Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 2006 Jan 3;103(1):212-7. Epub 2005 Dec 21.

Gialpha and Gbeta subunits both define selectivity of G protein activation by alpha2-adrenergic receptors.

Author information

1
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. scott.gibson@utsouthwestern.edu

Abstract

Previous studies of the specificity of receptor interactions with G protein subunits in living cells have relied on measurements of second messengers or other downstream responses. We have examined the selectivity of interactions between alpha2-adrenergic receptors (alpha2R) and various combinations of Gialpha and Gbeta subunit isoforms by measuring changes in FRET between Gialpha-yellow fluorescent protein and cyan fluorescent protein-Gbeta chimeras in HeLa cells. All combinations of Gialpha1, -2, or -3 with Gbeta1, -2, or -4 were activated to some degree by endogenous alpha2Rs as judged by agonist-dependent decreases in FRET. The degree of G protein activation is determined by the combination of Gialpha and Gbeta subunits rather than by the identity of an individual subunit. RT-PCR analysis and small interfering RNA knockdown of alpha2R subtypes, followed by quantification of radiolabeled antagonist binding, demonstrated that HeLa cells express alpha2a- and alpha2b-adrenergic receptor isoforms in a 2:1 ratio. Increasing receptor number by overexpression of the alpha2aR subtype minimized the differences among coupling preferences for Gialpha and Gbeta isoforms. The molecular properties of each Gialpha, Gbeta, and alpha2-adrenergic receptor subtype influence signaling efficiency for the alpha2-adrenergic receptor-mediated signaling pathway.

PMID:
16371464
PMCID:
PMC1325004
DOI:
10.1073/pnas.0509763102
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center