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Abstract: Disrupted-In-Schizophrenia 1 (DISC1) was identified as a candidate gene for schizophrenia. DISC1 is disrupted by a balanced t(1;11)(q42.1;q14.3) translocation segregating with schizophrenia and related psychiatric illness in a large Scottish family. Here, we show that DISC1 interacts via its globular domain with the p40 subunit of the eukaryotic translation initiation factor 3. Furthermore, we found that overexpression of DISC1 in SH-SY5Y cells induces the assembly of eIF3- and TIA-1-positive stress granules (SGs), discrete cytoplasmic granules formed in response to environmental stresses. Our findings suggest that DISC1 may function as a translational regulator and may be involved in stress response. [Copyright &y& Elsevier]

While most asthma can be treated with steroids, about 10%, called severe asthma, is refractory to steroids. It has recently been shown that in a subgroup of severe asthma cases, neutrophils that infiltrate into the airways play an important role in inflammation. However, the mechanisms underlying this increased neutrophil infiltration are not well understood. Here, using a mouse model of steroid-resistant neutrophilic inflammation, we show that mice deficient for the RNA-binding protein Mex-3B have significantly less neutrophil infiltration in the airways than wild-type mice. We further demonstrate that Mex-3B post-transcriptionally upregulates CXCL2, a chemokine that induces neutrophil chemotaxis and migration. Moreover, we show that treatment with either anti-CXCL2 antibody or anti-Mex-3B antisense oligonucleotide suppresses neutrophilic allergic airway inflammation. These results suggest that Mex-3B-mediated induction of CXCL2 is crucial for steroid-resistant neutrophilic allergic airway inflammation. Our findings suggest new strategies for therapeutic intervention in steroid-resistant severe asthma. • Mex-3B is required for the development of neutrophilic airway inflammation. • Mex-3B upregulates CXCL2 expression post-transcriptionally. • Mex-3B-mediated induction of CXCL2 is important for neutrophilic airway inflammation. [ABSTRACT FROM AUTHOR]

LGR5 plays an important role in the self-renewal of stem cells and is used as a marker identifying self-renewing stem cells in small intestine and hair follicles. Moreover, LGR5 has been reported to be overexpressed in several cancers. SOX9 is a transcription factor that plays a key role in development, differentiation and lineage commitment in various tissues. It has also been reported that SOX9 is overexpressed in a variety of cancers and contributes to their malignant phenotype. Here we show that LGR5 is required for the tumorigenicity of glioblastoma cells. We further show that SOX9 is upregulated in glioblastoma cells and directly enhances the expression of LGR5. We also demonstrate that knockdown of SOX9 suppresses the proliferation and tumorigenicity of glioblastoma cells. These results suggest that SOX9-mediated transcriptional regulation of LGR5 is critical for the tumorigenicity of glioblastoma cells. We speculate that the SOX9-LGR5 pathway could be a potentially promising target for the therapy of glioblastoma. [ABSTRACT FROM AUTHOR]

Upon binding of a Wnt ligand to the frizzled (FZD)-low density lipoprotein receptor related protein 5/6 (LRP5/6) receptor complex, the β-catenin destruction complex, composed of Axin1, adenomatous polyposis coli (APC), glycogen synthase kinase 3 (GSK3) and casein kinase 1 (CK1), is immediately inactivated, which causes β-catenin stabilization. However, the molecular mechanism of signal transduction from the receptor complex to the β-catenin destruction complex is controversial. Here we show that Wnt3a treatment promotes the dissociation of the Axin1-APC complex in glioblastoma cells cultured in serum-free medium. Experiments with the GSK3 inhibitor BIO suggest that Axin1-APC dissociation was controlled by phosphorylation. Introduction of a phosphomimetic mutation into Thr160 of Axin1, located in the APC-binding region RGS, abrogated the interaction of Axin1 with APC. Consistent with these observations, the Axin1 phosphomimetic mutant lost the ability to reduce β-catenin stability and to repress β-catenin/TCF-dependent transcription. Taken together, our results suggest a novel mechanism of Wnt signaling through the dissociation of the β-catenin destruction complex by Axin1 Thr160 modification. [ABSTRACT FROM AUTHOR]

Highlights: [•] PCDH10 is required for the proliferation, survival and self-renewal of glioblastoma cells. [•] PCDH10 is required for glioblastoma cell migration and invasion. [•] PCDH10 is required for the tumorigenicity of glioblastoma cells. [•] PCDH10 may be a promising target for the therapy of glioblastoma. [Copyright &y& Elsevier]

Highlights: [•] The crystal structure of the human DLG1 GK domain was solved at 2.2Å resolution. [•] The peptide-binding site is bound to the C-terminal tail of another DLG1 molecule. [•] The main-chain direction of the tail is opposite to that of LGN bound to DLG1. [•] The side-chain interactions of DLG1 with the C-terminal tail resemble those with LGN. [ABSTRACT FROM AUTHOR]

Abstract: NDC1 is a transmembrane nucleoporin that is required for NPC assembly and nucleocytoplasmic transport. We show here that NDC1 directly interacts with the nucleoporin ALADIN, mutations of which are responsible for triple-A syndrome, and that this interaction is required for targeting of ALADIN to nuclear pore complexes (NPCs). Furthermore, we show that NDC1 is required for selective nuclear import. Our findings suggest that NDC1-mediated localization of ALADIN to NPCs is essential for selective nuclear protein import, and that abrogation of the interaction between ALADIN and NDC1 may be important for the development of triple-A syndrome. [Copyright &y& Elsevier]

Abstract: ICAT, inhibitor of β-catenin and T cell factor, or Ctnnbip1, is a negative regulator of the Wnt signaling pathway that interferes with the interaction between β-catenin and T cell factor. Some ICAT-deficient (ICAT−/−) embryos exhibit unilateral or bilateral renal agenesis. In this study, we investigated developmental processes in the ICAT−/− kidney. ICAT was highly expressed in both the ureteric bud (UB) and the surrounding metanephric mesenchymal (MM) cells in the metanephros of embryonic day E11.5–E13.5 wild-type (ICAT+/+) mouse. In the E12.5-ICAT−/− metanephros, UB branching was delayed, and a T-shaped, bifurcated UB was frequently seen; this was never seen in the E12.5-ICAT+/+ metanephros. More apoptotic MM cells were detected in the ICAT−/− metanephros than in the ICAT+/+ metanephros. These results suggest that the loss of ICAT gene function causes the arrest of UB branching and the apoptotic death of MM cells, resulting in renal agenesis. [Copyright &y& Elsevier]

Abstract: The APC-associated guanine nucleotide exchange factor (GEF) Asef regulates cell morphology and migration. Asef contains a pleckstrin homology (PH) domain in addition to Dbl homology (DH), APC-binding (ABR), and Src homology 3 (SH3) domains. Here we show that the PH domain of Asef binds to phosphatidylinositol 3,4,5-trisphophate [PtdIns(3,4,5)P3] and targets Asef to the cell–cell adhesion sites in MDCK II cells. Furthermore, we demonstrate that overexpression of Asef in MDCK II cells results in increases in the amounts of E-cadherin and the actin filaments at the sites of cell–cell contact. These results suggest that Asef is targeted via its PH domain to the cell–cell adhesion sites and is involved in the regulation of cell adhesion. [Copyright &y& Elsevier]

Abstract: The mammalian homolog of the Drosophila discs large tumor suppressor protein Dlg functions as a scaffolding protein that facilitates the transmission of diverse signals. In the present study, we attempted to identify the downstream target genes of Dlg, and found that Dlg up-regulates expression of the ELR+ CXC chemokine Scyb5, which has been implicated in the immune system. Our finding suggests that Scyb5 may play an important role in the tumor suppressor function of Dlg. [Copyright &y& Elsevier]

BAMBI is a transmembrane glycoprotein related to the transforming growth factor-β (TGF-β)-family type I receptors and functions as a negative regulator of TGF-β signaling during development. BAMBI is induced by BMP signaling through the evolutionary conserved BMP-responsive elements in its promoter. Furthermore, we have recently shown that Wnt/β-catenin signaling activates transcription of BAMBI and that BAMBI expression is aberrantly elevated in most colorectal carcinomas. Here, we show that BAMBI is also directly induced by TGF-β signaling, through the three tandem repeats of 13 bp sequences containing the SMAD-binding elements, which are distinct from the BMP-responsive element. Our findings suggest that BAMBI transcription is regulated by TGF-β signaling through direct binding of SMAD3 and SMAD4 to the BAMBI promoter. [Copyright &y& Elsevier]

Bone morphogenetic proteins (BMPs) play critical roles in cellular proliferation, differentiation, and programmed cell death in multiple tissues. An increasing body of recent evidence has suggested that classes of molecules collectively termed BMP antagonists play important roles for the local regulation of BMP actions by binding BMPs and neutralizing their activities. Uterine sensitization-associated gene-1 (USAG-1) was previously reported as a gene of unknown function, preferentially expressed in sensitized endometrium of the rat uterus. Here, we show that USAG-1 is abundantly expressed in the kidney and functions as a BMP antagonist. Recombinant USAG-1 binds directly to BMPs and antagonizes the BMP-mediated induction of alkaline phosphatase in C2C12 cells. USAG-1 also induces formation of secondary axis and/or hyperdorsalization when its mRNA is injected to Xenopus embryos. In the early stage of mouse embryogenesis, USAG-1 is expressed in the first and second branchial arches and in metanephros, while in later stages the expression is confined to renal tubules and ameloblasts of teeth. Postnatally, the expression is further restricted to distal tubules of kidney, in a pattern similar to the localization of BMP-7, which has been shown to be important in the development of kidney and preservation of adult renal functions under pathological stresses. Collectively, we suggest that USAG-1 is a BMP antagonist that interacts with BMP-7 in the developing and adult kidney. [Copyright &y& Elsevier]

Activation of Wnt signaling is an early event in colorectal tumorigenesis, while aberrant activation of non-receptor tyrosine kinase c-Src occurs during tumor progression. Here, we show that v-Src and receptor tyrosine kinase ErbB2 activate β-catenin–TCF-mediated transcription. The effect of v-Src was abrogated by a dominant-negative mutant of TCF and the tumor suppressor APC. Furthermore, the effect of v-Src was partially abrogated by a dominant-negative mutant of MAP kinase, suggesting that v-Src exerts its effect at least in part via the MAP kinase pathway. Our finding raises the possibility that aberrantly activated c-Src may enhance Wnt signaling and this may contribute to tumor progression. [Copyright &y& Elsevier]

While human T-cell leukemia virus type 1 (HTLV-1) is associated with the development of adult T-cell leukemia (ATL), HTLV-2 has not been reported to be associated with such malignant leukemias. HTLV-1 Tax1 oncoprotein transforms a rat fibroblast cell line (Rat-1) to form multiple large colonies in soft agar, and this activity is much greater than that of HTLV-2 Tax2. We have demonstrated here that the increased number of transformed colonies induced by Tax1 relative to Tax2 was mediated by a PDZ domain-binding motif (PBM) in Tax1, which is absent in Tax2. Tax1 PBM mediated the interaction of Tax1 with the discs large (Dlg) tumor suppressor containing PDZ domains, and the interaction correlated well with the transforming activities of Tax1 and the mutants. Through this interaction, Tax1 altered the subcellular localization of Dlg from the detergent-soluble to the detergent-insoluble fraction in a fibroblast cell line as well as in HTLV-1-infected T-cell lines. These results suggest that the interaction of Tax1 with PDZ domain protein(s) is critically involved in the transforming activity of Tax1, the activity of which may be a crucial factor in malignant transformation of HTLV-1-infected cells in vivo. [Copyright &y& Elsevier]

DNA unwinding factor (DUF) was discovered as an essential DNA replication factor in Xenopus egg extracts. DUF consists of an HMG protein and a homolog of Cdc68p/Spt16p, and has the capability of unwinding dsDNA. Here we have examined the interaction of DUF with chromatin. DUF was incorporated into chromatin assembled from sperm heads and from plasmid DNA in egg extracts. It was revealed that the chromatin assembled in egg extracts immunodepleted of DUF is less sensitive to micrococcal nuclease (NNase) digestion than that assembled in control extracts, indicating that chromatin containing DUF has more decompact structure than that without DUF. Also we found that DUF has a high affinity for core histones in vitro. We suggest that the function of DUF may be to make the chromatin structure accessible to replication factors. [Copyright &y& Elsevier]

The human homolog of the Drosophila discs large tumor suppressor protein (hDLG) functions as a scaffolding protein that facilitates the transmission of diverse downstream signals. Here we show that hDLG interacts through its PDZ domains with the carboxy-terminal S/TXV motif of the mitochondrial ribosomal protein S-34 (MRP-S34). Our results suggest that hDLG interacts with MRP-S34 prior to entry of MRP-S34 into the mitochondria and may be involved in the trafficking of MRP-S34. [Copyright &y& Elsevier]

DLG, the mammalian homolog of the Drosophila Discs Large suppressor protein, functions as a scaffolding protein that facilitates the transmission of diverse downstream signals. In the present study, we attempted to identify partner proteins for DLG, and found that DLG interacts through its PDZ domains with the ribosome receptor. The ribosome receptor is an integral endoplasmic reticulum protein that has been suggested to be involved in secretion. Our finding raises the possibility that DLG plays a role in the regulation of secretion by interacting with the ribosome receptor. [Copyright &y& Elsevier]

Underphosphorylated retinoblastoma (Rb) protein inhibits progression around the cell cycle by binding to transcription factors like E2F; subsequent hyperphosphorylation of Rb protein releases E2F from the complex so that it can then drive the cell into S phase. We immunolocalized Rb protein in human cells during the cell cycle. Rb protein translocated into nucleoli after DNA replication completed, and the nucleolar Rb was shown to be in the hyperphosphorylated form by immunoblotting. This form, but not its underphosphorylated counterpart, interacted with the nucleolar protein nucleophosmin/B23. The two formed a salt-resistant complex in vitro, and the two could be immunoprecipitated together from nucleolar extracts. These results suggest that hyperphosphorylated Rb protein is imported into nucleoli late in S or G2 phase with nucleophosmin/B23. Analysis of the nucleolar location of Rb protein using various deletion mutants tagged with the green fluorescent protein implicated pocket A of Rb protein as the region responsible for nucleolar targeting; this region also interacted with nucleophosmin/B23. Nucleolar translocation of Rb mutant was inhibited by introducing nucleophosmin/B23 antisense oligomer. These results suggest that nucleolar translocation of Rb protein is promoted by the binding with nucleophosmin/B23 via the pocket A region. [Copyright &y& Elsevier]