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Stroobants K, Kumita JR, Harris NJ, Chirgadze DY, Dobson CM, Booth PJ, Vendruscolo M. Amyloid-like Fibrils from an α-Helical Transmembrane Protein. Biochemistry 2017; 56:3225-3233. [PMID: 28493669 PMCID: PMC5489960 DOI: 10.1021/acs.biochem.7b00157] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The propensity to
misfold and self-assemble into stable aggregates
is increasingly being recognized as a common feature of protein molecules.
Our understanding of this phenomenon and of its links with human disease
has improved substantially over the past two decades. Studies thus
far, however, have been almost exclusively focused on cytosolic proteins,
resulting in a lack of detailed information about the misfolding and
aggregation of membrane proteins. As a consequence, although such
proteins make up approximately 30% of the human proteome and have
high propensities to aggregate, relatively little is known about the
biophysical nature of their assemblies. To shed light on this issue,
we have studied as a model system an archetypical representative of
the ubiquitous major facilitator superfamily, the Escherichia
coli lactose permease (LacY). By using a combination of established
indicators of cross-β structure and morphology, including the
amyloid diagnostic dye thioflavin-T, circular dichroism spectroscopy,
Fourier transform infrared spectroscopy, X-ray fiber diffraction,
and transmission electron microscopy, we show that LacY can form amyloid-like
fibrils under destabilizing conditions. These results indicate that
transmembrane α-helical proteins, similarly to cytosolic proteins,
have the ability to adopt this generic state.
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Affiliation(s)
- Karen Stroobants
- Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K
| | - Janet R Kumita
- Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K
| | - Nicola J Harris
- Department of Chemistry, King's College London , London SE1 1DB, U.K
| | - Dimitri Y Chirgadze
- Department of Biochemistry, University of Cambridge , Cambridge CB2 1GA, U.K
| | | | - Paula J Booth
- Department of Chemistry, King's College London , London SE1 1DB, U.K
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Hamilton RT, Bhattacharya A, Walsh ME, Shi Y, Wei R, Zhang Y, Rodriguez KA, Buffenstein R, Chaudhuri AR, Van Remmen H. Elevated protein carbonylation, and misfolding in sciatic nerve from db/db and Sod1(-/-) mice: plausible link between oxidative stress and demyelination. PLoS One 2013; 8:e65725. [PMID: 23750273 PMCID: PMC3672154 DOI: 10.1371/journal.pone.0065725] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/27/2013] [Indexed: 11/19/2022] Open
Abstract
Diabetic peripheral polyneuropathy is associated with decrements in motor/sensory neuron myelination, nerve conduction and muscle function; however, the mechanisms of reduced myelination in diabetes are poorly understood. Chronic elevation of oxidative stress may be one of the potential determinants for demyelination as lipids and proteins are important structural constituents of myelin and highly susceptible to oxidation. The goal of the current study was to determine whether there is a link between protein oxidation/misfolding and demyelination. We chose two distinct models to test our hypothesis: 1) the leptin receptor deficient mouse (dbdb) model of diabetic polyneuropathy and 2) superoxide dismutase 1 knockout (Sod1(-/-) ) mouse model of in vivo oxidative stress. Both experimental models displayed a significant decrement in nerve conduction, increase in tail distal motor latency as well as reduced myelin thickness and fiber/axon diameter. Further biochemical studies demonstrated that oxidative stress is likely to be a potential key player in the demyelination process as both models exhibited significant elevation in protein carbonylation and alterations in protein conformation. Since peripheral myelin protein 22 (PMP22) is a key component of myelin sheath and has been found mutated and aggregated in several peripheral neuropathies, we predicted that an increase in carbonylation and aggregation of PMP22 may be associated with demyelination in dbdb mice. Indeed, PMP22 was found to be carbonylated and aggregated in sciatic nerves of dbdb mice. Sequence-driven hydropathy plot analysis and in vitro oxidation-induced aggregation of purified PMP22 protein supported the premise for oxidation-dependent aggregation of PMP22 in dbdb mice. Collectively, these data strongly suggest for the first time that oxidation-mediated protein misfolding and aggregation of key myelin proteins may be linked to demyelination and reduced nerve conduction in peripheral neuropathies.
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Affiliation(s)
- Ryan T. Hamilton
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Arunabh Bhattacharya
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Michael E. Walsh
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
| | - Yun Shi
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Rochelle Wei
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Yiqiang Zhang
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Karl A. Rodriguez
- Department of Physiology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Rochelle Buffenstein
- Department of Physiology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
| | - Asish R. Chaudhuri
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
- Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, Texas, United States of America
- * E-mail: (ARC); (HV)
| | - Holly Van Remmen
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Department of Physiology, University of Texas Health Science Center, San Antonio, Texas, United States of America
- Sam and Ann Barshop Institute for Longevity and Aging Studies, San Antonio, Texas, United States of America
- Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, Texas, United States of America
- * E-mail: (ARC); (HV)
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Mobley CK, Myers JK, Hadziselimovic A, Ellis CD, Sanders CR. Purification and initiation of structural characterization of human peripheral myelin protein 22, an integral membrane protein linked to peripheral neuropathies. Biochemistry 2007; 46:11185-95. [PMID: 17824619 DOI: 10.1021/bi700855j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gene duplications, deletions, and point mutations in peripheral myelin protein 22 (PMP22) are linked to several inherited peripheral neuropathies. However, the structural and biochemical properties of this very hydrophobic putative tetraspan integral membrane protein have received little attention, in part because of difficulties in obtaining milligram quantities of wild type and disease-linked mutant forms of the protein. In this study a fusion protein was constructed consisting of a fragment of lambda repressor, a decahistidine tag, an intervening TEV protease cleavage site, a Strep tag, and the human PMP22 sequence. This fusion protein was expressed in Escherichia coli at a level of 10-20 mg/L of protein. Following TEV cleavage of the fusion partner, PMP22 was purified and its structural properties were examined in several different types of detergent micelles using cross-linking, near and far-UV circular dichroism, and nuclear magnetic resonance (NMR) spectroscopy. PMP22 is highly helical and, in certain detergents, shows evidence of stable tertiary structure. The protein exhibits a strong tendency to dimerize. The 1H-15N TROSY NMR spectrum is well dispersed and contains signals from all regions of the protein. It appears that detergent-solubilized PMP22 is amenable to detailed structural characterization via crystallography or NMR. This work sets the stage for more detailed studies of the structure, folding, and misfolding of wild type and disease-linked mutants in order to unravel the molecular defects underlying peripheral neuropathies.
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Affiliation(s)
- Charles K Mobley
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8725, USA
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Fortun J, Li J, Go J, Fenstermaker A, Fletcher BS, Notterpek L. Impaired proteasome activity and accumulation of ubiquitinated substrates in a hereditary neuropathy model. J Neurochem 2005; 92:1531-41. [PMID: 15748170 DOI: 10.1111/j.1471-4159.2004.02987.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Accumulation of misfolded proteins and alterations in the ubiquitin-proteasome pathway are associated with various neurodegenerative conditions of the CNS and PNS. Aggregates containing ubiquitin and peripheral myelin protein 22 (PMP22) have been observed in the Trembler J mouse model of Charcot-Marie-Tooth disease type 1A demyelinating neuropathy. In these nerves, the turnover rate of the newly synthesized PMP22 is reduced, suggesting proteasome impairment. Here we show evidence of proteasome impairment in Trembler J neuropathy samples compared with wild-type, as measured by reduced degradation of substrate reporters. Proteasome impairment correlates with increased levels of polyubiquitinated proteins, including PMP22, and the recruitment of E1, 20S and 11S to aggresomes formed either spontaneously due to the Trembler J mutation or upon proteasome inhibition. Furthermore, myelin basic protein, an endogenous Schwann cell proteasome substrate, associates with PMP22 aggregates in affected nerves. Together, our data show that in neuropathy nerves, reduced proteasome activity is coupled with the accumulation of ubiquitinated substrates, and the recruitment of proteasomal pathway constituents to aggregates. These results provide novel insights into the mechanism by which altered degradation of Schwann cell proteins may contribute to the pathogenesis of certain PMP22 neuropathies.
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Affiliation(s)
- Jenny Fortun
- Departments of Neuroscience and Pharmacology and Therapeutics, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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Liu N, Yamauchi J, Shooter EM. Recessive, but not dominant, mutations in peripheral myelin protein 22 gene show unique patterns of aggregation and intracellular trafficking. Neurobiol Dis 2004; 17:300-9. [PMID: 15474367 DOI: 10.1016/j.nbd.2004.07.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2004] [Revised: 06/22/2004] [Accepted: 07/09/2004] [Indexed: 11/26/2022] Open
Abstract
A characteristic feature of mouse models of the peripheral neuropathies caused by dominant mutations in peripheral myelin protein 22 (pmp22) is the appearance, in Schwann cells, of pmp22 aggregates. Using a set of dominant and recessive pmp22 mutations that cause human disease of varying degrees of severity, we compared their potential for aggregation and trafficking patterns with those of wild-type pmp22. The potential for aggregation was assessed by determining the size distribution of the various pmp22 mutant proteins under conditions where wild-type pmp22 showed little or no aggregation. All disease-causing dominant mutations showed significant aggregation and failed to traffic to the cell surface. Although the position of the dominant mutation in the pmp22 molecule determined both its potential for aggregation and how far it trafficked in the cell, there was no correlation between aggregation and the severity of the disease. On the other hand, recessive mutations were uniquely distinguished from dominant mutations by both the low potential for aggregation and their trafficking to the cell surface. In the course of these studies, it was also noted that the potential for aggregation and the trafficking of mutant pmp22s is influenced by the nature and/or location of the epitope tag.
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Affiliation(s)
- Ning Liu
- Department of Neurobiology, School of Medicine, Stanford University, Stanford, CA 94305, USA
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