The regulation of cell movement by the ubiquitin system.

近轴原钙粘蛋白（PAPC）已被证明参与早期胚胎发生过程中原肠胚形成细胞的运动。 它首先在原肠胚早期的背边缘区表达，随后在爪蟾和斑马鱼中仅限于近轴中胚层。 使用非洲爪蟾胚胎，我们发现，PAPC的调节也在蛋白质水平和降解，并排除在轴向中胚层质膜的原肠胚晚期阶段。 PAPC的调节需要依赖于进化上保守的胞质结构域中的磷酸化的多聚泛素化。 我们还表明，PAPC的膜定位与低细胞运动性和磷酸化/泛素化的调节是必不可少的正常非洲爪蟾原肠胚细胞运动。 总之，我们的研究结果揭示了一种新的细胞粘附蛋白的调节机制，该系统在脊椎动物胚胎发生中起着至关重要的作用。

Paraxial protocadherin (PAPC) has been shown to be involved in gastrulation cell movements during early embryogenesis. It is first expressed in the dorsal marginal zone at the early gastrula stage and subsequently restricted to the paraxial mesoderm in Xenopus and zebrafish. Using Xenopus embryos, we found that PAPC is regulated also at the protein level and is degraded and excluded from the plasma membrane in the axial mesoderm by the late gastrula stage. Regulation of PAPC requires poly-ubiquitination that is dependent on phosphorylation in the evolutionarily conserved cytoplasmic domain. We also show that membrane localization of PAPC is associated with low cell motility and its regulation by phosphorylation/ubiquitination is essential for normal Xenopus gastrulation cell movements. Taken together, our findings unveiled a novel mechanism of regulation of a cell adhesion protein and that this system plays a crucial role in vertebrate embryogenesis.