THE EVALUATION OF EXPRESSION OF EIF3 SUBUNITS AND RIBOSOMAL PROTEINS IN MICROGLIA DURING AGING IN WILD TYPE AND APP/PS1 MICE MODEL AND THE ASSESMENT OF EFFECT OF TOMIVOSERTIB ON EIF4E PHOSPHORYLATION

Date

2023-7-26

Author

Missaghimamaghani, Olka

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Microglia, the resident immune cells of the central nervous system, play a crucial role in maintaining brain homeostasis and responding to pathological changes. However, the aging process can significantly impact microglial function, leading to neurodegenerative diseases like Alzheimer's disease (AD). One aspect of microglial dysfunction during aging involves changes in gene expression, causing abnormal activation or suppression of specific genes. This abnormal gene expression contributes to the pro-inflammatory state observed in aging microglia and AD. In AD, microglia are responsible for clearing amyloid-beta (Aβ) plaques, a key pathology in the disease. Aging-related alterations impair the microglial ability to effectively remove Aβ plaques, leading to their accumulation and subsequent neuroinflammation. Aberrant gene expression in aging microglia affects phagocytic activity, inflammatory response, and release of neurotoxic factors, exacerbating AD progression. Studies have shown that certain Eukaryotic Translation Initiation Factor 3 (EIF3) subunits and ribosomal proteins (RP) involved in translation initiation are upregulated in aging microglia at mRNA level. However, the upregulation of these proteins should be examined at the protein level as well due to the post-transcription and translational regulatory processes. Therefore, the levels of these proteins were examined in wild type and APP/PS1 mouse models during aging. The results revealed an increase in different subunits of translation initiation factor 3 specifically EIF3H, EIF3E, EIF3K, and p-EIF4E in microglia during aging and with progression of AD. While RPL7, RPL7A, and RPS25 exhibited a different pattern. Although the results demonstrate upregulation of these proteins in an age-related manner, in APP mice, these proteins showed downregulation compared to wild type mice of the same age. These distinct regulation patterns suggested a crucial role of these proteins in aging and AD. Furthermore, to enhance our comprehension of the functions of EIF3H and EIF3E, we undertook a nucleofection-based strategy to overexpress these proteins within microglial cells. However, the nucleofection attempts were unsuccessful as often reported in the literature for BV-2 cell line. Understanding the significance of aberrant gene expression in aging microglia and its association with AD is crucial for targeted therapeutic strategies. Modulating gene expression and restoring normal microglial function may hold promise in reducing neuroinflammation, promoting Aβ clearance, and potentially slowing down AD progression. EIF4E, also known as eukaryotic translation initiation factor 4E, plays a crucial role in regulating protein synthesis. One of the key mechanisms governing the activity of EIF4E is its phosphorylation which is vital for modulating EIF4E's function and fine-tuning translation initiation. Phosphorylation of EIF4E is tightly regulated by various signaling pathways and is essential for controlling gene expression in response to different cellular stimuli. It acts as a molecular switch, influencing the assembly of the translation initiation complex and determining the efficiency of protein synthesis. Understanding the importance of EIF4E phosphorylation opens avenues for potential therapeutic interventions targeting this key protein and therefore regulating the rate of protein synthesis in this regard. As part of this exploration, we investigated the effect of Tomivosertib, an inhibitor of EIF4E phosphorylation, which controls translation rates. The results demonstrated that Tomivosertib effectively inhibits EIF4E phosphorylation by suppressing MNK1/2 in microglia, thereby decreasing translation rates and alleviating neuroinflammation.

Subject Keywords

Alzheimer's disease, Amyloid-beta, Eukaryotic Translation Initiation Factor, Ribosomal Protein

URI

https://hdl.handle.net/11511/105243

Collections

Graduate School of Natural and Applied Sciences, Thesis