Medical Research Council (MRC) Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK.
Curr Biol. 2010 May 11;20(9):803-10. doi: 10.1016/j.cub.2010.03.056. Epub 2010 Apr 29.
The Drosophila genes fat (ft) and dachsous (ds) encode large atypical cadherins that collaborate to coordinately polarize cells in the plane of the epithelium (planar cell polarity) and to affect growth via the Warts/Hippo pathway. Ft and Ds form heterodimeric bridges that convey polarity information from cell to cell. four-jointed (fj) is a modulator of Ft/Ds activity that acts in a graded fashion in the abdomen, eye, and wing. Genetic evidence indicates that Fj acts via Ds and/or Ft, and here we demonstrate that Fj can act independently on Ds and on Ft. It has been reported that Fj has kinase activity and can phosphorylate a subset of cadherin domains of both Ft and Ds in vitro. We have used both cell and in vitro assays to measure binding between Ft and Ds. We find that phosphorylation of Ds reduces its affinity for Ft in both of these assays. By expressing forms of Ds that lack the defined phosphorylation sites or have phosphomimetic amino acids at these positions, we demonstrate that effects of Fj on wing size and planar polarity can be explained by Fj phosphorylating these sites.
果蝇基因 fat（ft）和 dachsous（ds）编码大型非典型钙黏蛋白，它们协同作用，协调上皮细胞的平面极性（平面细胞极性），并通过 Warts/Hippo 途径影响生长。Ft 和 Ds 形成异二聚体桥，将极性信息从一个细胞传递到另一个细胞。四联体（fj）是 Ft/Ds 活性的调节剂，在腹部、眼睛和翅膀中以分级的方式发挥作用。遗传证据表明 Fj 通过 Ds 和/或 Ft 发挥作用，在这里我们证明 Fj 可以独立于 Ds 和 Ft 发挥作用。据报道，Fj 具有激酶活性，可以体外磷酸化 Ft 和 Ds 的一部分钙黏蛋白结构域。我们使用细胞和体外测定法来测量 Ft 和 Ds 之间的结合。我们发现 Ds 的磷酸化降低了其在这两种测定法中与 Ft 的亲和力。通过表达缺乏定义的磷酸化位点或在这些位置具有磷酸模拟氨基酸的 Ds 形式，我们证明 Fj 通过磷酸化这些位点对翅膀大小和平坦极性的影响可以得到解释。
