Wnt signaling is known for its roles in regulation of embryonic development and in tumorigenesis. The first Wnt gene was identified by virtue of its ability to induce mammary tumors in mice. Studies have now implicated Wnt signaling in many different types of tumors. The best characterized Wnt signaling pathway, the canonical Wnt signaling pathway, is initiated by the binding of canonical Wnts to their receptor complexes consisting of the LDL receptor-related protein (LRP) 5/6 and frizzled (Fz) proteins, which eventually leads to the stabilization of -catenin and activation of gene transcription. Despite remarkable advances in our understanding of Wnt signaling mechanisms, significant gaps still remain. These include the mechanism by which Wnt regulates LRP phosphorylation, an early intracellular event and the biochemical basis for the involvement of Wnt co-receptor Fz and downstream signaling molecule Dishevelled (Dvl) in the Wnt/2-catenin signaling pathway. By screening a siRNA library for human kinases, we identified a group of phosphatidylinositide (PtdIns) kinase siRNAs that could inhibit canonical Wnt signaling. We went on demonstrating that Wnt3a could induce the accumulation of PtdIns (4,5) P2 in mammalian cells, which depends on both Fz and Dvl. We also showed that PtdIns (4,5) P2 is required for Wnt3a-induced canonical signaling events. Moreover, we found that there is possible involvement of heterotrimeric G proteins in Wnt-regulated PtdIns (4,5) P2 formation. Furthermore, we have preliminary results to support the two possible mechanisms by which PtdIns (4,5)P2 may regulate LRP phosphorylation. Putting all of these together, we hypothesize that Wnt3a may, via Fz, Dvl and G, activate PtdIns kinases to stimulate the formation of PtdIns (4,5)P2, which in turn stimulates the phosphorylation of LRP5/6, an early Wnt signaling event. Specially, in this application we will: 1) Investigate the mechanisms by which Wnt3a induces the formation of PtdIns (4,5)P2. 2) Investigate the mechanisms by which PtdIns (4,5)P2 regulates LRP phosphorylation.

Public Health Relevance

Cell-cell communication is essential for normal functions of multi-cellular organisms including human. Problems in this process would lead to various pathological conditions including tumorigenesis. This research proposal is to understand how the Wnt protein, one of the key molecules in cell-cell communication, regulate cellular functions and how the defects in this mechanism would cause diseases.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA139395-04
Application #
8212562
Study Section
Intercellular Interactions (ICI)
Program Officer
Yassin, Rihab R,
Project Start
2009-04-01
Project End
2014-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
4
Fiscal Year
2012
Total Cost
$375,235
Indirect Cost
$148,507
Name
Yale University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Koraishy, Farrukh M; Silva, Cynthia; Mason, Sherene et al. (2014) Hepatocyte growth factor (Hgf) stimulates low density lipoprotein receptor-related protein (Lrp) 5/6 phosphorylation and promotes canonical Wnt signaling. J Biol Chem 289:14341-50
Kim, Ingyu; Pan, Weijun; Jones, Sara A et al. (2013) Clathrin and AP2 are required for PtdIns(4,5)P2-mediated formation of LRP6 signalosomes. J Cell Biol 200:419-28
Kang, Heeseog; Viollet, Benoit; Wu, Dianqing (2013) Genetic deletion of catalytic subunits of AMP-activated protein kinase increases osteoclasts and reduces bone mass in young adult mice. J Biol Chem 288:12187-96
Liu, Bei; Staron, Matthew; Hong, Feng et al. (2013) Essential roles of grp94 in gut homeostasis via chaperoning canonical Wnt pathway. Proc Natl Acad Sci U S A 110:6877-82
Li, Xiaofeng; Shan, Jufang; Chang, Woochul et al. (2012) Chemical and genetic evidence for the involvement of Wnt antagonist Dickkopf2 in regulation of glucose metabolism. Proc Natl Acad Sci U S A 109:11402-7
Shi, Tong; Bao, Ju; Wang, Nick X et al. (2012) Identification Of Small Molecule TRABID Deubiquitinase Inhibitors By Computation-Based Virtual Screen. BMC Chem Biol 12:4
Gan, Xiaoqing; Wang, Jiyong; Wang, Chen et al. (2012) PRR5L degradation promotes mTORC2-mediated PKC-δ phosphorylation and cell migration downstream of Gα12. Nat Cell Biol 14:686-96
Bao, Ju; Zheng, Jie J; Wu, Dianqing (2012) The structural basis of DKK-mediated inhibition of Wnt/LRP signaling. Sci Signal 5:pe22
Gan, Xiaoqing; Wang, Jiyong; Su, Bing et al. (2011) Evidence for direct activation of mTORC2 kinase activity by phosphatidylinositol 3,4,5-trisphosphate. J Biol Chem 286:10998-1002

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