] [Indexed: 02/12/2023] Open
Abstract
The enamel matrix protein Ameloblastin (Ambn) has critical physiological functions, including regulation of mineral formation, cell differentiation, and cell-matrix adhesion. We investigated localized structural changes in Ambn during its interactions with its targets. We performed biophysical assays and used liposomes as a cell membrane model. The xAB2N and AB2 peptides were rationally designed to encompass regions of Ambn that contained self-assembly and helix-containing membrane-binding motifs. Electron paramagnetic resonance (EPR) on spin-labeled peptides showed localized structural gains in the presence of liposomes, amelogenin (Amel), and Ambn. Vesicle clearance and leakage assays indicated that peptide-membrane interactions were independent from peptide self-association. Tryptophan fluorescence and EPR showed competition between Ambn-Amel and Ambn-membrane interactions. We demonstrate localized structural changes in Ambn upon interaction with different targets via a multitargeting domain, spanning residues 57 to 90 of mouse Ambn. Structural changes of Ambn following its interaction with different targets have relevant implications for the multifunctionality of Ambn in enamel formation.
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Affiliation(s)
- Natalie C. Kegulian
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Ralf Langen
- Department of Neuroscience and Physiology, Department of Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Department of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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Chongtham A, Isas JM, Pandey NK, Rawat A, Yoo JH, Mastro T, Kennedy MB, Langen R, Khoshnan A. Amplification of neurotoxic HTTex1 assemblies in human neurons. Neurobiol Dis 2021; 159:105517. [PMID: 34563643 DOI: 10.1016/j.nbd.2021.105517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/24/2021] [Accepted: 09/21/2021] [Indexed: 11/25/2022] Open
Abstract
Huntington's disease (HD) is a genetically inherited neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) repeat in the exon-1 of huntingtin protein (HTT). The expanded polyQ enhances the amyloidogenic propensity of HTT exon 1 (HTTex1), which forms a heterogeneous mixture of assemblies with a broad neurotoxicity spectrum. While predominantly intracellular, monomeric and aggregated mutant HTT species are also present in the cerebrospinal fluids of HD patients, however, their biological properties are not well understood. To explore the role of extracellular mutant HTT in aggregation and toxicity, we investigated the uptake and amplification of recombinant HTTex1 assemblies in cell culture models. We find that small HTTex1 fibrils preferentially enter human neurons and trigger the amplification of neurotoxic assemblies; astrocytes or epithelial cells are not permissive. The amplification of HTTex1 in neurons depletes endogenous HTT protein with non-pathogenic polyQ repeat, activates apoptotic caspase-3 pathway and induces nuclear fragmentation. Using a panel of novel monoclonal antibodies and genetic mutation, we identified epitopes within the N-terminal 17 amino acids and proline-rich domain of HTTex1 to be critical in neural uptake and amplification. Synaptosome preparations from the brain homogenates of HD mice also contain mutant HTT species, which enter neurons and behave similar to small recombinant HTTex1 fibrils. These studies suggest that amyloidogenic extracellular mutant HTTex1 assemblies may preferentially enter neurons, propagate and promote neurodegeneration.
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Affiliation(s)
| | - J Mario Isas
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Nitin K Pandey
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Anoop Rawat
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Jung Hyun Yoo
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Tara Mastro
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Mary B Kennedy
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Ali Khoshnan
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA.
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Mario Isas J, Pandey NK, Xu H, Teranishi K, Okada AK, Fultz EK, Rawat A, Applebaum A, Meier F, Chen J, Langen R, Siemer AB. Huntingtin fibrils with different toxicity, structure, and seeding potential can be interconverted. Nat Commun 2021; 12:4272. [PMID: 34257293 PMCID: PMC8277859 DOI: 10.1038/s41467-021-24411-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 06/17/2021] [Indexed: 11/09/2022] Open
Abstract
The first exon of the huntingtin protein (HTTex1) important in Huntington's disease (HD) can form cross-β fibrils of varying toxicity. We find that the difference between these fibrils is the degree of entanglement and dynamics of the C-terminal proline-rich domain (PRD) in a mechanism analogous to polyproline film formation. In contrast to fibril strains found for other cross-β fibrils, these HTTex1 fibril types can be interconverted. This is because the structure of their polyQ fibril core remains unchanged. Further, we find that more toxic fibrils of low entanglement have higher affinities for protein interactors and are more effective seeds for recombinant HTTex1 and HTTex1 in cells. Together these data show how the structure of a framing sequence at the surface of a fibril can modulate seeding, protein-protein interactions, and thereby toxicity in neurodegenerative disease.
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Affiliation(s)
- J Mario Isas
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Nitin K Pandey
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Hui Xu
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Kazuki Teranishi
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Alan K Okada
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.,Department of Emergency Medicine, Regions Hospital, St. Paul, MN, USA
| | - Ellisa K Fultz
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Anoop Rawat
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Anise Applebaum
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Franziska Meier
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Jeannie Chen
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Ralf Langen
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
| | - Ansgar B Siemer
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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Varkey J, Zhang J, Kim J, George G, He G, Belov G, Langen R, Wang X. An Amphipathic Alpha-Helix Domain from Poliovirus 2C Protein Tubulate Lipid Vesicles. Viruses 2020; 12:v12121466. [PMID: 33353144 PMCID: PMC7766222 DOI: 10.3390/v12121466] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 02/01/2023] Open
Abstract
Positive-strand RNA viruses universally remodel host intracellular membranes to form membrane-bound viral replication complexes, where viral offspring RNAs are synthesized. In the majority of cases, viral replication proteins are targeted to and play critical roles in the modulation of the designated organelle membranes. Many viral replication proteins do not have transmembrane domains, but contain single or multiple amphipathic alpha-helices. It has been conventionally recognized that these helices serve as an anchor for viral replication protein to be associated with membranes. We report here that a peptide representing the amphipathic α-helix at the N-terminus of the poliovirus 2C protein not only binds to liposomes, but also remodels spherical liposomes into tubules. The membrane remodeling ability of this amphipathic alpha-helix is similar to that recognized in other amphipathic alpha-helices from cellular proteins involved in membrane remodeling, such as BAR domain proteins. Mutations affecting the hydrophobic face of the amphipathic alpha-helix severely compromised membrane remodeling of vesicles with physiologically relevant phospholipid composition. These mutations also affected the ability of poliovirus to form plaques indicative of reduced viral replication, further underscoring the importance of membrane remodeling by the amphipathic alpha-helix in possible relation to the formation of viral replication complexes.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
| | - Jiantao Zhang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
| | - Junghyun Kim
- Virginia-Maryland College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA; (J.K.); (G.B.)
| | - Gincy George
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
| | - Guijuan He
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
| | - George Belov
- Virginia-Maryland College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA; (J.K.); (G.B.)
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
- Correspondence: (R.L.); (X.W.); Tel.: +1-323-442-1323 (R.L.); +1-540-231-1868 (X.W.)
| | - Xiaofeng Wang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
- Correspondence: (R.L.); (X.W.); Tel.: +1-323-442-1323 (R.L.); +1-540-231-1868 (X.W.)
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Falk AS, Bravo-Arredondo JM, Varkey J, Pacheco S, Langen R, Siemer AB. Structural Model of the Proline-Rich Domain of Huntingtin Exon-1 Fibrils. Biophys J 2020; 119:2019-2028. [PMID: 33096080 PMCID: PMC7732765 DOI: 10.1016/j.bpj.2020.10.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/17/2020] [Accepted: 10/13/2020] [Indexed: 01/09/2023] Open
Abstract
Huntington's disease is a heritable neurodegenerative disease that is caused by a CAG expansion in the first exon of the huntingtin gene. This expansion results in an elongated polyglutamine domain that increases the propensity of huntingtin exon-1 to form cross-β fibrils. Although the polyglutamine domain is important for fibril formation, the dynamic, C-terminal proline-rich domain (PRD) of huntingtin exon-1 makes up a large fraction of the fibril surface. Because potential fibril toxicity has to be mediated by interactions of the fibril surface with its cellular environment, we wanted to model the conformational space adopted by the PRD. We ran 800-ns long molecular dynamics simulations of the PRD using an explicit water model optimized for intrinsically disordered proteins. These simulations accurately predicted our previous solid-state NMR data and newly acquired electron paramagnetic resonance double electron-electron resonance distances, lending confidence in their accuracy. The simulations show that the PRD generally forms an imperfect polyproline (polyP) II helical conformation. The two polyP regions within the PRD stay in a polyP II helix for most of the simulation, whereas occasional kinks in the proline-rich linker region cause an overall bend in the PRD structure. The dihedral angles of the glycine at the end of the second polyP region are very variable, effectively decoupling the highly dynamic 12 C-terminal residues from the rest of the PRD.
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Affiliation(s)
- Alexander S Falk
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - José M Bravo-Arredondo
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Jobin Varkey
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Sayuri Pacheco
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Ralf Langen
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Ansgar B Siemer
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California.
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Lo CH, Pandey NK, Lim CKW, Ding Z, Tao M, Thomas DD, Langen R, Sachs JN. Discovery of Small Molecule Inhibitors of Huntingtin Exon 1 Aggregation by FRET-Based High-Throughput Screening in Living Cells. ACS Chem Neurosci 2020; 11:2286-2295. [PMID: 32568514 DOI: 10.1021/acschemneuro.0c00226] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Huntington's disease (HD) is the most common inherited neurodegenerative disorder and one of the nine polyglutamine (polyQ) diseases. HD is characterized by the pathological aggregation of the misfolded huntingtin exon 1 protein (Httex1) with abnormally long polyQ expansion due to genetic mutation. While there is currently no effective treatment for HD, inhibition of aggregate formation represents a direct approach in mediating the toxicity associated with Httex1 misfolding. To exploit this therapeutic window, we engineered two fluorescence resonance energy transfer (FRET) based biosensors that monitor the aggregation of Httex1 with different expanded Q-lengths (Q39 and Q72) in living cells. These FRET biosensors, together with a high-precision fluorescence lifetime detection platform, enable high-throughput screening of small molecules that target Httex1 aggregation. We found six small molecules that decreased the FRET of the biosensors and reduced Httex1-Q72-induced neuronal cytotoxicity in N2a cells with nanomolar potency. Using advanced SPR and EPR techniques, we confirmed that the compounds directly bind to Httex1 fibrils and inhibit aggregate formation. This strategy in targeting the Httex1 aggregates can be applicable to other proteins involved in polyQ related diseases.
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Affiliation(s)
- Chih Hung Lo
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Nitin K. Pandey
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
| | - Colin Kin-Wye Lim
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Zhipeng Ding
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Meixin Tao
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, United States
- Photonic Pharma LLC, Minneapolis, Minnesota 55410, United States
| | - Ralf Langen
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, United States
| | - Jonathan N. Sachs
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
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10
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Ko J, Isas JM, Sabbaugh A, Yoo JH, Pandey NK, Chongtham A, Ladinsky M, Wu WL, Rohweder H, Weiss A, Macdonald D, Munoz-Sanjuan I, Langen R, Patterson PH, Khoshnan A. Identification of distinct conformations associated with monomers and fibril assemblies of mutant huntingtin. Hum Mol Genet 2019; 27:2330-2343. [PMID: 29912367 DOI: 10.1093/hmg/ddy141] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 04/12/2018] [Accepted: 04/16/2018] [Indexed: 11/14/2022] Open
Abstract
The N-terminal fragments of mutant huntingtin (mHTT) misfold and assemble into oligomers, which ultimately bundle into insoluble fibrils. Conformations unique to various assemblies of mHTT remain unknown. Knowledge on the half-life of various multimeric structures of mHTT is also scarce. Using a panel of four new antibodies named PHP1-4, we have identified new conformations in monomers and assembled structures of mHTT. PHP1 and PHP2 bind to epitopes within the proline-rich domain (PRD), whereas PHP3 and PHP4 interact with motifs formed at the junction of polyglutamine (polyQ) and polyproline (polyP) repeats of HTT. The PHP1- and PHP2-reactive epitopes are exposed in fibrils of mHTT exon1 (mHTTx1) generated from recombinant proteins and mHTT assemblies, which progressively accumulate in the nuclei, cell bodies and neuropils in the brains of HD mouse models. Notably, electron microscopic examination of brain sections of HD mice revealed that PHP1- and PHP2-reactive mHTT assemblies are present in myelin sheath and in vesicle-like structures. Moreover, PHP1 and PHP2 antibodies block seeding and subsequent fibril assembly of mHTTx1 in vitro and in a cell culture model of HD. PHP3 and PHP4 bind to epitopes in full-length and N-terminal fragments of monomeric mHTT and binding diminishes as the mHTTx1 assembles into fibrils. Interestingly, PHP3 and PHP4 also prevent the aggregation of mHTTx1 in vitro highlighting a regulatory function for the polyQ-polyP motifs. These newly detected conformations may affect fibril assembly, stability and intercellular transport of mHTT.
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Affiliation(s)
- Jan Ko
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - J Mario Isas
- Zilka Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Adam Sabbaugh
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Jung Hyun Yoo
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Nitin K Pandey
- Zilka Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | | | - Mark Ladinsky
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Wei-Li Wu
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | | | - Andreas Weiss
- Evotec, Manfred Eigen Campus, Hamburg 22419, Germany
| | | | | | - Ralf Langen
- Zilka Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | | | - Ali Khoshnan
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
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11
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Levine ZA, Teranishi K, Okada AK, Langen R, Shea JE. The Mitochondrial Peptide Humanin Targets but Does Not Denature Amyloid Oligomers in Type II Diabetes. J Am Chem Soc 2019; 141:14168-14179. [DOI: 10.1021/jacs.9b04995] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Zachary A. Levine
- Department of Pathology, Yale School of Medicine, New Haven, Connecticut 06520, United States
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, Connecticut 06520, United States
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12
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Tao M, Pandey NK, Barnes R, Han S, Langen R. Structure of Membrane-Bound Huntingtin Exon 1 Reveals Membrane Interaction and Aggregation Mechanisms. Structure 2019; 27:1570-1580.e4. [PMID: 31466833 DOI: 10.1016/j.str.2019.08.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/23/2019] [Accepted: 08/09/2019] [Indexed: 02/08/2023]
Abstract
Huntington's disease is caused by a polyQ expansion in the first exon of huntingtin (Httex1). Membrane interaction of huntingtin is of physiological and pathological relevance. Using electron paramagnetic resonance and Overhauser dynamic nuclear polarization, we find that the N-terminal residues 3-13 of wild-type Httex1(Q25) form a membrane-bound, amphipathic α helix. This helix is positioned in the interfacial region, where it is sensitive to membrane curvature and electrostatic interactions with head-group charges. Residues 14-22, which contain the first five residues of the polyQ region, are in a transition region that remains in the interfacial region without taking up a stable, α-helical structure. The remaining C-terminal portion is solvent exposed. The phosphomimetic S13D/S16D mutations, which are known to protect from toxicity, inhibit membrane binding and attenuate membrane-mediated aggregation of mutant Httex1(Q46) due to electrostatic repulsion. Targeting the N-terminal membrane anchor using post-translational modifications or specific binders could be a potential means to reduce aggregation and toxicity in vivo.
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Affiliation(s)
- Meixin Tao
- Department of Neuroscience and Physiology, Department of Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Nitin K Pandey
- Department of Neuroscience and Physiology, Department of Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Ryan Barnes
- Department of Chemistry and Biochemistry, Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Songi Han
- Department of Chemistry and Biochemistry, Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ralf Langen
- Department of Neuroscience and Physiology, Department of Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
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13
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Rovere M, Powers AE, Jiang H, Pitino JC, Fonseca-Ornelas L, Patel DS, Achille A, Langen R, Varkey J, Bartels T. E46K-like α-synuclein mutants increase lipid interactions and disrupt membrane selectivity. J Biol Chem 2019; 294:9799-9812. [PMID: 31048377 PMCID: PMC6597829 DOI: 10.1074/jbc.ra118.006551] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 05/01/2019] [Indexed: 01/01/2023] Open
Abstract
Parkinson's disease (PD) is one of the most common neurodegenerative disorders, and both genetic and histopathological evidence have implicated the ubiquitous presynaptic protein α-synuclein (αSyn) in its pathogenesis. Recent work has investigated how disrupting αSyn's interaction with membranes triggers trafficking defects, cellular stress, and apoptosis. Special interest has been devoted to a series of mutants exacerbating the effects of the E46K mutation (associated with autosomal dominant PD) through homologous Glu-to-Lys substitutions in αSyn's N-terminal region (i.e. E35K and E61K). Such E46K-like mutants have been shown to cause dopaminergic neuron loss and severe but L-DOPA-responsive motor defects in mouse overexpression models, presenting enormous translational potential for PD and other "synucleinopathies." In this work, using a variety of biophysical techniques, we characterize the molecular pathology of E46K-like αSyn mutants by studying their structure and membrane-binding and remodeling abilities. We find that, although a slight increase in the mutants' avidity for synaptic vesicle-like membranes can be detected, most of their deleterious effects are connected to their complete disruption of αSyn's curvature selectivity. Indiscriminate binding can shift αSyn's subcellular localization away from its physiological interactants at the synaptic bouton toward trafficking vesicles and organelles, as observed in E46K-like cellular and murine models, as well as in human pathology. In conclusion, our findings suggest that a loss of curvature selectivity, rather than increased membrane affinity, could be the critical dyshomeostasis in synucleinopathies.
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Affiliation(s)
- Matteo Rovere
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Alex E Powers
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Haiyang Jiang
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Julia C Pitino
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Luis Fonseca-Ornelas
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Dushyant S Patel
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Alessandro Achille
- the Department of Computer Science, University of California, Los Angeles, California 90095
| | - Ralf Langen
- the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and
| | - Jobin Varkey
- the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and
| | - Tim Bartels
- From the Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115,
- the Dementia Research Institute, University College London, London WC1E 6BT, United Kingdom
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14
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Vasquez-Montes V, Vargas-Uribe M, Pandey NK, Rodnin MV, Langen R, Ladokhin AS. Lipid-modulation of membrane insertion and refolding of the apoptotic inhibitor Bcl-xL. Biochim Biophys Acta Proteins Proteom 2019; 1867:691-700. [PMID: 31004798 DOI: 10.1016/j.bbapap.2019.04.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 04/16/2019] [Indexed: 02/07/2023]
Abstract
Bcl-xL is a member of the Bcl-2 family of apoptotic regulators, responsible for inhibiting the permeabilization of the mitochondrial outer membrane, and a promising anti-cancer target. Bcl-xL exists in the following conformations, each believed to play a role in the inhibition of apoptosis: (a) a soluble folded conformation, (b) a membrane-anchored (by its C-terminal α8 helix) form, which retains the same fold as in solution and (c) refolded membrane-inserted conformations, for which no structural data are available. Previous studies established that in the cell Bcl-xL exists in a dynamic equilibrium between soluble and membranous states, however, no direct evidence exists in support of either anchored or inserted conformation of the membranous state in vivo. In this in vitro study, we employed a combination of fluorescence and EPR spectroscopy to characterize structural features of the bilayer-inserted conformation of Bcl-xL and the lipid modulation of its membrane insertion transition. Our results indicate that the core hydrophobic helix α6 inserts into the bilayer without adopting a transmembrane orientation. This insertion disrupts the packing of Bcl-xL and releases the regulatory N-terminal BH4 domain (α1) from the rest of the protein structure. Our data demonstrate that both insertion and refolding of Bcl-xL are modulated by lipid composition, which brings the apparent pKa of insertion to the threshold of physiological pH. We hypothesize that conformational rearrangements associated with the bilayer insertion of Bcl-xL result in its switching to a so-called non-canonical mode of apoptotic inhibition. Presented results suggest that the alteration in lipid composition before and during apoptosis can serve as an additional factor regulating the permeabilization of the mitochondrial outer membrane.
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Affiliation(s)
- Victor Vasquez-Montes
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Mauricio Vargas-Uribe
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Nitin K Pandey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Mykola V Rodnin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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15
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Fenton CG, Webster JM, Martin CS, Fareed S, Wehmeyer C, Mackie H, Jones R, Seabright AP, Lewis JW, Lai YC, Goodyear CS, Jones SW, Cooper MS, Lavery GG, Langen R, Raza K, Hardy RS. Therapeutic glucocorticoids prevent bone loss but drive muscle wasting when administered in chronic polyarthritis. Arthritis Res Ther 2019; 21:182. [PMID: 31370858 PMCID: PMC6676537 DOI: 10.1186/s13075-019-1962-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 07/22/2019] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Patients with rheumatoid arthritis (RA) experience extra-articular manifestations including osteoporosis and muscle wasting, which closely associate with severity of disease. Whilst therapeutic glucocorticoids (GCs) reduce inflammation in RA, their actions on muscle and bone metabolism in the context of chronic inflammation remain unclear. We utilised the TNF-tg model of chronic polyarthritis to ascertain the impact of therapeutic GCs on bone and muscle homeostasis in the context of systemic inflammation. METHODS TNF-tg and wild-type (WT) animals received either vehicle or the GC corticosterone (100 μg/ml) in drinking water at onset of arthritis. Arthritis severity and clinical parameters were measured, serum collected for ELISA and muscle and bone biopsies collected for μCT, histology and mRNA analysis. In vivo findings were examined in primary cultures of osteoblasts, osteoclasts and myotubes. RESULTS TNF-tg mice receiving GCs showed protection from inflammatory bone loss, characterised by a reduction in serum markers of bone resorption, osteoclast numbers and osteoclast activity. In contrast, muscle wasting was markedly increased in WT and TNF-tg animals receiving GCs, independently of inflammation. This was characterised by a reduction in muscle weight and fibre size, and an induction in anti-anabolic and catabolic signalling. CONCLUSIONS This study demonstrates that when given in early onset chronic polyarthritis, oral GCs partially protect against inflammatory bone loss, but induce marked muscle wasting. These results suggest that in patients with inflammatory arthritis receiving GCs, the development of interventions to manage deleterious side effects in muscle should be prioritised.
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Affiliation(s)
- C. G. Fenton
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK
| | - J. M. Webster
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK ,Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
| | - C. S. Martin
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK
| | - S. Fareed
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK
| | - C. Wehmeyer
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK
| | - H. Mackie
- 0000 0001 2193 314Xgrid.8756.cCentre of Immunobiology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - R. Jones
- 0000 0004 1936 7486grid.6572.6MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Birmingham, Birmingham, UK
| | - A. P. Seabright
- 0000 0004 1936 7486grid.6572.6School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - J. W. Lewis
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Birmingham, Birmingham, UK
| | - Y. C. Lai
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - C. S. Goodyear
- 0000 0001 2193 314Xgrid.8756.cCentre of Immunobiology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - S. W Jones
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK
| | - M. S. Cooper
- 0000 0004 1936 834Xgrid.1013.3ANZAC Research Institute, University of Sydney, Sydney, Australia
| | - G. G. Lavery
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK ,Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK
| | - R. Langen
- 0000 0001 0481 6099grid.5012.6Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands
| | - K. Raza
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK ,grid.412919.6Sandwell and West Birmingham Hospitals NHS Trust, Birmingham, UK
| | - R. S. Hardy
- 0000 0004 1936 7486grid.6572.6Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6MRC Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Birmingham, Birmingham, UK ,0000 0004 1936 7486grid.6572.6Institute of Clinical Sciences, University of Birmingham, Birmingham, UK
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16
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Bravo-Arredondo JM, Kegulian NC, Schmidt T, Pandey NK, Situ AJ, Ulmer TS, Langen R. The folding equilibrium of huntingtin exon 1 monomer depends on its polyglutamine tract. J Biol Chem 2018; 293:19613-19623. [PMID: 30315108 DOI: 10.1074/jbc.ra118.004808] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 10/05/2018] [Indexed: 11/06/2022] Open
Abstract
Expansion of the polyglutamine (polyQ) tract in exon 1 of the huntingtin protein (Httex1) leads to Huntington's disease resulting in fatal neurodegeneration. However, it remains poorly understood how polyQ expansions alter protein structure and cause toxicity. Using CD, EPR, and NMR spectroscopy, we found here that monomeric Httex1 consists of two co-existing structural states whose ratio is determined by polyQ tract length. We observed that short Q-lengths favor a largely random-coil state, whereas long Q-lengths increase the proportion of a predominantly α-helical state. We also note that by following a mobility gradient, Httex1 α-helical conformation is restricted to the N-terminal N17 region and to the N-terminal portion of the adjoining polyQ tract. Structuring in both regions was interdependent and likely stabilized by tertiary contacts. Although little helicity was present in N17 alone, each Gln residue in Httex1 enhanced helix stability by 0.03-0.05 kcal/mol, causing a pronounced preference for the α-helical state at pathological Q-lengths. The Q-length-dependent structuring and rigidification could be mimicked in proteins with shorter Q-lengths by a decrease in temperature, indicating that lower temperatures similarly stabilize N17 and polyQ intramolecular contacts. The more rigid α-helical state of Httex1 with an expanded polyQ tract is expected to alter interactions with cellular proteins and modulate the toxic Httex1 misfolding process. We propose that the polyQ-dependent shift in the structural equilibrium may enable future therapeutic strategies that specifically target Httex1 with toxic Q-lengths.
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Affiliation(s)
- Jose M Bravo-Arredondo
- From the Departments of Physiology and Neuroscience and.,the Facultad de Ciencias Básicas, Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Calzada Apizaquito S/N, 90300 Apizaco, Tlaxcala, Mexico
| | - Natalie C Kegulian
- Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Thomas Schmidt
- Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | | | - Alan J Situ
- From the Departments of Physiology and Neuroscience and
| | - Tobias S Ulmer
- From the Departments of Physiology and Neuroscience and.,Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
| | - Ralf Langen
- From the Departments of Physiology and Neuroscience and .,Biochemistry and Molecular Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and
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17
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Taylor JR, Fernandez DJ, Thornton SM, Skeate JG, Lühen KP, Da Silva DM, Langen R, Kast WM. Heterotetrameric annexin A2/S100A10 (A2t) is essential for oncogenic human papillomavirus trafficking and capsid disassembly, and protects virions from lysosomal degradation. Sci Rep 2018; 8:11642. [PMID: 30076379 PMCID: PMC6076308 DOI: 10.1038/s41598-018-30051-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/23/2018] [Indexed: 02/07/2023] Open
Abstract
Human papillomavirus (HPV) entry into epithelial cells is independent of canonical endocytic pathways. Upon interaction with host cells, HPV establishes infection by traversing through an endocytic pathway that is clathrin- and caveolin-independent, but dependent on the annexin A2/S100A10 heterotetramer (A2t). We examined the contribution of monomeric annexin A2 (AnxA2) vs. A2t in HPV infection and endocytosis, and further characterized the role of these molecules in protein trafficking. We specifically show that cell surface A2t is not required for HPV attachment, and in the absence of A2t virion internalization remains clathrin-independent. Without A2t, viral progression from early endosomes to multivesicular endosomes is significantly inhibited, capsid uncoating is dramatically reduced, and lysosomal degradation of HPV is accelerated. Furthermore, we present evidence that AnxA2 forms a complex with CD63, a known mediator of HPV trafficking. Overall, the observed reduction in infection is less significant in the absence of S100A10 alone compared to full A2t, supporting an independent role for monomeric AnxA2. More broadly, we show that successful infection by multiple oncogenic HPV types is dependent on A2t. These findings suggest that A2t is a central mediator of high-risk HPV intracellular trafficking post-entry and pre-viral uncoating.
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Affiliation(s)
- Julia R Taylor
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, CA, USA
| | - Daniel J Fernandez
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, CA, USA
| | - Shantaé M Thornton
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, CA, USA
| | - Joseph G Skeate
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, CA, USA
| | - Kim P Lühen
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA
| | - Diane M Da Silva
- Department of Obstetrics & Gynecology, University of Southern California, Los Angeles, CA, USA
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA, USA
| | - W Martin Kast
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, CA, USA.
- Department of Obstetrics & Gynecology, University of Southern California, Los Angeles, CA, USA.
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA.
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18
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Rawat A, Langen R, Varkey J. Membranes as modulators of amyloid protein misfolding and target of toxicity. Biochim Biophys Acta Biomembr 2018; 1860:1863-1875. [PMID: 29702073 DOI: 10.1016/j.bbamem.2018.04.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 04/19/2018] [Accepted: 04/19/2018] [Indexed: 12/15/2022]
Abstract
Abnormal protein aggregation is a hallmark of various human diseases. α-Synuclein, a protein implicated in Parkinson's disease, is found in aggregated form within Lewy bodies that are characteristically observed in the brains of PD patients. Similarly, deposits of aggregated human islet amyloid polypeptide (IAPP) are found in the pancreatic islets in individuals with type 2 diabetes mellitus. Significant number of studies have focused on how monomeric, disaggregated proteins transition into various amyloid structures leading to identification of a vast number of aggregation promoting molecules and processes over the years. Inasmuch as these factors likely enhance the formation of toxic, misfolded species, they might act as risk factors in disease. Cellular membranes, and particularly certain lipids, are considered to be among the major players for aggregation of α-synuclein and IAPP, and membranes might also be the target of toxicity. Past studies have utilized an array of biophysical tools, both in vitro and in vivo, to expound the membrane-mediated aggregation. Here, we focus on membrane interaction of α-synuclein and IAPP, and how various kinds of membranes catalyze or modulate the aggregation of these proteins and how, in turn, these proteins disrupt membrane integrity, both in vitro and in vivo. The membrane interaction and subsequent aggregation has been briefly contrasted to aggregation of α-synuclein and IAPP in solution. This article is part of a Special Issue entitled: Protein Aggregation and Misfolding at the Cell Membrane Interface edited by Ayyalusamy Ramamoorthy.
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Affiliation(s)
- Anoop Rawat
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, United States
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, United States.
| | - Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, United States.
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19
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Montagne A, Nikolakopoulou AM, Zhao Z, Sagare AP, Si G, Lazic D, Barnes SR, Daianu M, Ramanathan A, Go A, Lawson EJ, Wang Y, Mack WJ, Thompson PM, Schneider JA, Varkey J, Langen R, Mullins E, Jacobs RE, Zlokovic BV. Pericyte degeneration causes white matter dysfunction in the mouse central nervous system. Nat Med 2018; 24:326-337. [PMID: 29400711 PMCID: PMC5840035 DOI: 10.1038/nm.4482] [Citation(s) in RCA: 254] [Impact Index Per Article: 42.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 01/04/2018] [Indexed: 02/07/2023]
Abstract
Diffuse white-matter disease associated with small-vessel disease and dementia is prevalent in the elderly. The biological mechanisms, however, remain elusive. Using pericyte-deficient mice, magnetic resonance imaging, viral-based tract-tracing, and behavior and tissue analysis, we found that pericyte degeneration disrupted white-matter microcirculation, resulting in an accumulation of toxic blood-derived fibrin(ogen) deposits and blood-flow reductions, which triggered a loss of myelin, axons and oligodendrocytes. This disrupted brain circuits, leading to white-matter functional deficits before neuronal loss occurs. Fibrinogen and fibrin fibrils initiated autophagy-dependent cell death in oligodendrocyte and pericyte cultures, whereas pharmacological and genetic manipulations of systemic fibrinogen levels in pericyte-deficient, but not control mice, influenced the degree of white-matter fibrin(ogen) deposition, pericyte degeneration, vascular pathology and white-matter changes. Thus, our data indicate that pericytes control white-matter structure and function, which has implications for the pathogenesis and treatment of human white-matter disease associated with small-vessel disease.
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Affiliation(s)
- Axel Montagne
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Angeliki M. Nikolakopoulou
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Zhen Zhao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Abhay P. Sagare
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Gabriel Si
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Divna Lazic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Neurobiology, Institute for Biological Research, University of Belgrade, Belgrade, Republic of Serbia
| | - Samuel R. Barnes
- Biological Imaging Center, Beckman Institute, California Institute of Technology, Pasadena, CA 91101, USA
| | - Madelaine Daianu
- Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, University of Southern California, Marina del Rey, CA 90292, USA
| | - Anita Ramanathan
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Ariel Go
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Erica J. Lawson
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Yaoming Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - William J. Mack
- Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Paul M. Thompson
- Imaging Genetics Center, Mark & Mary Stevens Neuroimaging & Informatics Institute, University of Southern California, Marina del Rey, CA 90292, USA
| | - Julie A. Schneider
- Alzheimer's Disease Center, Rush University Medical Center, Chicago, IL 60612, USA
| | - Jobin Varkey
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Eric Mullins
- Division of Hematology and Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH 45229-3039
| | - Russell E. Jacobs
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Biological Imaging Center, Beckman Institute, California Institute of Technology, Pasadena, CA 91101, USA
| | - Berislav V. Zlokovic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA
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20
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Pandey NK, Isas JM, Rawat A, Lee RV, Langen J, Pandey P, Langen R. The 17-residue-long N terminus in huntingtin controls stepwise aggregation in solution and on membranes via different mechanisms. J Biol Chem 2018; 293:2597-2605. [PMID: 29282287 PMCID: PMC5818184 DOI: 10.1074/jbc.m117.813667] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 12/19/2017] [Indexed: 01/05/2023] Open
Abstract
Aggregation of huntingtin protein arising from expanded polyglutamine (polyQ) sequences in the exon-1 region of mutant huntingtin plays a central role in the pathogenesis of Huntington's disease. The huntingtin aggregation pathways are of therapeutic and diagnostic interest, but obtaining critical information from the physiologically relevant htt exon-1 (Httex1) protein has been challenging. Using biophysical techniques and an expression and purification protocol that generates clean, monomeric Httex1, we identified and mapped three distinct aggregation pathways: 1) unseeded in solution; 2) seeded in solution; and 3) membrane-mediated. In solution, aggregation proceeded in a highly stepwise manner, in which the individual domains (N terminus containing 17 amino acids (N17), polyQ, and proline-rich domain (PRD)) become ordered at very different rates. The aggregation was initiated by an early oligomer requiring a pathogenic, expanded Gln length and N17 α-helix formation. In the second phase, β-sheet forms in the polyQ. The slowest step is the final structural maturation of the PRD. This stepwise mechanism could be bypassed by seeding, which potently accelerated aggregation and was a prerequisite for prion-like spreading in vivo Remarkably, membranes could catalyze aggregation even more potently than seeds, in a process that caused significant membrane damage. The N17 governed membrane-mediated aggregation by anchoring Httex1 to the membrane, enhancing local concentration and promoting collision via two-dimensional diffusion. Considering its central roles in solution and in membrane-mediated aggregation, the N17 represents an attractive target for inhibiting multiple pathways. Our approach should help evaluate such inhibitors and identify diagnostic markers for the misfolded forms identified here.
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Affiliation(s)
- Nitin K Pandey
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - J Mario Isas
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Anoop Rawat
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Rachel V Lee
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Jennifer Langen
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Priyatama Pandey
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Ralf Langen
- From the Departments of Physiology and Neuroscience and of Biochemistry and Molecular Medicine. Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
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21
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Langen R. Molecular Mechanisms of Membrane Remodeling. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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22
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Cervantes Cortes SA, Isas JM, Kirstein J, Langen R, Siemer AB. Structural Characterization of the Mechanism of Aggregation and Disaggregation of Huntingtin. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.2369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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23
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Varkey J, Langen R. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR. J Magn Reson 2017; 280:127-139. [PMID: 28579098 PMCID: PMC5461824 DOI: 10.1016/j.jmr.2017.02.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/18/2017] [Accepted: 02/18/2017] [Indexed: 06/07/2023]
Abstract
The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single protein can generate different type of membrane curvatures using specific conformations for specific membrane structures and how EPR is a versatile tool well-suited to analyze subtle alterations in structures under such modifying conditions which otherwise would have been difficult using other biophysical tools.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, United States.
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, United States.
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24
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Fisette O, Päslack C, Barnes R, Isas JM, Langen R, Heyden M, Han S, Schäfer LV. Hydration Dynamics of a Peripheral Membrane Protein. J Am Chem Soc 2016; 138:11526-35. [PMID: 27548572 DOI: 10.1021/jacs.6b07005] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Water dynamics in the hydration shell of the peripheral membrane protein annexin B12 were studied using MD simulations and Overhauser DNP-enhanced NMR. We show that retardation of water motions near phospholipid bilayers is extended by the presence of a membrane-bound protein, up to around 10 Å above that protein. Near the membrane surface, electrostatic interactions with the lipid head groups strongly slow down water dynamics, whereas protein-induced water retardation is weaker and dominates only at distances beyond 10 Å from the membrane surface. The results can be understood from a simple model based on additive contributions from the membrane and the protein to the activation free energy barriers of water diffusion next to the biomolecular surfaces. Furthermore, analysis of the intermolecular vibrations of the water network reveals that retarded water motions near the membrane shift the vibrational modes to higher frequencies, which we used to identify an entropy gradient from the membrane surface toward the bulk water. Our results have implications for processes that take place at lipid membrane surfaces, including molecular recognition, binding, and protein-protein interactions.
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Affiliation(s)
- Olivier Fisette
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University , 44780 Bochum, Germany
| | - Christopher Päslack
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University , 44780 Bochum, Germany.,Max-Planck Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany
| | - Ryan Barnes
- Department of Chemistry and Biochemistry and Department of Chemical Engineering, University of California, Santa Barbara , Santa Barbara, California 93106, United States
| | - J Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California 90089, United States
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California 90089, United States
| | - Matthias Heyden
- Max-Planck Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany
| | - Songi Han
- Department of Chemistry and Biochemistry and Department of Chemical Engineering, University of California, Santa Barbara , Santa Barbara, California 93106, United States
| | - Lars V Schäfer
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University , 44780 Bochum, Germany
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25
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Okada AK, Teranishi K, Isas JM, Bedrood S, Chow RH, Langen R. Diabetic Risk Factors Promote Islet Amyloid Polypeptide Misfolding by a Common, Membrane-mediated Mechanism. Sci Rep 2016; 6:31094. [PMID: 27531121 PMCID: PMC4987648 DOI: 10.1038/srep31094] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 07/14/2016] [Indexed: 12/14/2022] Open
Abstract
The current diabetes epidemic is associated with a diverse set of risk factors including obesity and exposure to plastics. Notably, significant elevations of negatively charged amphiphilic molecules are observed in obesity (e.g. free fatty acids and phosphatidic acid) and plastics exposure (monophthalate esters). It remains unclear whether these factors share pathogenic mechanisms and whether links exist with islet amyloid polypeptide (IAPP) misfolding, a process central to β-cell dysfunction and death. Using a combination of fluorescence, circular dichroism and electron microscopy, we show that phosphatidic acid, oleic acid, and the phthalate metabolite MBzP partition into neutral membranes and enhance IAPP misfolding. The elevation of negative charge density caused by the presence of the risk factor molecules stabilizes a common membrane-bound α-helical intermediate that, in turn, facilitates IAPP misfolding. This shared mechanism points to a critical role for the membrane-bound intermediate in disease pathogenesis, making it a potential target for therapeutic intervention.
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Affiliation(s)
- Alan K Okada
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
| | - Kazuki Teranishi
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
| | - J Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
| | - Sahar Bedrood
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Robert H Chow
- Department of Physiology and Biophysics, Keck School of Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
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26
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Kegulian NC, Isas MJ, Chung SS, Pandey NK, Bravo JM, Langen R. Conformational Shifts in Huntingtin Exon 1 Monomer are Dependent on Temperature and Polyglutamine Length. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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27
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Pandey NK, Mario Isas J, Langen R. Studies on Domain Specific Aggregation Behavior of Huntingtin Exon1. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Levine ZA, Okada A, Teranishi K, Langen R, Shea JE. Reducing IAPP Aggregation with Mitochondrial Humanin Peptides; Results from Simulations and Experiments. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Dearborn AD, Wall JS, Cheng N, Heymann JB, Kajava AV, Varkey J, Langen R, Steven AC. α-Synuclein Amyloid Fibrils with Two Entwined, Asymmetrically Associated Protofibrils. J Biol Chem 2015; 291:2310-8. [PMID: 26644467 DOI: 10.1074/jbc.m115.698787] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Indexed: 11/06/2022] Open
Abstract
Parkinson disease and other progressive neurodegenerative conditions are characterized by the intracerebral presence of Lewy bodies, containing amyloid fibrils of α-synuclein. We used cryo-electron microscopy and scanning transmission electron microscopy (STEM) to study in vitro-assembled fibrils. These fibrils are highly polymorphic. Focusing on twisting fibrils with an inter-crossover spacing of 77 nm, our reconstructions showed them to consist of paired protofibrils. STEM mass per length data gave one subunit per 0.47 nm axial rise per protofibril, consistent with a superpleated β-structure. The STEM images show two thread-like densities running along each of these fibrils, which we interpret as ladders of metal ions. These threads confirmed the two-protofibril architecture of the 77-nm twisting fibrils and allowed us to identify this morphotype in STEM micrographs. Some other, but not all, fibril morphotypes also exhibit dense threads, implying that they also present a putative metal binding site. We propose a molecular model for the protofibril and suggest that polymorphic variant fibrils have different numbers of protofibrils that are associated differently.
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Affiliation(s)
- Altaira D Dearborn
- From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Joseph S Wall
- the Department of Biology, Brookhaven National Laboratory, Upton, New York 19973
| | - Naiqian Cheng
- From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - J Bernard Heymann
- From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Andrey V Kajava
- the Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier, Montpellier 34172, France, the University ITMO, Institute of Bioengineering, 197101 St. Petersburg, Russia
| | - Jobin Varkey
- the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and Karunya University, Coimbatore, Tamil Nadu 641 114, India
| | - Ralf Langen
- the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and
| | - Alasdair C Steven
- From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892,
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30
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Ambroso MR, Haworth IS, Langen R. Structural Characterization of Membrane-Curving Proteins: Site-Directed Spin Labeling, EPR, and Computational Refinement. Methods Enzymol 2015; 564:259-88. [PMID: 26477254 DOI: 10.1016/bs.mie.2015.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Endocytosis and other membrane remodeling processes require the coordinated generation of different membrane shapes. Proteins capable of manipulating lipid bilayers mediate these events using mechanisms that are not fully understood. Progress is limited by the small number of structures solved for proteins bound to different membrane shapes and tools capable of resolving such information. However, recent studies have shown site-directed spin labeling (SDSL) in combination with electron paramagnetic resonance (EPR) to be capable of obtaining high-resolution structural information for proteins bound to different membrane shapes. This technique can be applied to proteins with no known structure or proteins with structures known in solution. By refining the data obtained by EPR with computational modeling, 3D structures or structural models of membrane-bound proteins can be generated. In this chapter, we highlight the basic considerations and steps required to investigate the structures of membrane-bound proteins using SDSL, EPR, and computational refinement.
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Affiliation(s)
- Mark R Ambroso
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA
| | - Ian S Haworth
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California, USA
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California, USA.
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31
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Abstract
Measurement of distances between spin labels using electron paramagnetic resonance with the double electron-electron resonance (DEER) technique is an important method for evaluation of biomolecular structures. Computation of interlabel distances is of value for experimental planning, validation of known structures using DEER-measured distances, and determination of theoretical data for comparison with experiment. This requires steps of building labels at two defined sites on proteins, DNA or RNA; calculation of allowable label conformers based on rotation around torsional angles; computation of pairwise interlabel distances on a per conformer basis; and calculation of an average distance between the two label ensembles. We have described and validated two programs for this purpose: NASNOX, which permits computation of distances between R5 labels on DNA or RNA; and PRONOX, which similarly computes distances between R1 labels on proteins. However, these programs are limited to a specific single label and single target types. Therefore, we have developed a program, which we refer to as ALLNOX (Addition of Labels and Linkers), which permits addition of any label to any site on any target. The main principle in the program is to break the molecular system into a "label," a "linker," and a "target." The user can upload a "label" with any chemistry, define a "linker" based on a SMILES-like string, and then define the "target" site. The flexibility of ALLNOX facilitates theoretical evaluation of labels prior to synthesis and accommodates evaluation of experimental data in biochemical complexes containing multiple molecular types.
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Affiliation(s)
- Kathleen N Beasley
- Department of Pharmacology & Pharmaceutical Sciences, University of Southern California, Los Angeles, California, USA
| | - Brian T Sutch
- Department of Pharmacology & Pharmaceutical Sciences, University of Southern California, Los Angeles, California, USA
| | - Ma'mon M Hatmal
- Department of Laboratory Medical Sciences, Faculty of Allied Health Sciences, Hashemite University, Zarqa, Jordan
| | - Ralf Langen
- Department of Biochemistry, University of Southern California, Los Angeles, California, USA
| | - Peter Z Qin
- Department of Chemistry and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Ian S Haworth
- Department of Pharmacology & Pharmaceutical Sciences, University of Southern California, Los Angeles, California, USA; Department of Biochemistry, University of Southern California, Los Angeles, California, USA.
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32
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Kegulian NC, Sankhagowit S, Apostolidou M, Jayasinghe SA, Malmstadt N, Butler PC, Langen R. Membrane Curvature-sensing and Curvature-inducing Activity of Islet Amyloid Polypeptide and Its Implications for Membrane Disruption. J Biol Chem 2015; 290:25782-93. [PMID: 26283787 DOI: 10.1074/jbc.m115.659797] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Indexed: 11/06/2022] Open
Abstract
Islet amyloid polypeptide (IAPP) is a 37-amino acid amyloid protein intimately associated with pancreatic islet β-cell dysfunction and death in type II diabetes. In this study, we combine spectroscopic methods and microscopy to investigate α-helical IAPP-membrane interactions. Using light scattering and fluorescence microscopy, we observe that larger vesicles become smaller upon treatment with human or rat IAPP. Electron microscopy shows the formation of various highly curved structures such as tubules or smaller vesicles in a membrane-remodeling process, and spectrofluorometric detection of vesicle leakage shows disruption of membrane integrity. This effect is stronger for human IAPP than for the less toxic rat IAPP. From CD spectra in the presence of different-sized vesicles, we also uncover the membrane curvature-sensing ability of IAPP and find that it transitions from inducing to sensing membrane curvature when lipid negative charge is decreased. Our in vivo EM images of immunogold-labeled rat IAPP and human IAPP show both forms to localize to mitochondrial cristae, which contain not only locally curved membranes but also phosphatidylethanolamine and cardiolipin, lipids with high spontaneous negative curvature. Disruption of membrane integrity by induction of membrane curvature could apply more broadly to other amyloid proteins and be responsible for membrane damage observed in other amyloid diseases as well.
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Affiliation(s)
- Natalie C Kegulian
- From the Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Shalene Sankhagowit
- the Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, and
| | - Melania Apostolidou
- From the Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Sajith A Jayasinghe
- From the Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Noah Malmstadt
- the Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, and
| | - Peter C Butler
- the Larry Hillblom Islet Research Center, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Ralf Langen
- From the Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033,
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Abstract
Amyloid-like fibrils formed by huntingtin exon-1 (htt_ex1) are a hallmark of Huntington's disease (HD). The structure of these fibrils is unknown, and determining their structure is an important step toward understanding the misfolding processes that cause HD. In HD, a polyglutamine (polyQ) domain in htt_ex1 is expanded to a degree that it gains the ability to form aggregates comprising the core of the resulting fibrils. Despite the simplicity of this polyQ sequence, the structure of htt_ex1 fibrils has been difficult to determine. This study provides a detailed structural investigation of fibrils formed by htt_ex1 using solid-state nuclear magnetic resonance (NMR) spectroscopy. We show that the polyQ domain of htt_ex1 forms the static amyloid core similar to polyQ model peptides. The Gln residues of this domain exist in two distinct conformations that are found in separate domains or monomers but are relatively close in space. The rest of htt_ex1 is relatively dynamic on an NMR time scale, especially the proline-rich C-terminus, which we found to be in a polyproline II helical and random coil conformation. We observed a similar dynamic C-terminus in a soluble form of htt_ex1, indicating that the conformation of this part of htt_ex1 is not changed upon its aggregation into an amyloid fibril. From these data, we propose a bottlebrush model for the fibrils formed by htt_ex1. In this model, the polyQ domains form the center and the proline-rich domains the bristles of the bottlebrush.
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Affiliation(s)
- J Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
| | - Ansgar B Siemer
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, 1501 San Pablo Street, Los Angeles, California 90033, United States
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34
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Darrow MC, Sergeeva OA, Isas JM, Galaz-Montoya JG, King JA, Langen R, Schmid MF, Chiu W. Structural Mechanisms of Mutant Huntingtin Aggregation Suppression by the Synthetic Chaperonin-like CCT5 Complex Explained by Cryoelectron Tomography. J Biol Chem 2015; 290:17451-61. [PMID: 25995452 DOI: 10.1074/jbc.m115.655373] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Indexed: 11/06/2022] Open
Abstract
Huntington disease, a neurodegenerative disorder characterized by functional deficits and loss of striatal neurons, is linked to an expanded and unstable CAG trinucleotide repeat in the huntingtin gene (HTT). This DNA sequence translates to a polyglutamine repeat in the protein product, leading to mutant huntingtin (mHTT) protein aggregation. The aggregation of mHTT is inhibited in vitro and in vivo by the TCP-1 ring complex (TRiC) chaperonin. Recently, a novel complex comprised of a single type of TRiC subunit has been reported to inhibit mHTT aggregation. Specifically, the purified CCT5 homo-oligomer complex, when compared with TRiC, has a similar structure, ATP use, and substrate refolding activity, and, importantly, it also inhibits mHTT aggregation. Using an aggregation suppression assay and cryoelectron tomography coupled with a novel computational classification method, we uncover the interactions between the synthetic CCT5 complex (∼ 1 MDa) and aggregates of mutant huntingtin exon 1 containing 46 glutamines (mHTTQ46-Ex1). We find that, in a similar fashion to TRiC, synthetic CCT5 complex caps mHTT fibrils at their tips and encapsulates mHTT oligomers, providing a structural description of the inhibition of mHTTQ46-Ex1 by CCT5 complex and a shared mechanism of mHTT inhibition between TRiC chaperonin and the CCT5 complex: cap and contain.
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Affiliation(s)
- Michele C Darrow
- From the National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Oksana A Sergeeva
- the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and
| | - Jose M Isas
- the Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Jesús G Galaz-Montoya
- From the National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Jonathan A King
- the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and
| | - Ralf Langen
- the Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Michael F Schmid
- From the National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Wah Chiu
- From the National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030,
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35
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Fodale V, Kegulian NC, Verani M, Cariulo C, Azzollini L, Petricca L, Daldin M, Boggio R, Padova A, Kuhn R, Pacifici R, Macdonald D, Schoenfeld RC, Park H, Isas JM, Langen R, Weiss A, Caricasole A. Polyglutamine- and temperature-dependent conformational rigidity in mutant huntingtin revealed by immunoassays and circular dichroism spectroscopy. PLoS One 2014; 9:e112262. [PMID: 25464275 PMCID: PMC4251833 DOI: 10.1371/journal.pone.0112262] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 10/06/2014] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND In Huntington's disease, expansion of a CAG triplet repeat occurs in exon 1 of the huntingtin gene (HTT), resulting in a protein bearing>35 polyglutamine residues whose N-terminal fragments display a high propensity to misfold and aggregate. Recent data demonstrate that polyglutamine expansion results in conformational changes in the huntingtin protein (HTT), which likely influence its biological and biophysical properties. Developing assays to characterize and measure these conformational changes in isolated proteins and biological samples would advance the testing of novel therapeutic approaches aimed at correcting mutant HTT misfolding. Time-resolved Förster energy transfer (TR-FRET)-based assays represent high-throughput, homogeneous, sensitive immunoassays widely employed for the quantification of proteins of interest. TR-FRET is extremely sensitive to small distances and can therefore provide conformational information based on detection of exposure and relative position of epitopes present on the target protein as recognized by selective antibodies. We have previously reported TR-FRET assays to quantify HTT proteins based on the use of antibodies specific for different amino-terminal HTT epitopes. Here, we investigate the possibility of interrogating HTT protein conformation using these assays. METHODOLOGY/PRINCIPAL FINDINGS By performing TR-FRET measurements on the same samples (purified recombinant proteins or lysates from cells expressing HTT fragments or full length protein) at different temperatures, we have discovered a temperature-dependent, reversible, polyglutamine-dependent conformational change of wild type and expanded mutant HTT proteins. Circular dichroism spectroscopy confirms the temperature and polyglutamine-dependent change in HTT structure, revealing an effect of polyglutamine length and of temperature on the alpha-helical content of the protein. CONCLUSIONS/SIGNIFICANCE The temperature- and polyglutamine-dependent effects observed with TR-FRET on HTT proteins represent a simple, scalable, quantitative and sensitive assay to identify genetic and pharmacological modulators of mutant HTT conformation, and potentially to assess the relevance of conformational changes during onset and progression of Huntington's disease.
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Affiliation(s)
| | - Natalie C. Kegulian
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | | | | | | | | | | | | | | | | | - Robert Pacifici
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Douglas Macdonald
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Ryan C. Schoenfeld
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - Hyunsun Park
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
| | - J. Mario Isas
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Ralf Langen
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- * E-mail: (RL); (AW); (AC)
| | - Andreas Weiss
- IRBM Promidis, Pomezia, Rome, Italy
- * E-mail: (RL); (AW); (AC)
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36
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Lai Y, Kim S, Varkey J, Lou X, Song JK, Diao J, Langen R, Shin YK. Nonaggregated α-synuclein influences SNARE-dependent vesicle docking via membrane binding. Biochemistry 2014; 53:3889-96. [PMID: 24884175 PMCID: PMC4075992 DOI: 10.1021/bi5002536] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
α-Synuclein
(α-Syn), a major component of Lewy body
that is considered as the hallmark of Parkinson’s disease (PD),
has been implicated in neuroexocytosis. Overexpression of α-Syn
decreases the neurotransmitter release. However, the mechanism by
which α-Syn buildup inhibits the neurotransmitter release is
still unclear. Here, we investigated the effect of nonaggregated α-Syn
on SNARE-dependent liposome fusion using fluorescence methods. In
ensemble in vitro assays, α-Syn reduces lipid mixing mediated
by SNAREs. Furthermore, with the more advanced single-vesicle assay
that can distinguish vesicle docking from fusion, we found that α-Syn
specifically inhibits vesicle docking, without interfering with the
fusion. The inhibition in vesicle docking requires α-Syn binding
to acidic lipid containing membranes. Thus, these results imply the
existence of at least two mechanisms of inhibition of SNARE-dependent
membrane fusion: at high concentrations, nonaggregated α-Syn
inhibits docking by binding acidic lipids but not v-SNARE; on the
other hand, at much lower concentrations, large α-Syn oligomers
inhibit via a mechanism that requires v-SNARE interaction [Choi et al. 2013, 110 (10), 4087−409223431141].
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Affiliation(s)
- Ying Lai
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
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37
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Shah C, Hegde BG, Morén B, Behrmann E, Mielke T, Moenke G, Spahn CMT, Lundmark R, Daumke O, Langen R. Structural insights into membrane interaction and caveolar targeting of dynamin-like EHD2. Structure 2014; 22:409-420. [PMID: 24508342 DOI: 10.1016/j.str.2013.12.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/16/2013] [Accepted: 12/21/2013] [Indexed: 01/17/2023]
Abstract
The dynamin-related Eps15-homology domain-containing protein 2 (EHD2) is a membrane-remodeling ATPase that regulates the dynamics of caveolae. Here, we established an electron paramagnetic resonance (EPR) approach to characterize structural features of membrane-bound EHD2. We show that residues at the tip of the helical domain can insert into the membrane and may create membrane curvature by a wedging mechanism. Using EPR and X-ray crystallography, we found that the N terminus is folded into a hydrophobic pocket of the GTPase domain in solution and can be released into the membrane. Cryoelectron microscopy demonstrated that the N terminus is not essential for oligomerization of EHD2 into a membrane-anchored scaffold. Instead, we found a function of the N terminus in regulating targeting and stable association of EHD2 to caveolae. Our data uncover an unexpected, membrane-induced regulatory switch in EHD2 and demonstrate the versatility of EPR to study structure and function of dynamin superfamily proteins.
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Affiliation(s)
- Claudio Shah
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany.,Institute of Chemistry and Biochemistry, Free University Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Balachandra G Hegde
- Post Graduate Department of Physics, Rani Channamma University, Vidyasangama, Belagavi-591156, India
| | - Björn Morén
- Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Elmar Behrmann
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Thorsten Mielke
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany.,UltraStrukturNetzwerk, Max-Planck-Institute for Molecular Genetics, Ihnestraße 73, 14195 Berlin
| | - Gregor Moenke
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany
| | - Christian M T Spahn
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Richard Lundmark
- Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Oliver Daumke
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany.,Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
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38
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Varkey J, Mizuno N, Hegde BG, Cheng N, Steven AC, Langen R. α-Synuclein oligomers with broken helical conformation form lipoprotein nanoparticles. J Biol Chem 2013; 288:17620-30. [PMID: 23609437 DOI: 10.1074/jbc.m113.476697] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Synuclein (αS) is a membrane-binding protein with sequence similarity to apolipoproteins and other lipid-carrying proteins, which are capable of forming lipid-containing nanoparticles, sometimes referred to as "discs." Previously, it has been unclear whether αS also possesses this property. Using cryo-electron microscopy and light scattering, we found that αS can remodel phosphatidylglycerol vesicles into nanoparticles whose shape (ellipsoidal) and dimensions (in the 7-10-nm range) resemble those formed by apolipoproteins. The molar ratio of αS to lipid in nanoparticles is ∼1:20, and αS is oligomeric (including trimers and tetramers). Similar nanoparticles form when αS is added to vesicles of mitochondrial lipids. This observation suggests a mechanism for the previously reported disruption of mitochondrial membranes by αS. Circular dichroism and four-pulse double electron electron resonance experiments revealed that in nanoparticles αS assumes a broken helical conformation distinct from the extended helical conformation adopted when αS is bound to intact vesicles or membrane tubules. We also observed αS-dependent tubule and nanoparticle formation in the presence of oleic acid, implying that αS can interact with fatty acids and lipids in a similar manner. αS-related nanoparticles might play a role in lipid and fatty acid transport functions previously attributed to this protein.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, USA
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39
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Abstract
The islet in type 2 diabetes (T2DM) is characterized by a deficit in β-cells, increased β-cell apoptosis, and extracellular amyloid deposits derived from islet amyloid polypeptide (IAPP). In the absence of longitudinal studies, it is unknown if the low β-cell mass in T2DM precedes diabetes onset (is a risk factor for diabetes) or develops as a consequence of the disease process. Although insulin resistance is a risk factor for T2DM, most individuals who are insulin resistant do not develop diabetes. By inference, an increased β-cell workload results in T2DM in some but not all individuals. We propose that the extent of the β-cell mass that develops during childhood may underlie subsequent successful or failed adaptation to insulin resistance in later life. We propose that a low innate β-cell mass in the face of subsequent insulin resistance may expose β-cells to a burden of insulin and IAPP biosynthetic demand that exceeds the cellular capacity for protein folding and trafficking. If this threshold is crossed, intracellular toxic IAPP membrane permeant oligomers (cylindrins) may form, compromising β-cell function and inducing β-cell apoptosis.
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Affiliation(s)
- Safia Costes
- Division of Endocrinology, Larry L. Hillblom Islet Research Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA.
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40
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Cheng CY, Varkey J, Langen R, Han S. Hydration Dynamics as a Molecular Ruler for Refining Protein Structure at Lipid Membrane Interfaces. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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41
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Abstract
Fibrils formed by assembly of human islet amyloid polypeptide (hIAPP) are found in most patients with type II diabetes. Structurally, these fibrils are composed of multiple protofilaments and are characterized by extended beta sheets, variable helical twists, and different morphologies. We have previously derived models for the hIAPP protofilament using simulations constrained by data from EPR spectroscopy. In the current work, these models were used as a basis for generating idealized hIAPP protofilaments with symmetrical geometrical properties using a new algorithm, MFIBRIL. We show good agreement of the idealized protofilaments with experimental data for amino acid side chain orientations and geometrical features including the inter-β sheet distance and the protofilament radius. These idealized protofilaments can be used in MFIBRIL to generate fibril models that may be experimentally testable at the molecular level. MFIBRIL can also be used for building structures of any repetitive molecular assembly starting with a single building block obtained from any source.
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Affiliation(s)
- Yiyu Li
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089, USA
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42
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Lai CL, Jao CC, Lyman E, Gallop JL, Peter BJ, McMahon HT, Langen R, Voth GA. Membrane binding and self-association of the epsin N-terminal homology domain. J Mol Biol 2012; 423:800-17. [PMID: 22922484 PMCID: PMC3682188 DOI: 10.1016/j.jmb.2012.08.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 08/13/2012] [Accepted: 08/16/2012] [Indexed: 01/23/2023]
Abstract
Epsin possesses a conserved epsin N-terminal homology (ENTH) domain that acts as a phosphatidylinositol 4,5-bisphosphate‐lipid‐targeting and membrane‐curvature‐generating element. Upon binding phosphatidylinositol 4,5‐bisphosphate, the N-terminal helix (H0) of the ENTH domain becomes structured and aids in the aggregation of ENTH domains, which results in extensive membrane remodeling. In this article, atomistic and coarse-grained (CG) molecular dynamics (MD) simulations are used to investigate the structure and the stability of ENTH domain aggregates on lipid bilayers. EPR experiments are also reported for systems composed of different ENTH-bound membrane morphologies, including membrane vesicles as well as preformed membrane tubules. The EPR data are used to help develop a molecular model of ENTH domain aggregates on preformed lipid tubules that are then studied by CG MD simulation. The combined computational and experimental approach suggests that ENTH domains exist predominantly as monomers on vesiculated structures, while ENTH domains self-associate into dimeric structures and even higher‐order oligomers on the membrane tubes. The results emphasize that the arrangement of ENTH domain aggregates depends strongly on whether the local membrane curvature is isotropic or anisotropic. The molecular mechanism of ENTH‐domain-induced membrane vesiculation and tubulation and the implications of the epsin's role in clathrin-mediated endocytosis resulting from the interplay between ENTH domain membrane binding and ENTH domain self-association are also discussed.
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Affiliation(s)
- Chun-Liang Lai
- Department of Chemistry, Institute of Biophysical Dynamics, James Franck Institute, and Computation Institute, University of Chicago, 5735S Ellis Avenue, Chicago, IL 60637, USA
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43
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Woodham AW, Da Silva DM, Skeate JG, Raff AB, Ambroso MR, Brand HE, Isas JM, Langen R, Kast WM. The S100A10 subunit of the annexin A2 heterotetramer facilitates L2-mediated human papillomavirus infection. PLoS One 2012; 7:e43519. [PMID: 22927980 PMCID: PMC3425544 DOI: 10.1371/journal.pone.0043519] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 07/23/2012] [Indexed: 12/13/2022] Open
Abstract
Mucosotropic, high-risk human papillomaviruses (HPV) are sexually transmitted viruses that are causally associated with the development of cervical cancer. The most common high-risk genotype, HPV16, is an obligatory intracellular virus that must gain entry into host epithelial cells and deliver its double stranded DNA to the nucleus. HPV capsid proteins play a vital role in these steps. Despite the critical nature of these capsid protein-host cell interactions, the precise cellular components necessary for HPV16 infection of epithelial cells remains unknown. Several neutralizing epitopes have been identified for the HPV16 L2 minor capsid protein that can inhibit infection after initial attachment of the virus to the cell surface, which suggests an L2-specific secondary receptor or cofactor is required for infection, but so far no specific L2-receptor has been identified. Here, we demonstrate that the annexin A2 heterotetramer (A2t) contributes to HPV16 infection and co-immunoprecipitates with HPV16 particles on the surface of epithelial cells in an L2-dependent manner. Inhibiting A2t with an endogenous annexin A2 ligand, secretory leukocyte protease inhibitor (SLPI), or with an annexin A2 antibody significantly reduces HPV16 infection. With electron paramagnetic resonance, we demonstrate that a previously identified neutralizing epitope of L2 (aa 108-120) specifically interacts with the S100A10 subunit of A2t. Additionally, mutation of this L2 region significantly reduces binding to A2t and HPV16 pseudovirus infection. Furthermore, downregulation of A2t with shRNA significantly decreases capsid internalization and infection by HPV16. Taken together, these findings indicate that A2t contributes to HPV16 internalization and infection of epithelial cells and this interaction is dependent on the presence of the L2 minor capsid protein.
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Affiliation(s)
- Andrew W. Woodham
- Departments of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Diane M. Da Silva
- Department of Obstetrics & Gynecology, University of Southern California, Los Angeles, California, United States of America
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California, United States of America
| | - Joseph G. Skeate
- Departments of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Adam B. Raff
- Departments of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Mark R. Ambroso
- Department of Biochemistry & Molecular Biology, University of Southern California, Los Angeles, California, United States of America
| | - Heike E. Brand
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California, United States of America
| | - J. Mario Isas
- Department of Biochemistry & Molecular Biology, University of Southern California, Los Angeles, California, United States of America
| | - Ralf Langen
- Department of Biochemistry & Molecular Biology, University of Southern California, Los Angeles, California, United States of America
| | - W. Martin Kast
- Departments of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
- Department of Obstetrics & Gynecology, University of Southern California, Los Angeles, California, United States of America
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, California, United States of America
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44
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Abstract
Misfolding and aggregation of huntingtin is one of the hallmarks of Huntington disease, but the overall structure of these aggregates and the mechanisms by which huntingtin misfolds remain poorly understood. Here we used site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy to study the structural features of huntingtin exon 1 (HDx1) containing 46 glutamine residues in its polyglutamine (polyQ) region. Despite some residual structuring in the N terminus, we find that soluble HDx1 is highly dynamic. Upon aggregation, the polyQ domain becomes strongly immobilized indicating significant tertiary or quaternary packing interactions. Analysis of spin-spin interactions does not show the close contact between same residues that is characteristic of the parallel, in-register structure commonly found in amyloids. Nevertheless, the same residues are still within 20 Å of each other, suggesting that polyQ domains from different molecules come into proximity in the fibrils. The N terminus has previously been found to take up a helical structure in fibrils. We find that this domain not only becomes structured, but that it also engages in tertiary or quaternary packing interactions. The existence of spin-spin interactions in this region suggests that such contacts could be made between N-terminal domains from different molecules. In contrast, the C-terminal domain is dynamic, contains polyproline II structure, and lacks pronounced packing interactions. This region must be facing away from the core of the fibrils. Collectively, these data provide new constraints for building structural models of HDx1 fibrils.
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Affiliation(s)
- Charles W Bugg
- Biology Division, California Institute of Technology, Pasadena, California 91125, USA
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45
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Mizuno N, Varkey J, Kegulian NC, Hegde BG, Cheng N, Langen R, Steven AC. Remodeling of lipid vesicles into cylindrical micelles by α-synuclein in an extended α-helical conformation. J Biol Chem 2012; 287:29301-11. [PMID: 22767608 DOI: 10.1074/jbc.m112.365817] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Synuclein (αS) is a protein with multiple conformations and interactions. Natively unfolded in solution, αS accumulates as amyloid in neurological tissue in Parkinson disease and interacts with membranes under both physiological and pathological conditions. Here, we used cryoelectron microscopy in conjunction with electron paramagnetic resonance (EPR) and other techniques to characterize the ability of αS to remodel vesicles. At molar ratios of 1:5 to 1:40 for protein/lipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol), large spherical vesicles are converted into cylindrical micelles ~50 Å in diameter. Other lipids of the same charge (negative) exhibit generally similar behavior, although bilayer tubes of 150-500 Å in width are also produced, depending on the lipid acyl chains. At higher protein/lipid ratios, discoid particles, 70-100 Å across, are formed. EPR data show that, on cylindrical micelles, αS adopts an extended amphipathic α-helical conformation, with its long axis aligned with the tube axis. The observed geometrical relationship between αS and the micelle suggests that the wedging of its long α-helix into the outer leaflet of a membrane may cause curvature and an anisotropic partition of lipids, leading to tube formation.
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Affiliation(s)
- Naoko Mizuno
- Laboratory of Structural Biology, NIAMS, National Institutes of Health, Bethesda, MD 20892, USA.
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46
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Meier F, Abeywardana T, Dhall A, Marotta NP, Varkey J, Langen R, Chatterjee C, Pratt MR. Semisynthetic, site-specific ubiquitin modification of α-synuclein reveals differential effects on aggregation. J Am Chem Soc 2012; 134:5468-71. [PMID: 22404520 DOI: 10.1021/ja300094r] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process of neurodegeneration in Parkinson's Disease is intimately associated with the aggregation of the protein α-synuclein into toxic oligomers and fibrils. Interestingly, many of these protein aggregates are found to be post-translationally modified by ubiquitin at several different lysine residues. However, the inability to generate homogeneously ubiquitin modified α-synuclein at each site has prevented the understanding of the specific biochemical consequences. We have used protein semisynthesis to generate nine site-specifically ubiquitin modified α-synuclein derivatives and have demonstrated that different ubiquitination sites have differential effects on α-synuclein aggregation.
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Affiliation(s)
- Franziska Meier
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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Krishnamani V, Hegde BG, Langen R, Lanyi JK. Secondary and Tertiary Structure of Bacteriorhodopsin in the SDS Denatured State. Biochemistry 2012; 51:1051-60. [DOI: 10.1021/bi201769z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Venkatramanan Krishnamani
- Department
of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697, United States
| | - Balachandra G. Hegde
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
90033, United States
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
90033, United States
| | - Janos K. Lanyi
- Department
of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697, United States
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Hatmal MM, Li Y, Hegde BG, Hegde PB, Jao CC, Langen R, Haworth IS. Computer modeling of nitroxide spin labels on proteins. Biopolymers 2012; 97:35-44. [PMID: 21792846 PMCID: PMC3422567 DOI: 10.1002/bip.21699] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 06/24/2011] [Accepted: 06/25/2011] [Indexed: 01/26/2023]
Abstract
Electron paramagnetic resonance using site-directed spin labeling can be used as an approach for determination of protein structures that are difficult to solve by other methods. One important aspect of this approach is the measurement of interlabel distances using the double electron-electron resonance (DEER) method. Interpretation of experimental data could be facilitated by a computational approach to calculation of interlabel distances. We describe an algorithm, PRONOX, for rapid computation of interlabel distances based on calculation of spin label conformer distributions at any site of a protein. The program incorporates features of the label distribution established experimentally, including weighting of favorable conformers of the label. Distances calculated by PRONOX were compared with new DEER distances for amphiphysin and annexin B12 and with published data for FCHo2 (F-BAR), endophilin, and α-synuclein, a total of 44 interlabel distances. The program reproduced these distances accurately (r(2) = 0.94, slope = 0.98). For 9 of the 11 distances for amphiphysin, PRONOX reproduced the experimental data to within 2.5 Å. The speed and accuracy of PRONOX suggest that the algorithm can be used for fitting to DEER data for determination of protein tertiary structure.
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Affiliation(s)
- Ma’mon M. Hatmal
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern CA, Los Angeles, CA 90089, USA
- Department of Biochemistry, University of Southern California, Los Angeles, CA, 90033-9151, USA
| | - Yiyu Li
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern CA, Los Angeles, CA 90089, USA
| | - Balachandra G. Hegde
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
| | - Prabhavati B. Hegde
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
| | - Christine C. Jao
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
| | - Ralf Langen
- Department of Biochemistry, University of Southern California, Los Angeles, CA, 90033-9151, USA
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
| | - Ian S. Haworth
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern CA, Los Angeles, CA 90089, USA
- Department of Biochemistry, University of Southern California, Los Angeles, CA, 90033-9151, USA
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Abstract
Misfolding and amyloid fibril formation by human islet amyloid polypeptide (hIAPP) are thought to be important in the pathogenesis of type 2 diabetes, but the structures of the misfolded forms remain poorly understood. Here we developed an approach that combines site-directed spin labeling with continuous wave and pulsed EPR to investigate local secondary structure and to determine the relative orientation of the secondary structure elements with respect to each other. These data indicated that individual hIAPP molecules take up a hairpin fold within the fibril. This fold contains two β-strands that are much farther apart than expected from previous models. Atomistic structural models were obtained using computational refinement with EPR data as constraints. The resulting family of structures exhibited a left-handed helical twist, in agreement with the twisted morphology observed by electron microscopy. The fibril protofilaments contain stacked hIAPP monomers that form opposing β-sheets that twist around each other. The two β-strands of the monomer adopt out-of-plane positions and are staggered by about three peptide layers (∼15 Å). These results provide a mechanism for hIAPP fibril formation and could explain the remarkable stability of the fibrils. Thus, the structural model serves as a starting point for understanding and preventing hIAPP misfolding.
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Affiliation(s)
- Sahar Bedrood
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, USA
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Jensen MB, Bhatia VK, Jao CC, Rasmussen JE, Pedersen SL, Jensen KJ, Langen R, Stamou D. Membrane curvature sensing by amphipathic helices: a single liposome study using α-synuclein and annexin B12. J Biol Chem 2011; 286:42603-42614. [PMID: 21953452 DOI: 10.1074/jbc.m111.271130] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Preferential binding of proteins on curved membranes (membrane curvature sensing) is increasingly emerging as a general mechanism whereby cells may effect protein localization and trafficking. Here we use a novel single liposome fluorescence microscopy assay to examine a common sensing motif, the amphipathic helix (AH), and provide quantitative measures describing and distinguishing membrane binding and sensing behavior. By studying two AH-containing proteins, α-synuclein and annexin B12, as well as a range of AH peptide mutants, we reveal that both the hydrophobic and hydrophilic faces of the helix greatly influence binding and sensing. Although increased hydrophobic and electrostatic interactions with the membrane both lead to greater densities of bound protein, the former yields membrane curvature-sensitive binding, whereas the latter is not curvature-dependent. However, the relative contributions of both components determine the sensing of AHs. In contrast, charge density in the lipid membrane seems important primarily in attracting AHs to the membrane but does not significantly influence sensing. These observations were made possible by the ability of our assay to distinguish within our samples liposomes with and without bound protein as well as the density of bound protein. Our findings suggest that the description of membrane curvature-sensing requires consideration of several factors such as short and long range electrostatic interactions, hydrogen bonding, and the volume and structure of inserted hydrophobic residues.
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Affiliation(s)
- Martin Borch Jensen
- Bionanotechnology and Nanomedicine Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Nano-Science Center, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Vikram Kjøller Bhatia
- Bionanotechnology and Nanomedicine Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Nano-Science Center, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Christine C Jao
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033
| | - Jakob Ewald Rasmussen
- IGM-Bioorganic Chemistry, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Søren L Pedersen
- IGM-Bioorganic Chemistry, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Knud J Jensen
- IGM-Bioorganic Chemistry, Faculty of Life Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033
| | - Dimitrios Stamou
- Bionanotechnology and Nanomedicine Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Nano-Science Center, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
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