Ctnnb1

This gene encodes not only an important cytoplasmic component of the classical cadherin adhesion complex that forms the adherens junction in epithelia and mediates cell-cell adhesion in many other tissues but also a key signaling molecule in the canonical Wnt signaling pathway that controls cell growth and differentiation during both normal development and tumorigenesis. The gene product contains a central armadillo-repeat containing domain through which it binds the cytoplasmic tail of classical cadherins; meanwhile, it also binds alpha-catenin, which further links the cadherin complex to the actin cytoskeleton either directly or indirectly. Beta-catenin is therefore necessary for the adhesive function of classical cadherins. Another key function of this protein is to mediate the canonical Wnt signaling pathway and regulate gene transcription. Without Wnt signal, cytoplasmic beta-catenin that is not associated with the cadherin complex is quickly phosphorylated at the N-terminal Ser/Thr residues by the so called degradation complex containing axin, adenomatous polyposis coli (APC), casein kinase I, and GSK3B, then ubiquitylated by beta-TrCP, and degraded by the proteasome. However, in the presence of Wnt signal, the degradation complex is disrupted and the stabilized cytoplasmic beta-catenin translocates into the nucleus, where it binds various transcription factors and, together with these factors, regulates the transcription of many downstream genes. Mutations of this gene have been linked with various types of tumors. Alternatively spliced variants have been found for this gene. [provided by RefSeq, Sep 2009]

本基因编码的蛋白质不仅构成经典钙粘蛋白粘附复合体的重要细胞质组分，该复合体在上皮细胞中形成粘附连接并介导许多其他组织的细胞间粘附，而且还作为经典Wnt信号通路中的关键信号分子，该通路在正常发育和肿瘤发生过程中调控细胞生长和分化。该基因产物含有一个中央的armadillo重复域，通过该域与经典钙粘蛋白的细胞质尾部结合；同时，它还与α-连环蛋白结合，进一步将钙粘蛋白复合物直接或间接地连接到细胞骨架。因此，β-连环蛋白对于经典钙粘蛋白的粘附功能是必需的。该蛋白质的另一项关键功能是介导经典Wnt信号通路并调节基因转录。在没有Wnt信号的情况下，未与钙粘蛋白复合体结合的细胞质β-连环蛋白会迅速在N端丝氨酸/苏氨酸残基处被所谓的降解复合物磷酸化，该降解复合物包含axin、腺瘤性息肉病蛋白（APC）、酪蛋白激酶I和GSK3B，然后被β-TrCP泛素化，并由蛋白酶体降解。然而，在Wnt信号存在的情况下，降解复合物被破坏，稳定的细胞质β-连环蛋白转移至细胞核，在那里它与多种转录因子结合，并与这些因子共同调节下游基因的转录。该基因的突变与多种肿瘤类型相关。此外，该基因还存在可变剪接变异体。[由RefSeq提供，2009年9月]