G protein-coupled receptor kinase 2 promotes high-level Hedgehog signaling by regulating the active state of Smo through kinase-dependent and kinase-independent mechanisms in Drosophila
- Yongbin Chen1,
- Shuang Li1,
- Chao Tong1,5,
- Yun Zhao1,6,
- Bing Wang1,
- Yajuan Liu2,3,
- Jianhang Jia2,3 and
- Jin Jiang1,4,7
- 1Department of Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA;
- 2Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40536, USA;
- 3Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA;
- 4Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
Abstract
G protein-coupled receptor kinase 2 (Gprk2/GRK2) plays a conserved role in modulating Hedgehog (Hh) pathway activity, but its mechanism of action remains unknown. Here we provide evidence that Gprk2 promotes high-level Hh signaling by regulating Smoothened (Smo) conformation through both kinase-dependent and kinase-independent mechanisms. Gprk2 promotes Smo activation by phosphorylating Smo C-terminal tail (C-tail) at Ser741/Thr742, which is facilitated by PKA and CK1 phosphorylation at adjacent Ser residues. In addition, Gprk2 forms a dimer/oligomer and binds Smo C-tail in a kinase activity-independent manner to stabilize the active Smo conformation, and promotes dimerization/oligomerization of Smo C-tail. Gprk2 expression is induced by Hh signaling, and Gprk2/Smo interaction is facilitated by PKA/CK1-mediated phosphorylation of Smo C-tail. Thus, Gprk2 forms a positive feedback loop and acts downstream from PKA and CK1 to facilitate high-level Hh signaling by promoting the active state of Smo through direct phosphorylation and molecular scaffolding.
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Footnotes
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↵7 Corresponding author.
E-MAIL jin.jiang{at}utsouthwestern.edu; FAX (214) 648-1960.
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Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.1948710.
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Supplemental material is available at http://www.genesdev.org.
- Received May 16, 2010.
- Accepted August 4, 2010.
- Copyright © 2010 by Cold Spring Harbor Laboratory Press