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Wnt3a-Mediated Formation of Phosphatidylinositol 4,5-Bisphosphate Regulates LRP6 Phosphorylation

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Science  05 Sep 2008:
Vol. 321, Issue 5894, pp. 1350-1353
DOI: 10.1126/science.1160741

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Abstract

The canonical Wnt–β-catenin signaling pathway is initiated by inducing phosphorylation of one of the Wnt receptors, low-density lipoprotein receptor-related protein 6 (LRP6), at threonine residue 1479 (Thr1479) and serine residue 1490 (Ser1490). By screening a human kinase small interfering RNA library, we identified phosphatidylinositol 4-kinase type II α and phosphatidylinositol-4-phosphate 5-kinase type I (PIP5KI) as required for Wnt3a-induced LRP6 phosphorylation at Ser1490 in mammalian cells and confirmed that these kinases are important for Wnt signaling in Xenopus embryos. Wnt3a stimulates the formation of phosphatidylinositol 4,5-bisphosphates [PtdIns (4,5)P2] through frizzled and dishevelled, the latter of which directly interacted with and activated PIP5KI. In turn, PtdIns (4,5)P2 regulated phosphorylation of LRP6 at Thr1479 and Ser1490. Therefore, our study reveals a signaling mechanism for Wnt to regulate LRP6 phosphorylation.

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