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Internalization of α-synuclein oligomers into SH-SY5Y cells. Biophys J 2021; 120:877-885. [PMID: 33515601 DOI: 10.1016/j.bpj.2020.12.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 12/09/2020] [Accepted: 12/30/2020] [Indexed: 11/20/2022] Open
Abstract
Aggregates of misfolded α-synuclein are a distinctive feature of Parkinson's disease. Small oligomers of α-synuclein are thought to be an important neurotoxic agent, and α-synuclein aggregates exhibit prion-like behavior, propagating misfolding between cells. α-Synuclein is internalized by both passive diffusion and active uptake mechanisms, but how uptake varies with the size of the oligomer is less clear. We explored how α-synuclein internalization into live SH-SY5Y cells varied with oligomer size by comparing the uptake of fluorescently labeled monomers to that of engineered tandem dimers and tetramers. We found that these α-synuclein constructs were internalized primarily through endocytosis. Oligomer size had little effect on their internalization pathway, whether they were added individually or together. Measurements of co-localization of the α-synuclein constructs with fluorescent markers for early endosomes and lysosomes showed that most of the α-synuclein entered endocytic compartments, in which they were probably degraded. Treatment of the cells with the Pitstop inhibitor suggested that most of the oligomers were internalized by the clathrin-mediated pathway.
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Gopal AA, Rappaz B, Rouger V, Martyn IB, Dahlberg PD, Meland RJ, Beamish IV, Kennedy TE, Wiseman PW. Netrin-1-Regulated Distribution of UNC5B and DCC in Live Cells Revealed by TICCS. Biophys J 2017; 110:623-634. [PMID: 26840727 DOI: 10.1016/j.bpj.2015.12.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/16/2015] [Accepted: 12/21/2015] [Indexed: 01/01/2023] Open
Abstract
Netrins are secreted proteins that direct cell migration and adhesion during development. Netrin-1 binds its receptors deleted in colorectal cancer (DCC) and the UNC5 homologs (UNC5A-D) to activate downstream signaling that ultimately directs cytoskeletal reorganization. To investigate how netrin-1 regulates the dynamic distribution of DCC and UNC5 homologs, we applied fluorescence confocal and total internal reflection fluorescence microscopy, and sliding window temporal image cross correlation spectroscopy, to measure time profiles of the plasma membrane distribution, aggregation state, and interaction fractions of fluorescently tagged netrin receptors expressed in HEK293T cells. Our measurements reveal changes in receptor aggregation that are consistent with netrin-1-induced recruitment of DCC-enhanced green fluorescent protein (EGFP) from intracellular vesicles to the plasma membrane. Netrin-1 also induced colocalization of coexpressed full-length DCC-EGFP with DCC-T-mCherry, a putative DCC dominant negative that replaces the DCC intracellular domain with mCherry, consistent with netrin-1-induced receptor oligomerization, but with no change in aggregation state with time, providing evidence that signaling via the DCC intracellular domain triggers DCC recruitment to the plasma membrane. UNC5B expressed alone was also recruited by netrin-1 to the plasma membrane. Coexpressed DCC and UNC5 homologs are proposed to form a heteromeric netrin-receptor complex to mediate a chemorepellent response. Application of temporal image cross correlation spectroscopy to image series of cells coexpressing UNC5B-mCherry and DCC-EGFP revealed a netrin-1-induced increase in colocalization, with both receptors recruited to the plasma membrane from preexisting clusters, consistent with vesicular recruitment and receptor heterooligomerization. Plasma membrane recruitment of DCC or UNC5B was blocked by application of the netrin-1 VI-V peptide, which fails to activate chemoattraction, or by pharmacological block of Src family kinase signaling, consistent with receptor recruitment requiring netrin-1-activated signaling. Our findings reveal a mechanism activated by netrin-1 that recruits DCC and UNC5B to the plasma membrane.
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Affiliation(s)
- Angelica A Gopal
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Benjamin Rappaz
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Vincent Rouger
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Iain B Martyn
- Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Peter D Dahlberg
- Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Rachel J Meland
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Ian V Beamish
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Timothy E Kennedy
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Paul W Wiseman
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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Lauterbach T, Manna M, Ruhnow M, Wisantoso Y, Wang Y, Matysik A, Oglęcka K, Mu Y, Geifman-Shochat S, Wohland T, Kraut R. Weak glycolipid binding of a microdomain-tracer peptide correlates with aggregation and slow diffusion on cell membranes. PLoS One 2012; 7:e51222. [PMID: 23251459 PMCID: PMC3520979 DOI: 10.1371/journal.pone.0051222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 10/30/2012] [Indexed: 11/18/2022] Open
Abstract
Organized assembly or aggregation of sphingolipid-binding ligands, such as certain toxins and pathogens, has been suggested to increase binding affinity of the ligand to the cell membrane and cause membrane reorganization or distortion. Here we show that the diffusion behavior of the fluorescently tagged sphingolipid-interacting peptide probe SBD (Sphingolipid Binding Domain) is altered by modifications in the construction of the peptide sequence that both result in a reduction in binding to ganglioside-containing supported lipid membranes, and at the same time increase aggregation on the cell plasma membrane, but that do not change relative amounts of secondary structural features. We tested the effects of modifying the overall charge and construction of the SBD probe on its binding and diffusion behavior, by Surface Plasmon Resonance (SPR; Biacore) analysis on lipid surfaces, and by Fluorescence Correlation Spectroscopy (FCS) on live cells, respectively. SBD binds preferentially to membranes containing the highly sialylated gangliosides GT1b and GD1a. However, simple charge interactions of the peptide with the negative ganglioside do not appear to be a critical determinant of binding. Rather, an aggregation-suppressing amino acid composition and linker between the fluorophore and the peptide are required for optimum binding of the SBD to ganglioside-containing supported lipid bilayer surfaces, as well as for interaction with the membrane. Interestingly, the strength of interactions with ganglioside-containing artificial membranes is mirrored in the diffusion behavior by FCS on cell membranes, with stronger binders displaying similar characteristic diffusion profiles. Our findings indicate that for aggregation-prone peptides, aggregation occurs upon contact with the cell membrane, and rather than giving a stronger interaction with the membrane, aggregation is accompanied by weaker binding and complex diffusion profiles indicative of heterogeneous diffusion behavior in the probe population.
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Affiliation(s)
- Tim Lauterbach
- School of Biological Sciences, Nanyang Technological University, Singapore
- Institut für Lebensmittel- und Bioverfahrenstechnik, Technische Universität Dresden, Dresden, Germany
| | - Manoj Manna
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Maria Ruhnow
- School of Biological Sciences, Nanyang Technological University, Singapore
- Institut für Lebensmittel- und Bioverfahrenstechnik, Technische Universität Dresden, Dresden, Germany
| | - Yudi Wisantoso
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Yaofeng Wang
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Artur Matysik
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Kamila Oglęcka
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore
| | | | - Thorsten Wohland
- Department of Chemistry, National University of Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore
| | - Rachel Kraut
- School of Biological Sciences, Nanyang Technological University, Singapore
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Rocheleau JV, Wiseman PW, Petersen NO. Isolation of bright aggregate fluctuations in a multipopulation image correlation spectroscopy system using intensity subtraction. Biophys J 2003; 84:4011-22. [PMID: 12770905 PMCID: PMC1302981 DOI: 10.1016/s0006-3495(03)75127-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Image correlation spectroscopy allows sensitive measurement of the spatial distribution and aggregation state of fluorescent membrane macro molecules. When studying a single population system (i.e., aggregates of similar brightness), an accurate measure can be made of the aggregate number per observation area, but this measurement becomes much more complex in a distributed population system (i.e., bright and faint aggregates). This article describes an alternate solution that involves extraction of the bright aggregate population information. This novel development for image correlation spectroscopy, termed intensity subtraction analysis, uses sequential uniform intensity subtraction from raw confocal images. Sequential intensity subtraction results in loss of faint aggregate fluctuations that are smaller in magnitude than fluctuations due to the brightest aggregates. The resulting image has correlatable fluctuations originating from only the brightest population, permitting quantification of this population's distribution and further cross-correlation measurements. The feasibility of this technique is demonstrated using fluorescent microsphere images and biological samples. The technique is further used to examine the spatial distribution of a plasma-membrane-labeled fluorescent synthetic ganglioside, and to cross-correlate this probe with various membrane markers. The evidence provided demonstrates that bright aggregates of the fluorescent ganglioside are associated with clathrin-coated pits, membrane microvilli, and detergent-resistant membranes.
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Affiliation(s)
- Jonathan V Rocheleau
- Department of Chemistry, Chemistry Building, University of Western Ontario, London, Ontario N6A 5B7, Canada
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Abstract
Disparate biological processes involve fusion of two membranes into one and fission of one membrane into two. To formulate the possible job description for the proteins that mediate remodeling of biological membranes, we analyze the energy price of disruption and bending of membrane lipid bilayers at the different stages of bilayer fusion. The phenomenology and the pathways of the well-characterized reactions of biological remodeling, such as fusion mediated by influenza hemagglutinin, are compared with those studied for protein-free bilayers. We briefly consider some proteins involved in fusion and fission, and the dependence of remodeling on the lipid composition of the membranes. The specific hypothetical mechanisms by which the proteins can lower the energy price of the bilayer rearrangement are discussed in light of the experimental data and the requirements imposed by the elastic properties of the bilayer.
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Affiliation(s)
- Leonid V Chernomordik
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, NICHD, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20892-1855, USA.
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