Glycogen synthase kinase-3 (GSK-3) mediates epidermal growth factor, insulin and Wnt signals to various downstream events such as glycogen metabolism, gene expression, proliferation and differentiation. We have isolated here a GSK-3β-interacting protein from a rat brain cDNA library using a yeast twohybrid method. This protein consists of 832 amino acids and possesses Regulators of G protein Signaling (RGS) and dishevelled (Dsh) homologous domains in its N-and C-terminal regions, respectively. The predicted amino acid sequence of this GSK-3β-interacting protein shows 94% identity with mouse Axin, which recently has been identified as a negative regulator of the Wnt signaling pathway; therefore, we termed this protein rAxin (rat Axin). rAxin interacted directly with, and was phosphorylated by, GSK-3β. rAxin also interacted directly with the armadillo repeats of β-catenin. The binding site of rAxin for GSK-3β was distinct from the β-catenin-binding site, and these three proteins formed a ternary complex. Furthermore, rAxin promoted GSK-3β-dependent phosphorylation of β-catenin. These results suggest that rAxin negatively regulates the Wnt signaling pathway by interacting with GSK-3β and β-catenin and mediating the signal from GSK-3β to β-catenin.

Dectin-2 (gene symbol Clec4n) is a C-type lectin expressed by dendritic cells (DCs) and macrophages. However, its functional roles and signaling mechanisms remain to be elucidated. Here, we generated Clec4n(-/-) mice and showed that this molecule is important for host defense against Candida albicans (C. albicans). Clec4n(-/-) DCs had virtually no fungal alpha-mannan-induced cytokine production. Dectin-2 signaling induced cytokines through an FcRgamma chain and Syk-CARD9-NF-kappaB-dependent signaling pathway without involvement of MAP kinases. The yeast form of C. albicans induced interleukin-1beta (IL-1beta) and IL-23 secretion in a Dectin-2-dependent manner. In contrast, cytokine production induced by the hyphal form was only partially dependent on this lectin. Both yeast and hyphae induced Th17 cell differentiation, in which Dectin-2, but not Dectin-1, was mainly involved. Because IL-17A-deficient mice were highly susceptible to systemic candida infection, this study suggests that Dectin-2 is important in host defense against C. albicans by inducing Th17 cell differentiation.

The N-terminal region of Dvl-1 (a mammalian Dishevelled homolog) shares 37% identity with the C-terminal region of Axin, and this related region is named the DIX domain. The functions of the DIX domains of Dvl-1 and Axin were investigated. By yeast two-hybrid screening, the DIX domain of Dvl-1 was found to interact with Dvl-3, a second mammalian Dishevelled relative. The DIX domains of Dvl-1 and Dvl-3 directly bound one another. Furthermore, Dvl-1 formed a homo-oligomer. Axin also formed a homo-oligomer, and its DIX domain was necessary. The N-terminal region of Dvl-1, including its DIX domain, bound to Axin directly. Dvl-1 inhibited Axin-promoted glycogen synthase kinase 3beta-dependent phosphorylation of beta-catenin, and the DIX domain of Dvl-1 was required for this inhibitory activity. Expression of Dvl-1 in L cells induced the nuclear accumulation of beta-catenin, and deletion of the DIX domain abolished this activity. Although expression of Axin in SW480 cells caused the degradation of beta-catenin and reduced the cell growth rate, expression of an Axin mutant that lacks the DIX domain did not affect the level of beta-catenin or the growth rate. These results indicate that the DIX domains of Dvl-1 and Axin are important for protein-protein interactions and that they are necessary for the ability of Dvl-1 and Axin to regulate the stability of beta-catenin.

The regulators of G protein signaling (RGS) domain of Axin, a negative regulator of the Wnt signaling pathway, made a complex with full-length adenomatous polyposis coli (APC) in COS, 293, and L cells but not with truncated APC in SW480 or DLD-1 cells. The RGS domain directly interacted with the region containing the 20-amino acid repeats but not with that containing the 15-amino acid repeats of APC, although both regions are known to bind to ␤-catenin. In the region containing seven 20-amino acid repeats, the region containing the latter five repeats bound to the RGS domain of Axin. Axin and ␤-catenin simultaneously interacted with APC. Furthermore, Axin stimulated the degradation of ␤-catenin in COS cells. Taken together with our recent observations that Axin directly interacts with glycogen synthase kinase-3␤ (GSK-3␤) and ␤-catenin and that it promotes GSK-3␤-dependent phosphorylation of ␤-catenin, these results suggest that Axin, APC, GSK-3␤, and ␤-catenin make a tetrameric complex, resulting in the regulation of the stabilization of ␤-catenin.Axin, which is a product of the mouse Fused locus, has been identified as a negative regulator of the Wnt signaling pathway (1). Fused is a mutation that causes dominant skeletal and neurological defects and recessive lethal embryonic defects including neuroectodermal abnormalities (2-4). Because dorsal injection of wild type Axin in Xenopus embryos blocks axis formation and coinjection of Axin inhibits Wnt8-, Dsh-, and kinase-negative GSK-3␤ 1 -induced axis duplication (1), Axin could exert its effects on axis formation by inhibiting the Wnt signaling pathway. However, the molecular mechanism by which Axin regulates axis formation has not been shown. We have recently identified rat Axin (rAxin) as a GSK-3␤-interacting protein (5). rAxin is phosphorylated by GSK-3␤, directly binds to not only GSK-3␤ but also ␤-catenin, and promotes GSK-3␤-dependent phosphorylation of ␤-catenin (5). Because the phosphorylation of ␤-catenin by GSK-3␤ is essential for the down-regulation of ␤-catenin (6, 7), our results suggest that rAxin may induce the degradation of ␤-catenin. These actions of rAxin are consistent with the observation that Axin inhibits dorsal axis formation in Xenopus embryos, because the accumulation of ␤-catenin induces the axis duplication (8).It has been shown that besides the phosphorylation by GSK-3␤, the down-regulation of ␤-catenin requires APC, which is a tumor suppressor linked to FAP and to the initiation of sporadic human colorectal cancer (9). The middle portion of APC contains three successive 15-amino acid (aa) repeats followed by seven related but distinct 20-aa repeats. Both types of repeats are able to bind independently to ␤-catenin (10 -12). In FAP and colorectal cancers, most patients carry APC mutations that result in the expression of truncated proteins (9). Almost all mutant proteins lack the C-terminal half including most of the 20-aa repeats but retain the 15-aa repeats. Colorectal carcinoma cells with mutant APC contain large amounts of monom...

Axin forms a complex with glycogen synthase kinase-3␤ (GSK-3␤) and ␤-catenin and promotes GSK-3␤-dependent phosphorylation of ␤-catenin, thereby stimulating the degradation of ␤-catenin. Because GSK-3␤ also phosphorylates Axin in the complex, the physiological significance of the phosphorylation of Axin was examined. Treatment of COS cells with LiCl, a GSK-3␤ inhibitor, and okadaic acid, a protein phosphatase inhibitor, decreased and increased, respectively, the cellular protein level of Axin. Pulse-chase analyses showed that the phosphorylated form of Axin was more stable than the unphosphorylated form and that an Axin mutant, in which the possible phosphorylation sites for GSK-3␤ were mutated, exhibited a shorter half-life than wild type Axin. Dvl-1, which was genetically shown to function upstream of GSK-3␤, inhibited the phosphorylation of Axin by GSK-3␤ in vitro. Furthermore, Wnt-3a-containing conditioned medium down-regulated Axin and accumulated ␤-catenin in L cells and expression of Dvl-1 ⌬PDZ , in which the PDZ domain was deleted, suppressed this action of Wnt-3a. These results suggest that the phosphorylation of Axin is important for the regulation of its stability and that Wnt down-regulates Axin through Dvl.

Using a yeast two-hybrid method, we identified a novel protein which interacts with glycogen synthase kinase 3␤ (GSK-3␤). This protein had 44% amino acid identity with Axin, a negative regulator of the Wnt signaling pathway.We designated this protein Axil for Axin like. Like Axin, Axil ventralized Xenopus embryos and inhibited Xwnt8-induced Xenopus axis duplication. Axil was phosphorylated by GSK-3␤. Axil bound not only to GSK-3␤ but also to ␤-catenin, and the GSK-3␤-binding site of Axil was distinct from the ␤-catenin-binding site. Furthermore, Axil enhanced GSK-3␤-dependent phosphorylation of ␤-catenin. These results indicate that Axil negatively regulates the Wnt signaling pathway by mediating GSK-3␤-dependent phosphorylation of ␤-catenin, thereby inhibiting axis formation.Axin, which is a product of the mouse Fused locus, has been identified as a negative regulator of the Wnt signaling pathway (45). Fused is a mutation that causes dominant skeletal and neurological defects and recessive lethal embryonic defects including neuroectodermal abnormalities (36). Two spontaneous alleles of Fused, called Kinky (Fu Ki ) and Knobbly (Fu Kb ), and a transgenic insertional allele, Fu Tg1 , carry axis duplications and are lethal between 8 and 10 days postcoitus, suggesting that the Fused locus plays a role in the determination of the embryonic axis (9, 14, 33). The cDNA of this locus has been sequenced, and the Fused gene has been renamed Axin. Dorsal injection of wild-type Axin in Xenopus embryos blocks axis formation, and coinjection of Axin inhibits Wnt8-, dishevelled (Dsh)-, and kinase-negative glycogen synthase kinase 3␤ (GSK-3␤)-induced axis duplication (45). These results suggest that Axin exerts its effects on axis formation by inhibiting the signal transduction in the Wnt signaling pathway. However, the molecular mechanism by which Axin regulates axis formation is not known.Wnt and Wg signal many key developmental decisions, regulating anterior-posterior and dorsal-ventral patterns in both vertebrates and flies (22,30,31). In vertebrates, the Wnt signaling pathway consists of an intracellular cascade that includes frizzled, Dsh, GSK-3␤, and ␤-catenin (5). The Wnts are a family of secreted polypeptides, whose receptors are believed to be members of the frizzled family (3). It has been suggested that Dsh acts downstream of frizzled (22,30). GSK-3␤ is a constitutively active protein kinase and antagonizes downstream elements of the Wnt signaling pathway through changes in the ␤-catenin level (10). Wnt inactivates GSK-3␤ activity through Dsh, although by which mechanism is not known (6). In the presence of Wnt, there is a decrease in the phosphorylation of ␤-catenin and an increase in its stability, and ␤-catenin translocates to the nucleus (44). This translocation involves the association of ␤-catenin with the transcriptional enhancers of lymphocyte enhancer binding factor/T cell factor (LEF/ TCF) family (2, 24). ␤-Catenin has a consensus sequence of a phosphorylation site for GSK-3␤, and elimination of this possib...

Axin forms a complex with adenomatous polyposis coli gene product (APC), glycogen synthase kinase-3b (GSK3b), and b-catenin through di erent binding sites and downregulates b-catenin. GSK-3b-dependent phosphorylation of APC-(1211-2075) which has the Axin-binding site was facilitated by Axin, but that of APC-(959-1338) which lacks the Axin-binding site was not. Axin-(298-506) or Axin-(298-832), which has the GSK-3b-and bcatenin-but not APC-binding sites, did not enhance GSK-3b-dependent phosphorylation of either APC-(1211-2075) or APC-(959-1338). Furthermore, b-catenin stimulated the phosphorylation of APC-(959-1338) and APC-(1211-2075) by GSK-3b in the presence of Axin. Consistent with these in vitro observations, expression of b-catenin or Axin in COS cells promoted an SDS gel band shift of APC. These results indicate that APC complexed with Axin is e ectively phosphorylated by GSK-3b and that b-catenin may modulate this phosphorylation. In addition, the heterodimeric form of protein phosphatase 2A (PP2A) directly bound to Axin, and PP2A complexed with Axin dephosphorylated APC phosphorylated by GSK-3b. Taken together, these results suggest that GSK-3b-dependent phosphorylation of APC can be modulated by b-catenin and PP2A complexed with Axin. Oncogene (2000) 19, 537 ± 545.

PURPOSE It remains controversial whether primary tumor resection (PTR) before chemotherapy improves survival in patients with colorectal cancer (CRC) with asymptomatic primary tumor and synchronous unresectable metastases. PATIENTS AND METHODS This randomized phase III study investigated the superiority of PTR followed by chemotherapy versus chemotherapy alone in relation to overall survival (OS) in patients with unresectable stage IV asymptomatic CRC and three or fewer unresectable metastatic diseases confined to the liver, lungs, distant lymph nodes, or peritoneum. Chemotherapy regimens of either mFOLFOX6 plus bevacizumab or CapeOX plus bevacizumab were decided before study entry. The primary end point was OS, which was analyzed by intention-to-treat. RESULTS Between June 2012 and September 2019, a total of 165 patients were randomly assigned to either chemotherapy alone (84 patients) or PTR plus chemotherapy (81 patients). When the first interim analysis was performed in September 2019 with 50% (114/227) of the expected events observed among 160 patients at the data cutoff date of June 5, 2019, the Data and Safety Monitoring Committee recommended early termination of the trial because of futility. With a median follow-up of 22.0 months, median OS was 25.9 months (95% CI, 19.9 to 31.5) in the PTR plus chemotherapy arm and 26.7 (95% CI, 21.9 to 32.5) in the chemotherapy-alone arm (hazard ratio, 1.10; 95% CI, 0.76 to 1.59; one-sided P = .69). Three postoperative deaths occurred in the PTR plus chemotherapy arm. CONCLUSION Given that PTR followed by chemotherapy showed no survival benefit over chemotherapy alone, PTR should no longer be considered a standard of care for patients with CRC with asymptomatic primary tumors and synchronous unresectable metastases.