Doncheva, D;
(2022)
ARMCX proteins regulate mitochondrial function in the Retinal Pigment Epithelium.
Doctoral thesis (Ph.D), UCL (University College London).
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D. Doncheva - PhD Thesis - ARMCX proteins regulate mitochondrial function in the Retinal Pigment Epithelium.pdf - Accepted Version Download (5MB) | Preview |
Abstract
Retinal Pigment Epithelium (RPE) functions, including energy absorption, photo-pigment recycling, and oxidative stress regulation, depend on a healthy mitochondrial network. Notably, RPE mitochondrial integrity declines during aging and even more so Age-related Macular Degeneration (AMD). Healthy mitochondria pervade the entirety of the cell as an organelle network undergoing constant dynamic renewal through fusion, fission and mitophagy. Armadillo repeat-containing genes located on the X chromosome (Armcx) form an Eutharian specific cluster of 6 genes which are implicated in mitochondrial motility in axons and, more generally, in mitophagy (as substrates of Parkin). Armcx6 is up-regulated in differentiated RPE whilst Armcx3 is down-regulated in AMD, collectively suggesting an important role in the homeostasis of RPE. This study specifically analysed the role of Armcx proteins in RPE cells. Armcx1, 2, 3 and 6 but not 4 or 5 are found as bona fide mitochondrial regulators and to be upregulated in RPE differentiation in vitro. Further analysis focused on Armcx1 and Armcx2 showed both proteins to affect mitochondrial network differently in RPE. Endogenous Armcx1 and Armcx2 were strongly associated with mitochondria in ARPE-19 cells and strongly expressed in the RPE layer of human retina. Armcx1 knockdown resulted in increased mitochondrial motility, whereas Armcx2 depletion led to decreased mitochondrial movements. Armcx overexpression resulted in aggregation and Page | 6 reduced mobility of mitochondria indicating disrupted dynamics. Armcx1 and Armcx2 knockdown resulted in fragmented mitochondria, however with different phenotypes, suggesting enhanced fission and/or mitophagy. Indeed, Armcx1 knockdown showed increased Parkin activation upon mitophagy induction, whereas Armcx2 resulted in no difference. In addition, Lamp2 expression was also affected differently, by Armcx1 depletion leading to upregulated Lamp2, in contrast to Armcx2 knockdown which decreased Lamp2 levels. Moreover, compensatory experiments using marsupial Armc10 revealed that Armcx1 and Armcx2 have acquired novel roles during their evolution in the Eutherian clade, probably to fulfil new functions essential to support the more complex Eutherian clade.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | ARMCX proteins regulate mitochondrial function in the Retinal Pigment Epithelium |
| Event: | University College London |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Ophthalmology |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10141711 |
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