Fig. 5. TGF-ß activates discoidin domain receptor 1 via upregulation of Wnt5a in mice. (A) Immunoprecipitation of Ddr1 from protein lysate of DNIIR and wild-type mammary glands and western blotting for phosphotyrosine demonstrates diminished Ddr1 tyrosine phosphorylation in DNIIR glands compared with wild-type glands. (B) Primary epithelial cells cultured on type I collagen were treated with Wnt5a. Immunoprecipitation of Ddr1 and western blotting for phosphotyrosine shows an increase in Ddr1 phosphorylation within 30 minutes of Wnt5a treatment. (C) Western blots show TGF-ß1 is able to induce Ddr1 phosphorylation in primary epithelial cells after 30 hours, following induction of Wnt5a protein levels seen at 24 hours. (D) IP western blotting illustrates Wnt5a^-/- epithelial cells cultured on type I collagen were unable to undergo Ddr1 phosphorylation in response to TGF-ß1 treatment.