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Mencel ML, Bittner GD. Repair of traumatic lesions to the plasmalemma of neurons and other cells: Commonalities, conflicts, and controversies. Front Physiol 2023; 14:1114779. [PMID: 37008019 PMCID: PMC10050709 DOI: 10.3389/fphys.2023.1114779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 02/14/2023] [Indexed: 03/17/2023] Open
Abstract
Neuroscientists and Cell Biologists have known for many decades that eukaryotic cells, including neurons, are surrounded by a plasmalemma/axolemma consisting of a phospholipid bilayer that regulates trans-membrane diffusion of ions (including calcium) and other substances. Cells often incur plasmalemmal damage via traumatic injury and various diseases. If the damaged plasmalemma is not rapidly repaired within minutes, activation of apoptotic pathways by calcium influx often results in cell death. We review publications reporting what is less-well known (and not yet covered in neuroscience or cell biology textbooks): that calcium influx at the lesion sites ranging from small nm-sized holes to complete axonal transection activates parallel biochemical pathways that induce vesicles/membrane-bound structures to migrate and interact to restore original barrier properties and eventual reestablishment of the plasmalemma. We assess the reliability of, and problems with, various measures (e.g., membrane voltage, input resistance, current flow, tracer dyes, confocal microscopy, transmission and scanning electron microscopy) used individually and in combination to assess plasmalemmal sealing in various cell types (e.g., invertebrate giant axons, oocytes, hippocampal and other mammalian neurons). We identify controversies such as plug versus patch hypotheses that attempt to account for currently available data on the subcellular mechanisms of plasmalemmal repair/sealing. We describe current research gaps and potential future developments, such as much more extensive correlations of biochemical/biophysical measures with sub-cellular micromorphology. We compare and contrast naturally occurring sealing with recently-discovered artificially-induced plasmalemmal sealing by polyethylene glycol (PEG) that bypasses all natural pathways for membrane repair. We assess other recent developments such as adaptive membrane responses in neighboring cells following injury to an adjacent cell. Finally, we speculate how a better understanding of the mechanisms involved in natural and artificial plasmalemmal sealing is needed to develop better clinical treatments for muscular dystrophies, stroke and other ischemic conditions, and various cancers.
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Affiliation(s)
- Marshal L. Mencel
- Institute of Cell and Molecular Biology, University of Texas at Austin, Austin, TX, United States
| | - George D. Bittner
- Department of Neuroscience, University of Texas at Austin, Austin, TX, United States
- *Correspondence: George D. Bittner,
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Cabrera AP, Stoddard J, Santiago Tierno I, Matisioudis N, Agarwal M, Renner L, Palegar N, Neuringer M, McGill T, Ghosh K. Increased cell stiffness contributes to complement-mediated injury of choroidal endothelial cells in a monkey model of early age-related macular degeneration. J Pathol 2022; 257:314-326. [PMID: 35239183 DOI: 10.1002/path.5892] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 02/03/2022] [Accepted: 03/01/2022] [Indexed: 11/06/2022]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the aging population. Yet, no therapies exist for approximately 85% of all AMD patients who have the dry form that is marked by degeneration of the retinal pigmented epithelium (RPE) and underlying choroidal vasculature. As the choroidal vessels are crucial for RPE development and maintenance, understanding how they degenerate may lead to effective therapies for dry AMD. One likely causative factor for choroidal vascular loss is the cytolytic membrane attack complex (MAC) of the complement pathway that is abundant on choroidal vessels of humans with early dry AMD. To examine this possibility, we studied the effect of complement activation on choroidal endothelial cells (ECs) isolated from a rhesus monkey model of early AMD that, we report, exhibits MAC deposition and choriocapillaris endothelial loss similar to that seen in human early AMD. Treatment of choroidal ECs from AMD eyes with complement-competent normal human serum caused extensive actin cytoskeletal injury that was significantly less pronounced in choroidal ECs from young normal monkey eyes. We further show that ECs from AMD eyes are significantly stiffer than their younger counterparts and exhibit peripheral actin organization that is distinct from the longitudinal stress fibers in young ECs. Finally, these differences in complement susceptibility and mechanostructural properties were found to be regulated by the differential activity of the small GTPases Rac and Rho, because Rac inhibition in AMD cells led to simultaneous reduction in stiffness and complement susceptibility while Rho inhibition in young cells exacerbated complement injury. Thus, by identifying cell stiffness and cytoskeletal regulators Rac and Rho as important determinants of complement susceptibility, the current findings offer a new mechanistic insight into choroidal vascular loss in early AMD that warrants further investigation for assessment of translational potential. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Andrea P Cabrera
- Department of Bioengineering, University of California, Riverside, CA, USA
| | - Jonathan Stoddard
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR, USA
| | - Irene Santiago Tierno
- Department of Ophthalmology and Integrated Physiology Interdepartmental PhD Program, University of California, Los Angeles, CA, USA.,Molecular, Cellular, and Integrated Physiology Interdepartmental PhD Program, University of California, Los Angeles, CA, USA.,Doheny Eye Institute, Pasadena, CA, USA
| | | | - Mahesh Agarwal
- Department of Ophthalmology and Integrated Physiology Interdepartmental PhD Program, University of California, Los Angeles, CA, USA.,Doheny Eye Institute, Pasadena, CA, USA
| | - Lauren Renner
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR, USA
| | - Neha Palegar
- Department of Bioengineering, University of California, Riverside, CA, USA
| | - Martha Neuringer
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR, USA.,Casey Eye Institute, Oregon Health & Sciences University, Portland, OR, USA
| | - Trevor McGill
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR, USA.,Casey Eye Institute, Oregon Health & Sciences University, Portland, OR, USA
| | - Kaustabh Ghosh
- Department of Bioengineering, University of California, Riverside, CA, USA.,Department of Ophthalmology and Integrated Physiology Interdepartmental PhD Program, University of California, Los Angeles, CA, USA.,Molecular, Cellular, and Integrated Physiology Interdepartmental PhD Program, University of California, Los Angeles, CA, USA.,Doheny Eye Institute, Pasadena, CA, USA
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Dias C, Nita E, Faktor J, Tynan AC, Hernychova L, Vojtesek B, Nylandsted J, Hupp TR, Kunath T, Ball KL. CHIP-dependent regulation of the actin cytoskeleton is linked to neuronal cell membrane integrity. iScience 2021; 24:102878. [PMID: 34401662 PMCID: PMC8350547 DOI: 10.1016/j.isci.2021.102878] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/13/2021] [Accepted: 07/15/2021] [Indexed: 12/12/2022] Open
Abstract
CHIP is an E3-ubiquitin ligase that contributes to healthy aging and has been characterized as neuroprotective. To elucidate dominant CHIP-dependent changes in protein steady-state levels in a patient-derived human neuronal model, CHIP function was ablated using gene-editing and an unbiased proteomic analysis conducted to compare knock-out and wild-type isogenic induced pluripotent stem cell (iPSC)-derived cortical neurons. Rather than a broad effect on protein homeostasis, loss of CHIP function impacted on a focused cohort of proteins from actin cytoskeleton signaling and membrane integrity networks. In support of the proteomics, CHIP knockout cells had enhanced sensitivity to induced membrane damage. We conclude that the major readout of CHIP function in cortical neurons derived from iPSC of a patient with elevate α-synuclein, Parkinson's disease and dementia, is the modulation of substrates involved in maintaining cellular "health". Thus, regulation of the actin cytoskeletal and membrane integrity likely contributes to the neuroprotective function(s) of CHIP.
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Affiliation(s)
- Catarina Dias
- Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
- Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, The University of Edinburgh, Edinburgh EH16 4UU, UK
| | - Erisa Nita
- Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Jakub Faktor
- Research Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, 656 53 Brno, Czech Republic
- University of Gdansk, International Centre for Cancer Vaccine Science, 80-822 Gdansk, Poland
| | - Ailish C. Tynan
- Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Lenka Hernychova
- Research Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, 656 53 Brno, Czech Republic
| | - Borivoj Vojtesek
- Research Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, 656 53 Brno, Czech Republic
| | - Jesper Nylandsted
- Membrane Integrity Group, Danish Cancer Society Research Center, Strandboulevarden 49, 2100, Copenhagen, Denmark
| | - Ted R. Hupp
- Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
- University of Gdansk, International Centre for Cancer Vaccine Science, 80-822 Gdansk, Poland
| | - Tilo Kunath
- Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, The University of Edinburgh, Edinburgh EH16 4UU, UK
| | - Kathryn L. Ball
- Institute of Genetics and Cancer, University of Edinburgh, Edinburgh EH4 2XU, UK
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Splitting up to heal: mitochondrial shape regulates signaling for focal membrane repair. Biochem Soc Trans 2021; 48:1995-2002. [PMID: 32985660 DOI: 10.1042/bst20200120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 09/01/2020] [Accepted: 09/07/2020] [Indexed: 12/19/2022]
Abstract
Mitochondria are central to the health of eukaryotic cells. While commonly known for their bioenergetic role, mitochondria also function as signaling organelles that regulate cell stress responses capable of restoring homeostasis or leading the stressed cell to eventual death. Damage to the plasma membrane is a potentially fatal stressor incurred by all cells. Repairing plasma membrane damage requires cells to mount a rapid and localized response to injury. Accumulating evidence has identified a role for mitochondria as an important facilitator of this acute and localized repair response. However, as mitochondria are organized in a cell-wide, interconnected network, it is unclear how they collectively sense and respond to a focal injury. Here we will discuss how mitochondrial shape change is an integral part of this localized repair response. Mitochondrial fragmentation spatially restricts beneficial repair signaling, enabling a localized response to focal injury. Conservation of mitochondrial fragmentation in response to cell and tissue damage across species demonstrates that this is a universal pro-survival adaptation to injury and suggests that mitochondrial fragmentation may provide cells a mechanism to facilitate localized signaling in contexts beyond repairing plasma membrane injury.
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