The Regulator of G protein Signaling (RGS) proteins originally were identified as GTPase-activating proteins (GAPs) for heterotrimeric G protein ? subunits. However, many RGS proteins possess highly- conserved domains in addition to the signature RGS box, which empower a multifunctional character that underlies poorly understood but physiologically important interactions among components of heterotrimeric G protein signaling cascades as well as with other signaling pathways. The R7 subfamily of RGS proteins possess a distinctive G-?-like (GGL) domain that mediates specific and obligate heterodimer formation with the atypical G protein subunit, G?5, suggesting that these signaling proteins exhibit functions similar to conventional G?? dimers. Our recently refined crystal structure of G?5/RGS9 support this idea and provides a framework for testing hypotheses related to various binding interfaces of this dimer that likely subserve the organization and integration of higher-order, multifunctional G protein/GPCR/RGS complexes. Consequently, we propose to: 1) use crystallography and mutational analyses to define the complete functionality and G? specificity of RGS domains within full-length G??5/R7 dimers;2) extend our understanding of the functional and structural relationships between G??5/R7 dimers and their anchoring proteins, R9AP and R7BP;and 3) quantify the functional capacities of G??5/R7 dimers to interact with GDP- G? subunits and GPCRs using reconstituted systems of purified components. While it is clear that R7 proteins are required for proper signaling mediated by G protein-coupled receptors under a variety of physiological settings, the roles of these proteins in coordinating these signaling events are relatively poorly understood. The work proposed here is designed to place R7 proteins within a detailed structural and functional context with respect to G protein-coupled receptors and heterotrimeric G proteins. It is anticipated that these studies will then be used to guide treatment regimens in cases where coordinated signaling mediated by R7 proteins has failed.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM081881-03
Application #
7659551
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Dunsmore, Sarah
Project Start
2007-08-01
Project End
2011-07-31
Budget Start
2009-08-01
Budget End
2010-07-31
Support Year
3
Fiscal Year
2009
Total Cost
$277,400
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Pharmacology
Type
Schools of Medicine
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
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Heenan, Erin J; Vanhooke, Janeen L; Temple, Brenda R et al. (2009) Structure and function of Vps15 in the endosomal G protein signaling pathway. Biochemistry 48:6390-401
Cheever, Matthew L; Snyder, Jason T; Gershburg, Svetlana et al. (2008) Crystal structure of the multifunctional Gbeta5-RGS9 complex. Nat Struct Mol Biol 15:155-62