TY - JOUR
T1 - Structural determinants of G-protein α subunit selectivity by regulator of G-protein signaling 2 (RGS2)
AU - Kimple, Adam J.
AU - Soundararajan, Meera
AU - Hutsell, Stephanie Q.
AU - Roos, Annette K.
AU - Urban, Daniel J.
AU - Setola, Vincent
AU - Temple, Brenda R.S.
AU - Roth, Bryan L.
AU - Knapp, Stefan
AU - Willard, Francis S.
AU - Siderovski, David P.
PY - 2009/7/17
Y1 - 2009/7/17
N2 - "Regulator of G-protein signaling" (RGS) proteins facilitate the termination of G protein-coupled receptor (GPCR) signaling via their ability to increase the intrinsic GTP hydrolysis rate of Gα subunits (known as GTPase-accelerating protein or "GAP" activity). RGS2 is unique in its in vitro potency and selectivity as a GAP for Gαq subunits. As many vasoconstrictive hormones signal via Gq heterotrimer-coupled receptors, it is perhaps not surprising that RGS2-deficient mice exhibit constitutive hypertension. However, to date the particular structural features within RGS2 determining its selectivity for Gαq over Gα i/o substrates have not been completely characterized. Here, we examine a trio of point mutations to RGS2 that elicits Gαi-directed binding and GAP activities without perturbing its association with Gαq. Using x-ray crystallography, we determined a model of the triple mutant RGS2 in complex with a transition state mimetic form of Gαi at 2.8-Å resolution. Structural comparison with unliganded, wild type RGS2 and of other RGS domain/Gα complexes highlighted the roles of these residues in wild type RGS2 that weaken Gαi subunit association. Moreover, these three amino acids are seen to be evolutionarily conserved among organisms with modern cardiovascular systems, suggesting that RGS2 arose from the R4-subfamily of RGS proteins to have specialized activity as a potent and selective Gαq GAP that modulates cardiovascular function.
AB - "Regulator of G-protein signaling" (RGS) proteins facilitate the termination of G protein-coupled receptor (GPCR) signaling via their ability to increase the intrinsic GTP hydrolysis rate of Gα subunits (known as GTPase-accelerating protein or "GAP" activity). RGS2 is unique in its in vitro potency and selectivity as a GAP for Gαq subunits. As many vasoconstrictive hormones signal via Gq heterotrimer-coupled receptors, it is perhaps not surprising that RGS2-deficient mice exhibit constitutive hypertension. However, to date the particular structural features within RGS2 determining its selectivity for Gαq over Gα i/o substrates have not been completely characterized. Here, we examine a trio of point mutations to RGS2 that elicits Gαi-directed binding and GAP activities without perturbing its association with Gαq. Using x-ray crystallography, we determined a model of the triple mutant RGS2 in complex with a transition state mimetic form of Gαi at 2.8-Å resolution. Structural comparison with unliganded, wild type RGS2 and of other RGS domain/Gα complexes highlighted the roles of these residues in wild type RGS2 that weaken Gαi subunit association. Moreover, these three amino acids are seen to be evolutionarily conserved among organisms with modern cardiovascular systems, suggesting that RGS2 arose from the R4-subfamily of RGS proteins to have specialized activity as a potent and selective Gαq GAP that modulates cardiovascular function.
UR - http://www.scopus.com/inward/record.url?scp=67749114694&partnerID=8YFLogxK
U2 - 10.1074/jbc.M109.024711
DO - 10.1074/jbc.M109.024711
M3 - Article
C2 - 19478087
AN - SCOPUS:67749114694
SN - 0021-9258
VL - 284
SP - 19402
EP - 19411
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 29
ER -