R-spondin1 is a high affinity ligand for LRP6 and induces LRP6 phosphorylation and beta-catenin signaling |
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Authors: | Wei Qiou Yokota Chika Semenov Mikhail V Doble Brad Woodgett Jim He Xi |
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Institution: | Program of Neurobiology, Children's Hospital Boston, Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115, USA. |
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Abstract: | R-spondin proteins are newly identified secreted molecules that activate beta-catenin signaling. However, the mechanism of R-spondin action and its relationship with Wnt signaling remain unclear. Here we show that human R-spondin1 (hRspo1) is a high affinity ligand for the Wnt co-receptor LRP6 (K(d) = 1.2 nm). hRspo1 induces glycogen synthase kinase 3-dependent phosphorylation and activation of LRP6. DKK1, an LRP6 antagonist, inhibits hRspo1-induced LRP6 phosphorylation. We further demonstrate that hRspo1 synergizes with Frizzled5 in Xenopus axis induction assays and induces the phosphorylation of Dishevelled, a cytoplasmic component downstream of Frizzled function. Our study reveals interesting similarity and distinction between Wnt and R-spondin signaling. |
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