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Publication Date
2023-5
First Advisor
Sharon Owino
Document Type
Honors Project
Degree Name
Bachelor of Arts
Department
Neuroscience
Keywords
amyloid beta, amyloid precurser protein, APP, Alzheimer's disease, AD, GPCR, G protein coupled receptor, GPR6, GPR12, GPR3, orphan GPCR
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disease that remains incurable. It is hypothesized that one of the main causes of AD is the oligomerization of Amyloid Beta (Aβ) peptides and their disposition into senile plaques, leading to synaptic dysfunction and neuronal degeneration. Aβ results from the cleavage of Amyloid precursor protein (APP) cleavage by β-secretase and γ-secretase. Treatment options through the elimination of APP or Aβ in the past did not yield long-term positive results, thus it is necessary to find molecular elements that can regulate this processing pathway. For example, G protein coupled receptor 3 (GPR3) was shown to be a positive regulator of APP processing leading to high levels of Aβ in both in vitro and in vivo models of AD. Therefore, in this study we aim to characterize the roles of GPR6 and GPR12 due to their high homology with GPR3. These three receptors were co-expressed in HEK293T cells with two APP isoforms, wild-type and mutant APP, which allows us to study these effects in sporadic and familial types of AD. APP levels were analyzed in the presence of each receptor using western blot analysis, with an emphasis on C-terminal fragments (CTFs) of app, primarily C-99 fragment, a direct precursor to Aβ. We also sought to understand the mechanisms through which these receptors elicit any observed effects, focusing mainly on G-protein signaling pathways. Overall, we were able to identify GPR6 as a possible downregulator of APP cleavage into C99, and thus could play a neuroprotective role against amyloidogenesis in both sporadic and familial forms of AD. On the other hand, GPR3 was a positive regulator of APP amyloidogenic processing leading to increased accumulation of C99, which is in line with previous research. However, GPR12 effects remain ambiguous and in between the two other receptors. Subsequently, we also observed a bidirectional effect between APP and G-protein signaling, suggesting a potential interaction between the receptors and APP. All together, this study set the stage for a new research direction focusing on GPR6 as a potential drug target in AD.
Rights
©2023 Sabra Mouhi. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.
Language
English
Recommended Citation
Mouhi, Sabra, "Characterization of Amyloid Precursor Protein Regulation by Orphan G Protein-Coupled Receptors 3, 6 and 12" (2023). Honors Project, Smith College, Northampton, MA.
https://scholarworks.smith.edu/theses/2566
Comments
47 pages: color illustrations. Includes bibliographical references (pages 42-47).