Identification and characterization of endonuclein binding proteins: evidence of modulatory effects on signal transduction and chaperone activity

PWP1 Promotes the Malignant Phenotypes of Lung Cancer Cells by Interacting with DVL2 and Merlin

Purpose

The significance of periodic tryptophan protein 1 (PWP1) expression in human cancer and its molecular mechanism of action have not been reported so far.

Materials and Methods

Immunohistochemistry was performed to analyze the expression of PWP1 in non-small cell lung cancer (NSCLC) tissues and statistical analysis was applied to analyze the relationship between PWP1 expression and the clinicopathological factors. The effects of PWP1 on NSCLC proliferation and invasion were determined by colony formation, transwell and MTT assays. Western blot analysis (WB), dual-luciferase reporter gene assays and immunofluorescence staining were performed to demonstrate whether PWP1 stimulates Wnt pathway and inhibits Hippo pathway. Co-immunoprecipitation (Co-ip) assays were used to confirm the potential role of PWP1 in Wnt and Hippo signaling pathways.

Results

PWP1 expression in NSCLC was higher than that in normal bronchial epithelium and normal submucosal glands. In addition, PWP1 expression had a positive correlation with poor differentiation, high pathological tumor-node-metastasis (TNM) stage, and lymph node metastasis. Kaplan–Meier database demonstrated that the overall survival time of patients with high PWP1 expression was significantly shorter than that of patients with low PWP1 expression. Mechanistically, we found that PWP1 could interact with DVL2 to upregulate β-catenin (thereby activating the Wnt pathway), whereas PWP1 could interact with Merlin (NF2) to downregulate p-MST1 (thereby inhibiting the Hippo signaling pathway). The effects of PWP1 on promoting the Wnt pathway or inhibiting the Hippo pathway were offset in DVL2- or Merlin-knockdown cells transiently overexpressing PWP1.

Conclusion

PWP1 expression in NSCLC was correlated with poor prognosis. PWP1 enhanced the activity of the Wnt pathway by interacting with DVL2, whereas PWP1 inhibited the activity of the Hippo pathway by interacting with Merlin. Together, these two effects promoted the detrimental biological behaviors of NSCLC cells.

Maintenance of Stem Cell Niche Integrity by a Novel Activator of Integrin Signaling

Stem cells depend critically on the surrounding microenvironment, or niche, for their maintenance and self-renewal. While much is known about how the niche regulates stem cell self-renewal and differentiation, mechanisms for how the niche is maintained over time are not well understood. At the apical tip of the Drosophila testes, germline stem cells (GSCs) and somatic stem cells share a common niche formed by hub cells. Here we demonstrate that a novel protein named Shriveled (Shv) is necessary for the maintenance of hub/niche integrity. Depletion of Shv protein results in age-dependent deterioration of the hub structure and loss of GSCs, whereas upregulation of Shv preserves the niche during aging. We find Shv is a secreted protein that modulates DE-cadherin levels through extracellular activation of integrin signaling. Our work identifies Shv as a novel activator of integrin signaling and suggests a new integration model in which crosstalk between integrin and DE-cadherin in niche cells promote their own preservation by maintaining the niche architecture.

Stem cells are vital for development and for regeneration and repair of tissues in an organism. The ability of adult stem cells to maintain their “stemness” depends critically on the localized microenvironment, or niche. While much is known about how the niche regulates stem cell self-renewal and differentiation, mechanisms for how the niche is maintained during aging are not well understood. Using Drosophila testis as a model system, here we demonstrate that a protein we named Shriveled is a secreted protein that activates integrin signaling to preserve niche architecture. We also show that Shriveled-dependent activation of integrin maintains normal E-cadherin levels in the niche cells, providing a mechanism for niche maintenance. Interestingly, upregulation of Shriveled retards the loss of niche and stem cells seen during normal aging. Together, our work identifies Shriveled as a novel molecule required for preservation of the niche structure in the Drosophila testis.

Specificity and promiscuity in human glutaminase interacting protein recognition: insight from the binding of the internal and C-terminal motif

A large number of cellular processes are mediated by protein-protein interactions, often specified by particular protein binding modules. PDZ domains make up an important class of protein-protein interaction modules that typically bind to the C-terminus of target proteins. These domains act as a scaffold where signaling molecules are linked to a multiprotein complex. Human glutaminase interacting protein (GIP), also known as tax interacting protein 1, is unique among PDZ domain-containing proteins because it is composed almost exclusively of a single PDZ domain rather than one of many domains as part of a larger protein. GIP plays pivotal roles in cellular signaling, protein scaffolding, and cancer pathways via its interaction with the C-terminus of a growing list of partner proteins. We have identified novel internal motifs that are recognized by GIP through combinatorial phage library screening. Leu and Asp residues in the consensus sequence were identified to be critical for binding to GIP through site-directed mutagenesis studies. Structure-based models of GIP bound to two different surrogate peptides determined from nuclear magnetic resonance constraints revealed that the binding pocket is flexible enough to accommodate either the smaller carboxylate (COO(-)) group of a C-terminal recognition motif or the bulkier aspartate side chain (CH(2)COO(-)) of an internal motif. The noncanonical ILGF loop in GIP moves in for the C-terminal motif but moves out for the internal recognition motifs, allowing binding to different partner proteins. One of the peptides colocalizes with GIP within human glioma cells, indicating that GIP might be a potential target for anticancer therapeutics.

High resolution array in the clinical approach to chromosomal phenotypes

Array genomic hybridization (AGH) has recently been implemented as a diagnostic tool for the detection of submicroscopic copy number variants (CNVs) in patients with developmental disorders. However, there is no consensus regarding the choice of the platform, the minimal resolution needed and systematic interpretation of CNVs. We report our experience in the clinical diagnostic use of high resolution AGH up to 100 kb on 131 patients with chromosomal phenotypes but previously normal karyotype. We evaluated the usefulness in our clinics and laboratories by the detection rate of causal CNVs and CNVs of unknown clinical significance and to what extent their interpretation would challenge the systematic use of high-resolution arrays in clinical application. Prioritizing phenotype-genotype correlation in our interpretation strategy to criteria previously described, we identified 33 (25.2%) potentially pathogenic aberrations. 16 aberrations were confirmed pathogenic (16.4% syndromic, 8.5% non-syndromic patients); 9 were new and individual aberrations, 3 of them were pathogenic although inherited and one is as small as approx 200 kb. 13 of 16 further CNVs of unknown significance were classified likely benign, for 3 the significance remained unclear. High resolution array allows the detection of up to 12.2% of pathogenic aberrations in a diagnostic clinical setting. Although the majority of aberrations are larger, the detection of small causal aberrations may be relevant for family counseling. The number of remaining unclear CNVs is limited. Careful phenotype-genotype correlations of the individual CNVs and clinical features are challenging but remain a hallmark for CNV interpretation.

Survey of the 2009 commercial optical biosensor literature

We took a different approach to reviewing the commercial biosensor literature this year by inviting 22 biosensor users to serve as a review committee. They set the criteria for what to expect in a publication and ultimately decided to use a pass/fail system for selecting which papers to include in this year's reference list. Of the 1514 publications in 2009 that reported using commercially available optical biosensor technology, only 20% passed their cutoff. The most common criticism the reviewers had with the literature was that "the biosensor experiments could have been done better." They selected 10 papers to highlight good experimental technique, data presentation, and unique applications of the technology. This communal review process was educational for everyone involved and one we will not soon forget.