Todd, Nicholas
(2021)
The role of G protein-coupled receptor kinases in modulating γ-secretase activity and
amyloid-β generation.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Pathological changes in the Alzheimer’s disease (AD) brain begin up to 20 years prior to
the clinical onset of dementia, initially with the aggregation of amyloid-β (Aβ) peptides generated
via processive proteolytic cleavage of the amyloid precursor protein (APP) by β-secretase followed
by γ-secretase. The γ-secretase complex is a four-subunit aspartyl protease complex that consists
of a catalytic presenilin 1 or 2 (PS1 or PS2) subunit, nicastrin (NCT), presenilin enhancer 2
(PEN2), and anterior pharynx-defective 1 (APH1) A or B (APH1A or APH1B). The orphan G
protein-coupled receptor (GPCR) GPR3 is a regulator of γ-secretase activity and Aβ generation in
AD. GPR3-mediated γ-secretase activity requires GPR3 C-terminal phosphorylation and
recruitment of the multifunctional scaffolding protein β-arrestin 2 (βarr2). Canonical GPCR
phosphorylation is regulated via the family of kinases known as GPCR kinases (GRKs).
Interestingly, βarr2 has been shown to interact directly with the APH1A subunit of γ-secretase,
independent of a specific GPCR, to regulate γ-secretase activity. Furthermore, emerging evidence
suggests that GRKs regulate both Aβ and tau pathology in AD. Similar to GPCRs, APH1A
contains seven transmembrane domains and putative phosphorylation sites in intracellular loop 2
and the carboxy-terminus. Therefore, we hypothesized that the GRK family of kinases can directly
regulate γ-secretase activity via modulating non-canonical APH1A phosphorylation and
interaction with βarr2 and that specific GRKs can regulate GPR3-mediated Aβ via canonical
regulation of the GPCR GPR3. Here, we uncover a novel and constitutive role of the GRK family
v
of kinases in regulating APH1A phosphorylation and βarr2 interactions. We determine that distinct
GRK-mediated phosphorylation barcodes differentially regulate βarr2 binding and γ-secretase
cleavage of APP. Computational docking and molecular dynamic simulations reveal that βarr2
binds to APH1A in a similar fashion as a GPCR. Additionally, we discover that GRK2 kinase
activity specifically regulates GPR3-mediated Aβ generation. While the exact downstream
mechanisms of GPR3-βarr2 signaling that regulate Aβ generation are still undetermined, we
propose a model whereby both GPR3 trafficking and regulation of APH1A-βarr2 interaction are
involved. Together, this work suggests that drugs targeting the APH1A-βarr2 interaction and
GPR3 biased ligands may be therapeutically beneficial in AD.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
17 December 2021 |
| Date Type: |
Publication |
| Defense Date: |
28 October 2021 |
| Approval Date: |
17 December 2021 |
| Submission Date: |
30 November 2021 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
181 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Molecular Pharmacology |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
GRK
GPCR Kinase
G protein-coupled receptor kinase
Gamma secretase
Amyloid beta
APH1A |
| Date Deposited: |
17 Dec 2021 14:29 |
| Last Modified: |
17 Dec 2021 14:29 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/41986 |
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