Inhibition of WNT signaling by G protein-coupled receptor (GPCR) kinase 2 (GRK2).

Journal Article

Activation of Wnt signaling pathways causes release and stabilization of the transcription regulator beta-catenin from a destruction complex composed of axin and the adenomatous polyposis coli (APC) protein (canonical signaling pathway). Assembly of this complex is facilitated by a protein-protein interaction between APC and a regulator of G protein signaling (RGS) domain in axin. Because G protein-coupled receptor kinase 2 (GRK2) has a RGS domain that is closely related to the RGS domain in axin, we determined whether GRK2 regulated canonical signaling. We found that GRK2 inhibited Wnt1-induced activation of a reporter construct as well as reduced Wnt3a-dependent stabilization and nuclear translocation of beta-catenin. GRK2 enzymatic activity was required for this negative regulatory effect, and depletion of endogenous GRK2 using small interfering RNA enhanced canonical signaling. GRK2-dependent inhibition of canonical signaling is relevant to osteoblast (OB) biology because overexpression of GRK2 attenuated Wnt/beta-catenin signaling in calvarial OBs. Coimmunoprecipitation studies found that: 1) GRK2 bound APC; 2) The GRK2-APC interaction was promoted by GRK2 enzymatic activity; and 3) Deletion of the RGS domain in GRK2 prevented both the GRK2-APC interaction and GRK2-dependent inhibition of canonical signaling. These data suggest that: 1) GRK2 negatively regulates Wnt signaling; 2) GRK2-dependent inhibition of canonical signaling requires a protein-protein interaction between the RGS domain in GRK2 and APC; and 3) Enzymatic activity promotes the GRK2-APC interaction and is required for the negative regulatory effect on canonical signaling. We speculate that inhibiting GRK2 activity in bone-forming OBs might be a useful therapeutic strategy for increasing bone mass.

Full Text

Duke Authors

Cited Authors

  • Wang, L; Gesty-Palmer, D; Fields, TA; Spurney, RF

Published Date

  • September 2009

Published In

Volume / Issue

  • 23 / 9

Start / End Page

  • 1455 - 1465

PubMed ID

  • 19556343

Electronic International Standard Serial Number (EISSN)

  • 1944-9917

Digital Object Identifier (DOI)

  • 10.1210/me.2009-0084

Language

  • eng

Conference Location

  • United States