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Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology
Bester, D. 2025. Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7c3b449c-91e8-4c6f-a328-5ffd70c5cc3a
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| Language: | English |
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Stellenbosch University
2025
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| _version_ | 1867613930140991488 |
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| access_status_str | Open Access |
| author | Bester, Danelle |
| author2 | Huisamen, Barbara |
| author_browse | Bester, Danelle Huisamen, Barbara |
| author_facet | Huisamen, Barbara Bester, Danelle |
| author_sort | Bester, Danelle |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Bester, D. 2025. Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7c3b449c-91e8-4c6f-a328-5ffd70c5cc3a |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132105 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:57.787Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch University |
| publisherStr | Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132105 Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology Bester, Danelle Huisamen, Barbara Marais, Erna Blignaut, Marguerite Van Vuuren, Derick Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Protein kinases Endoplasmic reticulum Cardiovascular system -- Diseases -- Molecular aspects UCTD Bester, D. 2025. Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/7c3b449c-91e8-4c6f-a328-5ffd70c5cc3a Thesis (PhD)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Background: The endoplasmic reticulum (ER) is responsible for maintaining cellular protein homeostasis. Various stresses cause protein accumulation within the ER, leading to ER stress. This triggers a sophisticated unfolded protein response (UPR) to restore protein homeostasis, but can promote apoptosis in response to prolonged or severe stress. Obesity is associated with chronic ER stress, which is implicated in cardiovascular disease development. Thus, UPR modulators represent attractive therapeutic targets. However, the modulators of the UPR are poorly understood. Ataxia-telangiectasia mutated protein kinase (ATM) plays a well-defined cytoprotective role against genotoxic stress, oxidative stress, and proteotoxicity. Currently, a role for ATM within the UPR in response to ER stress has not been described, highlighting a novel area of research. This study aimed to investigate a novel role for ATM within the ER stress response in the context of obesity and cardiovascular disease. Methods: The role of ATM within the UPR was investigated in two in vitro models using the well-characterised HEK293 cell line as an explorative model, and the H9c2 cardiomyoblast cell line as a cardiac-like model. ER stress was pharmacologically induced (tunicamycin), with/without the chemical inhibition of ATM phosphorylation (KU-60019). Under these conditions, various UPR endpoints were assessed: UPR initiation proteins (qRT-PCR and Western blot), protein degradation pathways (qRT-PCR and Western blot), oxidative stress (DCF assay and Western blot), and apoptosis (MTT assay, crystal violet assay, qRT-PCR, and Western blot). The relationship between ATM and the UPR was investigated in the hearts of adult male and female ob/ob mice, a genetic model of obesity and cardiometabolic disease. ATM levels were determined (qRT-PCR and Western blot), together with various UPR endpoints: UPR initiation proteins (Western blot), autophagy (qRT-PCR and Western blot), oxidative stress (TBARS and Western blot), and apoptosis (qRT-PCR and Western blot). Results: In HEK293* and H9c2# cells, ATM was phosphorylated (activated) in response to tunicamycin-induced ER stress (p<0.001* and p<0.01#). ATM facilitated autophagy in response to tunicamycin, as ATM inhibition prior to tunicamycin treatment (KU-60019+tunicamycin) blocked cargo degradation, resulting in p62 accumulation (p<0.001* and p=0.058#). ATM protected against tunicamycin-induced ROS generation, as KU-60019+tunicamycin increased ROS levels (p<0.01* and p<0.05#). ATM protected against tunicamycin-induced apoptosis, as KU-60019+tunicamycin increased pro-apoptotic NOXA in HEK293 cells (p<0.05) and cell death in H9c2 cells (p<0.05). Phosphorylated ATM protein levels were downregulated in the hearts of obese ob/ob males (p<0.05) and females (p<0.01) compared to their respective C57BL/6J controls. Ob/ob females presented with cardiovascular disease onset, but not ob/ob males. In the hearts of ob/ob females, autophagy was defective as evidenced by decreased ATG7 expression (p<0.05), increased LC3 II/I ratio (p<0.05), and p62 accumulation (p<0.01). Furthermore, ob/ob females exhibited increased protein levels of the ER stress-mediated apoptotic protein CHOP (p<0.05). Conclusion: ATM plays an essential cytoprotective role within the UPR in response to ER stress in vitro. Furthermore, phosphorylated ATM is downregulated in the hearts of obese mice, which might be implicated in the shift towards chronic, pro-apoptotic UPR pathways in the context of obesity and cardiovascular disease. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-05-23T13:42:49Z 2025-05-23T13:42:49Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132105 en Stellenbosch University xxi, 231 pages : illustrations application/pdf Stellenbosch University |
| spellingShingle | Protein kinases Endoplasmic reticulum Cardiovascular system -- Diseases -- Molecular aspects UCTD Bester, Danelle Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title | Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title_full | Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title_fullStr | Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title_full_unstemmed | Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title_short | Investigating a potential role for ATM protein kinase in the ER stress response in cardiovascular pathology |
| title_sort | investigating a potential role for atm protein kinase in the er stress response in cardiovascular pathology |
| topic | Protein kinases Endoplasmic reticulum Cardiovascular system -- Diseases -- Molecular aspects UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132105 |
| work_keys_str_mv | AT besterdanelle investigatingapotentialroleforatmproteinkinaseintheerstressresponseincardiovascularpathology |