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The Alzheimer's-related amyloid beta peptide is internalised by R28 neuroretinal cells and disrupts the microtubule associated protein 2 (MAP-2)

The Alzheimer's-related amyloid beta peptide is internalised by R28 neuroretinal cells and disrupts the microtubule associated protein 2 (MAP-2)
The Alzheimer's-related amyloid beta peptide is internalised by R28 neuroretinal cells and disrupts the microtubule associated protein 2 (MAP-2)
Age-related Macular Degeneration (AMD) is a common, irreversible blinding condition that leads to the loss of central vision. AMD has a complex aetiology with both genetic as well as environmental risks factors, and share many similarities with Alzheimer's disease. Recent findings have contributed significantly to unravelling its genetic architecture that is yet to be matched by molecular insights. Studies are made more challenging by observations that aged and AMD retinas accumulate the highly pathogenic Alzheimer's-related Amyloid beta (A?) group of peptides, for which there appears to be no clear genetic basis. Analyses of human donor and animal eyes have identified retinal A? aggregates in retinal ganglion cells (RGC), the inner nuclear layer, photoreceptors as well as the retinal pigment epithelium. A? is also a major drusen constituent; found correlated with elevated drusen-load and age, with a propensity to aggregate in retinas of advanced AMD. Despite this evidence, how such a potent driver of neurodegeneration might impair the neuroretina remains incompletely understood, and studies into this important aspect of retinopathy remains limited. In order to address this we exploited R28 rat retinal cells which due to its heterogeneous nature, offers diverse neuroretinal cell-types in which to study the molecular pathology of A?. R28 cells are also unaffected by problems associated with the commonly used RGC-5 immortalised cell-line, thus providing a well-established model in which to study dynamic A? effects at single-cell resolution. Our findings show that R28 cells express key neuronal markers calbindin, protein kinase C and the microtubule associated protein-2 (MAP-2) by confocal immunofluorescence which has not been shown before, but also calretinin which has not been reported previously. For the first time, we reveal that retinal neurons rapidly internalised A?1-42, the most cytotoxic and aggregate-prone amongst the A? family. Furthermore, exposure to physiological amounts of A?1-42 for 24 h correlated with impairment to neuronal MAP-2, a cytoskeletal protein which regulates microtubule dynamics in axons and dendrites. Disruption to MAP-2 was transient, and had recovered by 48 h, although internalised A? persisted as discrete puncta for as long as 72 h. To assess whether A? could realistically localise to living retinas to mediate such effects, we subretinally injected nanomolar levels of oligomeric A?1-42 into wildtype mice. Confocal microscopy revealed the presence of focal A? deposits in RGC, the inner nuclear and the outer plexiform layers 8 days later, recapitulating naturally-occurring patterns of A? aggregation in aged retinas. Our novel findings describe how retinal neurons internalise A? to transiently impair MAP-2 in a hitherto unreported manner. MAP-2 dysfunction is reported in AMD retinas, and is thought to be involved in remodelling and plasticity of post-mitotic neurons. Our insights suggest a molecular pathway by which this could occur in the senescent eye leading to complex diseases such as AMD.
0014-4835
110-121
Taylor-Walker, Georgia
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Lynn, Savannah A.
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Keeling, Eloise
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Munday, Rosie
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Johnston, David
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Page, Anton
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Scott, Jennifer A.
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Goverdhan, Srinivas
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Lotery, Andrew J.
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Ratnayaka, Janaka
002499b8-1a9f-45b6-9539-5ac145799dfd
Taylor-Walker, Georgia
3a1ef57d-3880-45c2-a41f-b6efe98e8902
Lynn, Savannah A.
de0c4ec2-8a3c-4b16-9e47-ea13abc32a3b
Keeling, Eloise
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Munday, Rosie
fbc25981-b45b-42da-9b86-86704cc1f8b1
Johnston, David
b41163c9-b9d2-425c-af99-2a357204014e
Page, Anton
3b346d6a-855c-4838-a609-5eb40257e7c6
Scott, Jennifer A.
a8d2adb9-5eb1-4efd-bc65-5dde57b12fc1
Goverdhan, Srinivas
9ae32d5a-5c82-48a4-962d-1ed8acc3991e
Lotery, Andrew J.
5ecc2d2d-d0b4-468f-ad2c-df7156f8e514
Ratnayaka, Janaka
002499b8-1a9f-45b6-9539-5ac145799dfd

Taylor-Walker, Georgia, Lynn, Savannah A. and Keeling, Eloise et al. (2016) The Alzheimer's-related amyloid beta peptide is internalised by R28 neuroretinal cells and disrupts the microtubule associated protein 2 (MAP-2). Experimental Eye Research, 153, 110-121. (doi:10.1016/j.exer.2016.10.013).

Record type: Article

Abstract

Age-related Macular Degeneration (AMD) is a common, irreversible blinding condition that leads to the loss of central vision. AMD has a complex aetiology with both genetic as well as environmental risks factors, and share many similarities with Alzheimer's disease. Recent findings have contributed significantly to unravelling its genetic architecture that is yet to be matched by molecular insights. Studies are made more challenging by observations that aged and AMD retinas accumulate the highly pathogenic Alzheimer's-related Amyloid beta (A?) group of peptides, for which there appears to be no clear genetic basis. Analyses of human donor and animal eyes have identified retinal A? aggregates in retinal ganglion cells (RGC), the inner nuclear layer, photoreceptors as well as the retinal pigment epithelium. A? is also a major drusen constituent; found correlated with elevated drusen-load and age, with a propensity to aggregate in retinas of advanced AMD. Despite this evidence, how such a potent driver of neurodegeneration might impair the neuroretina remains incompletely understood, and studies into this important aspect of retinopathy remains limited. In order to address this we exploited R28 rat retinal cells which due to its heterogeneous nature, offers diverse neuroretinal cell-types in which to study the molecular pathology of A?. R28 cells are also unaffected by problems associated with the commonly used RGC-5 immortalised cell-line, thus providing a well-established model in which to study dynamic A? effects at single-cell resolution. Our findings show that R28 cells express key neuronal markers calbindin, protein kinase C and the microtubule associated protein-2 (MAP-2) by confocal immunofluorescence which has not been shown before, but also calretinin which has not been reported previously. For the first time, we reveal that retinal neurons rapidly internalised A?1-42, the most cytotoxic and aggregate-prone amongst the A? family. Furthermore, exposure to physiological amounts of A?1-42 for 24 h correlated with impairment to neuronal MAP-2, a cytoskeletal protein which regulates microtubule dynamics in axons and dendrites. Disruption to MAP-2 was transient, and had recovered by 48 h, although internalised A? persisted as discrete puncta for as long as 72 h. To assess whether A? could realistically localise to living retinas to mediate such effects, we subretinally injected nanomolar levels of oligomeric A?1-42 into wildtype mice. Confocal microscopy revealed the presence of focal A? deposits in RGC, the inner nuclear and the outer plexiform layers 8 days later, recapitulating naturally-occurring patterns of A? aggregation in aged retinas. Our novel findings describe how retinal neurons internalise A? to transiently impair MAP-2 in a hitherto unreported manner. MAP-2 dysfunction is reported in AMD retinas, and is thought to be involved in remodelling and plasticity of post-mitotic neurons. Our insights suggest a molecular pathway by which this could occur in the senescent eye leading to complex diseases such as AMD.

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Accepted/In Press date: 11 October 2016
e-pub ahead of print date: 15 October 2016
Published date: December 2016
Organisations: Faculty of Medicine

Identifiers

Local EPrints ID: 402064
URI: http://eprints.soton.ac.uk/id/eprint/402064
ISSN: 0014-4835
PURE UUID: 0a91a46c-5b5a-426a-a97d-39d425c1621d
ORCID for Savannah A. Lynn: ORCID iD orcid.org/0000-0003-2513-3144
ORCID for David Johnston: ORCID iD orcid.org/0000-0001-6703-6014
ORCID for Andrew J. Lotery: ORCID iD orcid.org/0000-0001-5541-4305
ORCID for Janaka Ratnayaka: ORCID iD orcid.org/0000-0002-1027-6938

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Date deposited: 27 Oct 2016 10:25
Last modified: 18 Feb 2021 17:36

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