Casein Kinase 1 Delta in Wnt Signaling and Beyond

我们确定来自Ewing肿瘤的细胞在Wnt-3a的作用下形成神经突，并开始确定这种作用的机制。非典型PKCiota的敲除也阻断了wnt -3a依赖性神经突的生长。Wnt-3a刺激PKCi的磷酸化。Dvl2与PKCi共免疫沉淀，当Dvl2中的CK1磷酸化位点被丙氨酸残基取代时，这种相互作用不会发生。这些结果表明，CK1磷酸化Dvl2是Dvl2- pkci结合所必需的，这反过来可能是神经突生长所必需的。这项工作意义重大，不仅因为它提供了有关神经突形成机制的见解。在其他情况下，许多参与神经突生长的因素有助于细胞极性的形成，例如对细胞迁移至关重要的细胞延伸。抑制CK1d可阻断hTERT-RPE和mIMCD3细胞的原发性纤毛发生。小鼠胚胎成纤维细胞和CK1d缺失小鼠的视网膜细胞也表现出纤毛发生缺陷。对CK1d表达或催化活性的干扰破坏了参与纤毛运输的几种蛋白的核周围或纤毛分布，包括Rab11a、Rab8a、CEP290、PCM1和polycytin -2，以及AKAP450的高尔基分布。与其结合伙伴AKAP450相似，CK1d是高尔基体微管成核和维持高尔基体完整性所必需的。含有CK1d结合位点的AKAP450片段过表达抑制高尔基微管成核、IFT20的高尔基分布和纤毛发生。我们的研究结果表明，CK1d通过协调中心体和高尔基体附近或附近的多种因子的分布和可能的功能来促进纤毛运输，从而介导初级纤毛发生。原发纤毛缺陷是导致神经管缺陷、多囊肾病和倒立位等多种疾病的原因。异常的Wnt信号也可引起这些异常。因此，我们对CK1d和Dvl的研究可能为Wnt信号控制胚胎发育的途径及其失调在发病机制中的作用提供新的见解。

We established that cells from Ewing tumors form neurites in response to Wnt-3a and have begun to define the mechanisms that account for this effect. Knockdown of the atypical PKCiota also blocked Wnt-3a-dependent neurite outgrowth. Wnt-3a stimulated the phosphorylation of PKCi. Dvl2 co-immunoprecipitated with PKCi, and this interaction did not occur when CK1 phosphorylation sites in Dvl2 were replaced with alanine residues. These results suggested that Dvl2 phosphorylation by CK1 was required for Dvl2-PKCi binding, which in turn might be necessary for neurite outgrowth. This work is significant not only because it provides insights about mechanisms involved in the formation of neurites. Many of the factors that participate in neurite outgrowth contribute to cell polarity in other contexts such as the formation of cellular extensions critical for cell migration. Inhibition of CK1d blocked primary ciliogenesis in hTERT-RPE and mIMCD3 cells. Mouse embryonic fibroblasts and retinal cells from CK1d null mice also exhibited ciliogenesis defects. Interference with CK1d expression or catalytic activity disrupted the pericentrosomal or ciliary distribution of several proteins involved in ciliary transport, including Rab11a, Rab8a, CEP290, PCM1 and polycystin-2, as well as the Golgi distribution of AKAP450. Similar to its binding partner AKAP450, CK1d was required for microtubule nucleation at the Golgi and maintenance of Golgi integrity. Overexpression of an AKAP450 fragment containing the CK1d binding site inhibited Golgi-derived microtubule nucleation, Golgi distribution of IFT20 and ciliogenesis. Our results suggest that CK1d mediates primary ciliogenesis by coordinating the distribution and presumably function of multiple factors at or near the centrosome and Golgi to promote ciliary transport. Defective primary cilia are responsible for several disorders including neural tube defects, polycystic kidney disease and situs inversus. Aberrant Wnt signaling also can elicit these abnormalities. Thus, our studies of CK1d and Dvl may provide new insight about the ways in which Wnt signaling controls embryonic development and its dysregulation contributes to pathogenesis.