Arrestin proteins are master regulators of G protein coupled receptor (GPCR) signaling, and act in two ways. First, arrestins terminate the coupling of G proteins to cognate receptor by physically blocking the G protein coupling site. Second, arrestins can support G protein independent signaling. The best studied arrestin- mediated signaling pathways include the activation of mitogen activated protein (MAP) kinases. Recently we have determined the structure of activated arrestin-3, which shows the expected inter-domain twist. We also identified localized, previously unrecognized conformational changes in the effector binding regions of activated arrestin. Combining structural analysis with functional measurements, we propose a new paradigm for arrestin scaffolding of effectors via these sites, where the transition of arrestin into the active conformation can ?turn on? effector binding. Functionally analogous to `switch regions' of G proteins, these activation- dependent conformational changes in effector binding regions are 30-40 distal from the site of receptor (or non-receptor activator) binding and are distinct from activation-associated conformational changes previously described in the literature. We leverage this new finding with three aims that explore the connection between activation and effector binding in three aims.
In Aim 1, we combine in vitro structural and biophysical techniques (X-ray crystallography, multi-angle laser light scattering (MALLS), and affinity measurements, with double electron electron resonance (DEER) as an alternative approach) with single molecule and functional measurements in cells to investigate the role of oligomerization in stabilizing receptor-independent arrestin activation.
In Aim 2, we combine mutagenesis and functional analysis to reveal how arrestin-phosphate and arrestin- protein interactions at the activation sites of arrestin is allosterically transmitted to the effector binding sites, which are 30 ? 40 distal.
In Aim 3, we use new methods to stabilize the active form of arrestin-3 and use X-ray crystallography to identify the details of arrestin-effector interactions.

Public Health Relevance

Signaling initiated by G protein coupled receptors mediates the vast majority of information transfer in eukaryotic cells. Arrestins have long been known to act as terminators of G protein-mediated signaling, but there is growing appreciation for a second role of arrestins in directly scaffolding effectors. In proposed work, we leverage our recent discovery that arrestins use molecular switches to scaffold effector activation and investigate both how arrestins stabilize the active form and convert information about activation into a signal.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM120569-04
Application #
9736712
Study Section
Macromolecular Structure and Function B Study Section (MSFB)
Program Officer
Preusch, Peter
Project Start
2016-08-01
Project End
2020-06-30
Budget Start
2019-07-01
Budget End
2020-06-30
Support Year
4
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Pharmacology
Type
Schools of Medicine
DUNS #
965717143
City
Nashville
State
TN
Country
United States
Zip Code
37203
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