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. Author manuscript; available in PMC: 2007 Dec 3.
Published in final edited form as: Nature. 2005 Dec 8;438(7069):873–877. doi: 10.1038/nature04185

Figure 4. Membrane-associated GSK3 phosphorylates LRP6 and activates LRP6 and TCF/β-catenin signalling.

Figure 4

a. Membrane-associated GSK3α/β and CK1α/ε is independent of Wnt3a stimulation. 10% GSK3α/β and 20% CK1α/ε were detected in the membrane fraction, which was marked by the transferrin receptor (TfR) and a lack of α-tubulin. Wnt3a stabilized cytosolic β-catenin. b. mGSK3β, like GSK3β, promoted LRP6 PPPSP phosphorylation. mGSK3β (VSVG-tagged) and GSK3β (HA-tagged) were detected via the two antibodies. c, d. TCF/β–catenin reporter assays. mGSK3β activated, whereas GSK3β inhibited, LRP6 signalling (c). mGSK3β did not synergize with LRP6m5; the slight stimulation seen might be due to the endogenous LRP5/6 (d). e, f. mGSK3β synergized with LRP6 to induce axis duplication (e) and Xnr3 expression (f) in Xenopus embryos. RNA doses injected are per embryo. e. The number above each bar indicates embryos injected. f. RT-PCR assay. EF-1α: loading control; -RT: without reverse transcriptase; con: un-injected embryos.