Casein Kinase 1 Delta in Wnt Signaling and Beyond

(A)我们确定了尤文瘤细胞对Wnt-3a的反应是形成神经突，并开始确定这种作用的机制。敲除非典型PKCiota也阻断Wnt-3a依赖性神经突生长。Wnt-3a刺激PKCi的磷酸化。Dvl 2与PKCi共免疫沉淀，当Dvl 2中的CK 1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，Dvl 2磷酸化CK 1所需的Dvl 2-PKCi结合，这反过来可能是必要的神经突生长。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。参与神经突生长的许多因素在其他情况下有助于细胞极性，例如形成对细胞迁移至关重要的细胞延伸。(B)抑制酪蛋白激酶1 δ（CK 1d），而不是CK 1 e，阻断了hTERT-RPE和mIMCD 3细胞中的初级纤毛发生。小鼠胚胎成纤维细胞（MEFs）和视网膜细胞Csnk 1d（CK 1d）null小鼠也表现出纤毛发生缺陷。CK 1d催化活性和中心体定位信号（CLS）是拯救CK 1d无效MEFs纤毛形成所必需的。此外，含有CLS的截短衍生物的表达从中心体置换全长CK 1d，并在对照MEFs中减少纤毛长度，表明中心体CK 1d在纤毛发生中具有作用。CK 1d抑制还改变了参与纤毛转运的几种蛋白质的核小体周围或纤毛分布，包括Rab 11 a、Rab 8a、CEP 290、PCM 1和多囊蛋白-2，以及其结合伴侣AKAP 450的高尔基体分布。正如AKAP 450所报道的，CK 1d是高尔基体微管成核和维持高尔基体完整性所必需的。过表达的AKAP 450片段含有CK 1d结合位点抑制高尔基体衍生的微管成核，高尔基体分布的IFFT 20和纤毛发生。我们的研究结果表明，CK 1d介导的初级纤毛发生的多种机制，一个涉及其中心体的功能，另一个依赖于其相互作用与AKAP 450在高尔基体，这是重要的维持高尔基体组织和极化贩运的多种因素，介导纤毛运输。(C)目前的研究集中在观察CK 1d表达或催化活性的抑制破坏DNA损伤修复和细胞周期调控。

(A) 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. (B) Inhibition of casein kinase 1 delta (CK1d), but not CK1e, blocked primary ciliogenesis in hTERT-RPE and mIMCD3 cells. Mouse embryonic fibroblasts (MEFs) and retinal cells from Csnk1d (CK1d) null mice also exhibited ciliogenesis defects. CK1d catalytic activity and centrosomal localization signal (CLS) were required to rescue cilia formation in CK1d null MEFs. Furthermore, expression of a truncated derivative containing the CLS displaced full-length CK1d from the centrosome and decreased ciliary length in control MEFs, suggesting that centrosomal CK1d has a role in ciliogenesis. CK1d inhibition also altered 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 its binding partner, AKAP450. As reported for 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 multiple mechanisms, one involving its centrosomal function and another dependent on its interaction with AKAP450 at the Golgi where it is important for maintaining Golgi organization and polarized trafficking of multiple factors that mediate ciliary transport. (C) Current research is focused on observations that inhibition of CK1d expression or catalytic activity disrupts DNA damage repair and cell cycle regulation.