Using the yeast two-hybrid system to identify human epithelial cell proteins that bind gonococcal Opa proteins: intracellular gonococci bind pyruvate kinase via their Opa proteins and require host pyruvate for growth

Neisseria meningitidis activates pyroptotic pathways in a mouse model of meningitis: role of a two-partner secretion system

There is evidence that in infected cells in vitro the meningococcal HrpA/HrpB two-partner secretion system (TPS) mediates the exit of bacteria from the internalization vacuole and the docking of bacteria to the dynein motor resulting in the induction of pyroptosis. In this study we set out to study the role of the HrpA/HrpB TPS in establishing meningitis and activating pyroptotic pathways in an animal model of meningitis using a reference serogroup C meningococcal strain, 93/4286, and an isogenic hrpB knockout mutant, 93/4286ΩhrpB. Survival experiments confirmed the role of HrpA/HrpB TPS in the invasive meningococcal disease. In fact, the ability of the hrpB mutant to replicate in brain and spread systemically was impaired in mice infected with hrpB mutant. Furthermore, western blot analysis of brain samples during the infection demonstrated that: i. N. meningitidis activated canonical and non-canonical inflammasome pyroptosis pathways in the mouse brain; ii. the activation of caspase-11, caspase-1, and gasdermin-D was markedly reduced in the hrpB mutant; iii. the increase in the amount of IL-1β and IL-18, which are an important end point of pyroptosis, occurs in the brains of mice infected with the wild-type strain 93/4286 and is strongly reduced in those infected with 93/4286ΩhrpB. In particular, the activation of caspase 11, which is triggered by cytosolic lipopolysaccharide, indicates that during meningococcal infection pyroptosis is induced by intracellular infection after the exit of the bacteria from the internalizing vacuole, a process that is hindered in the hrpB mutant. Overall, these results confirm, in an animal model, that the HrpA/HrpB TPS plays a role in the induction of pyroptosis and suggest a pivotal involvement of pyroptosis in invasive meningococcal disease, paving the way for the use of pyroptosis inhibitors in the adjuvant therapy of the disease.

Dinner date: Neisseria gonorrhoeae central carbon metabolism and pathogenesis

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhea, is a human-adapted pathogen that does not productively infect other organisms. The ongoing relationship between N. gonorrhoeae and the human host is facilitated by the exchange of nutrient resources that allow for N. gonorrhoeae growth in the human genital tract. What N. gonorrhoeae 'eats' and the pathways used to consume these nutrients have been a topic of investigation over the last 50 years. More recent investigations are uncovering the impact of N. gonorrhoeae metabolism on infection and inflammatory responses, the environmental influences driving N. gonorrhoeae metabolism, and the metabolic adaptations enabling antimicrobial resistance. This mini-review is an introduction to the field of N. gonorrhoeae central carbon metabolism in the context of pathogenesis. It summarizes the foundational work used to characterize N. gonorrhoeae central metabolic pathways and the effects of these pathways on disease outcomes, and highlights some of the most recent advances and themes under current investigation. This review ends with a brief description of the current outlook and technologies under development to increase understanding of how the pathogenic potential of N. gonorrhoeae is enabled by metabolic adaptation.

Transcriptome-guided metabolic network analysis reveals rearrangements of carbon flux distribution in Neisseria gonorrhoeae during neutrophil co-culture

The ability of bacterial pathogens to metabolically adapt to the environmental conditions of their hosts is critical to both colonization and invasive disease. Infection with Neisseria gonorrhoeae (the gonococcus, Gc) is characterized by the influx of neutrophils [polymorphonuclear leukocytes (PMNs)], which fail to clear the bacteria and make antimicrobial products that can exacerbate tissue damage. The inability of the human host to clear Gc infection is particularly concerning in light of the emergence of strains that are resistant to all clinically recommended antibiotics. Bacterial metabolism represents a promising target for the development of new therapeutics against Gc. Here, we generated a curated genome-scale metabolic network reconstruction (GENRE) of Gc strain FA1090. This GENRE links genetic information to metabolic phenotypes and predicts Gc biomass synthesis and energy consumption. We validated this model with published data and in new results reported here. Contextualization of this model using the transcriptional profile of Gc exposed to PMNs revealed substantial rearrangements of Gc central metabolism and induction of Gc nutrient acquisition strategies for alternate carbon source use. These features enhanced the growth of Gc in the presence of neutrophils. From these results, we conclude that the metabolic interplay between Gc and PMNs helps define infection outcomes. The use of transcriptional profiling and metabolic modeling to reveal new mechanisms by which Gc persists in the presence of PMNs uncovers unique aspects of metabolism in this fastidious bacterium, which could be targeted to block infection and thereby reduce the burden of gonorrhea in the human population. IMPORTANCE The World Health Organization designated Gc as a high-priority pathogen for research and development of new antimicrobials. Bacterial metabolism is a promising target for new antimicrobials, as metabolic enzymes are widely conserved among bacterial strains and are critical for nutrient acquisition and survival within the human host. Here we used genome-scale metabolic modeling to characterize the core metabolic pathways of this fastidious bacterium and to uncover the pathways used by Gc during culture with primary human immune cells. These analyses revealed that Gc relies on different metabolic pathways during co-culture with human neutrophils than in rich media. Conditionally essential genes emerging from these analyses were validated experimentally. These results show that metabolic adaptation in the context of innate immunity is important to Gc pathogenesis. Identifying the metabolic pathways used by Gc during infection can highlight new therapeutic targets for drug-resistant gonorrhea.

Identification of Differentially Expressed Genes Related to the Lipid Metabolism of Esophageal Squamous Cell Carcinoma by Integrated Bioinformatics Analysis

Purpose: In recent years, lipid metabolism has been reprogrammed to meet the energy and substrate needs of tumorigenesis and development and is a potential new target for cancer treatment. However, the regulatory mechanism of lipid metabolism in esophageal squamous cell carcinoma is not well understood. Methods: We first downloaded the esophageal squamous cell carcinoma (ESCC) gene dataset in the GEO and TCGA databases and analyzed the central differentially expressed genes (DEGs) of ESCC through bioinformatics. Afterwards, the GSEA method was used to analyze the lipid metabolism-related pathway of the central gene in the pathological process of ESCC, and it was determined that the central gene OIP5 was significantly related to the fatty acid metabolism pathway. Our heatmap also revealed that the enrichment of the ACSL family in ESCC tissues was more pronounced than in normal tissues. We hypothesized that OIP5 can regulate the fatty acid metabolism process in ESCC cells and affect the tumorigenic ability of ESCC. Further statistical analysis and experiment were conducted to determine the lipid metabolism-related gene, OIP5′s, expression pattern and clinical significance in ESCC, analyze the effect of OIP5 expression on fatty acid metabolism-related enzymes in ESCC, revealing the specific mechanism of OIP5 that promotes ESCC development. Conclusions: Our study established a correlation between OIP5 expression and clinicopathological factors (tumor size, T stage, N stage, and clinical grade) in esophageal squamous cell carcinoma (p < 0.05). We have also experimentally demonstrated that OIP5 regulates ESCC fatty acid metabolism by influencing the expression of the key enzyme ACSL1 in lipid metabolism.

Research progress on the role of PKM2 in the immune response

Pyruvate kinase (PK) is a key enzyme that catalyzes the dephosphorylation of phosphoenolpyruvate (PEP) into pyruvate, and is responsible for the production of ATP during glycolysis. As another important isozyme of PK, pyruvate kinase M2 (PKM2) exists in cells with high levels of nucleic acid synthesis, such as normal proliferating cells (e.g., lymphocytes and intestinal epithelial cells), embryonic cells, adult stem cells, and tumor cells. With further research, PKM2, as an important regulator of cellular pathophysiological activity, has attracted increasing attention in the process of autoimmune response and inflammatory. In this re]view, we examine the contribution of PKM2 to the human immune response. Further studies on the immune mechanisms of PKM2 are expected to provide more new ideas and drug targets for immunotherapy of inflammatory and autoimmune diseases, guiding drug development and disease treatment.

Aberrant Gene Expression Profiling in Men With Sertoli Cell-Only Syndrome

Sertoli cell-only syndrome (SCOS) is the most severe and common pathological type of non-obstructive azoospermia. The etiology of SCOS remains largely unknown to date despite a handful of studies reported in this area. According to the gene expression of testicular tissue samples in six datasets from the Gene Expression Omnibus, we detected 1441 differentially expressed genes (DEGs) between SCOS and obstructive azoospermia (OA) testicular tissue samples. Enriched GO terms and KEGG pathways for the downregulated genes included various terms and pathways related to cell cycle and reproduction, while the enrichment for the upregulated genes yielded many inflammation-related terms and pathways. In accordance with the protein-protein interaction (PPI) network, all genes in the most critical module belonged to the downregulated DEGs, and we obtained nine hub genes, including CCNB1, AURKA, CCNA2, BIRC5, TYMS, UBE2C, CDC20, TOP2A, and OIP5. Among these hub genes, six were also found in the most significant SCOS-specific module obtained from consensus module analysis. In addition, most of SCOS-specific modules did not have a consensus counterpart. Based on the downregulated genes, transcription factors (TFs) and kinases within the upstream regulatory network were predicted. Then, we compared the difference in infiltrating levels of immune cells between OA and SCOS samples and found a significantly higher degree of infiltration for most immune cells in SCOS than OA samples. Moreover, CD56bright natural killer cell was significantly associated with six hub genes. Enriched hallmark pathways in SCOS had remarkably more upregulated pathways than the downregulated ones. Collectively, we detected DEGs, significant modules, hub genes, upstream TFs and kinases, enriched downstream pathways, and infiltrated immune cells that might be specifically implicated in the pathogenesis of SCOS. These findings provide new insights into the pathogenesis of SCOS and fuel future advances in its theranostics.

OIP5 Is a Novel Prognostic Biomarker in Clear Cell Renal Cell Cancer Correlating With Immune Infiltrates

Opa interacting protein 5 (OIP5), overexpressed in some types of human cancers, has been reported to be associated with the carcinogenesis of human cancer. However, its contribution to cancer immunity remains unknown. Furthermore, the relationship between OIP5 and cancer immunity remains uncertain. In our research, we explored the different expression of OIP5 between 539 ccRCC and 72 normal renal tissues base on TCGA data set. We analyzed the associations between OIP5 expression with ccRCC progression and survival. Next, we compared immune cell profiles in cancer tissues and normal tissues in the Cancer Genome Atlas (TCGA) ccRCC cohort. We found that the level of immune cell infiltration was correlated with the copy number of OIP5 gene in ccRCC. The effect of OIP5 on immune activity was verified by Gene Set Enrichment Analysis of RNA-seq data from 32 ccRCC cell lines in the public database. Moreover, a pathway enrichment analysis of 49 OIP5-associated immunomodulators demonstrated the involvement of the T cell receptor signaling pathway, the JAK-STAT signaling pathway, the NF-kappa B signaling pathway and the primary immunodeficiency pathway. In addition, using OIP5-associated immunomodulators, we constructed multiple-gene risk prediction signatures using the Cox regression model. Our results provided insights into the role of OIP5 in tumor immunity and revealed that OIP5 may be a potential immunotherapeutic target for ccRCC. Designated immune signature is a promising prognostic biomarker in ccRCC.

Neisseria gonorrhoeae physiology and pathogenesis

Neisseria gonorrhoeae is an obligate human pathogen that is the cause of the sexually transmitted disease gonorrhoea. Recently, there has been a surge in gonorrhoea cases that has been exacerbated by the rapid rise in gonococcal multidrug resistance to all useful antimicrobials resulting in this organism becoming a significant public health burden. Therefore, there is a clear and present need to understand the organism's biology through its physiology and pathogenesis to help develop new intervention strategies. The gonococcus initially colonises and adheres to host mucosal surfaces utilising a type IV pilus that helps with microcolony formation. Other adhesion strategies include the porin, PorB, and the phase variable outer membrane protein Opa. The gonococcus is able to subvert complement mediated killing and opsonisation by sialylation of its lipooligosaccharide and deploys a series of anti-phagocytic mechanisms. N. gonorrhoeae is a fastidious organism that is able to grow on a limited number of primary carbon sources such as glucose and lactate. The utilization of lactate by the gonococcus has been implicated in a number of pathogenicity mechanisms. The bacterium lives mainly in microaerobic environments and can grow both aerobically and anaerobically with the aid of nitrite. The gonococcus does not produce siderophores for scavenging iron but can utilize some produced by other bacteria, and it is able to successful chelate iron from host haem, transferrin and lactoferrin. The gonococcus is an incredibly versatile human pathogen; in the following chapter, we detail the intricate mechanisms used by the bacterium to invade and survive within the host.

A Perspective on Medicinal Chemistry Approaches for Targeting Pyruvate Kinase M2

The allosteric regulation of pyruvate kinase M2 (PKM2) affects the switching of the PKM2 protein between the high-activity and low-activity states that allow ATP and lactate production, respectively. PKM2, in its low catalytic state (dimeric form), is chiefly active in metabolically energetic cells, including cancer cells. More recently, PKM2 has emerged as an attractive target due to its role in metabolic dysfunction and other interrelated conditions. PKM2 (dimer) activity can be inhibited by modulating PKM2 dimer-tetramer dynamics using either PKM2 inhibitors that bind at the ATP binding active site of PKM2 (dimer) or PKM2 activators that bind at the allosteric site of PKM2, thus activating PKM2 from the dimer formation to the tetrameric formation. The present perspective focuses on medicinal chemistry approaches to design and discover PKM2 inhibitors and activators and further provides a scope for the future design of compounds targeting PKM2 with better efficacy and selectivity.

Prognostic and Therapeutic Potential of the OIP5 Network in Papillary Renal Cell Carcinoma

Papillary renal cell carcinoma (pRCC) is an aggressive but minor type of RCC. The current understanding and management of pRCC remain poor. We report here OIP5 being a novel oncogenic factor and possessing robust prognostic values and therapeutic potential. OIP5 upregulation is observed in pRCC. The upregulation is associated with pRCC adverse features (T1P < T2P < CIMP, Stage1 + 2 < Stage 3 < Stage 4, and N0 < N1) and effectively stratifies the fatality risk. OIP5 promotes ACHN pRCC cell proliferation and xenograft formation; the latter is correlated with network alterations related to immune regulation, metabolism, and hypoxia. A set of differentially expressed genes (DEFs) was derived from ACHN OIP5 xenografts and primary pRCCs (n = 282) contingent to OIP5 upregulation; both DEG sets share 66 overlap genes. Overlap66 effectively predicts overall survival (p < 2 × 10^-16) and relapse (p < 2 × 10^-16) possibilities. High-risk tumors stratified by Overlap66 risk score possess an immune suppressive environment, evident by elevations in Treg cells and PD1 in CD8 T cells. Upregulation of PLK1 occurs in both xenografts and primary pRCC tumors with OIP5 elevations. PLK1 displays a synthetic lethality relationship with OIP5. PLK1 inhibitor BI2356 inhibits the growth of xenografts formed by ACHN OIP5 cells. Collectively, the OIP5 network can be explored for personalized therapies in management of pRCC patients.

Raf1 interacts with OIP5 to participate in oxaliplatin-induced neuropathic pain

AIMS

Oxaliplatin is an effective anti-cancer platinum-based chemotherapy drug which can cause severe chronic neuropathy, but the molecular mechanism underlying this adverse effect is still unclear. Opa interacting protein 5 (OIP5) is a member of the cancer/testis antigen (CTA) family and is involved in a variety of cancers. Studies have shown that Raf1, which is a serine/threonine-protein kinase, can directly combine with OIP5 to promote its expression. Whether Raf1 and OIP5 can participate in oxaliplatin-induced neuropathic pain has not been reported.

MAIN METHODS

In this study, the oxaliplatin-induced neuropathic pain model was prepared by intraperitoneal injection of oxaliplatin. OIP5 and Raf1 were knocked down by intrathecal injection of siRNA against Raf1 and OIP5 (siRaf1, siOIP5). Von Frey fiber and acetone were used to detect pain behavior, and western blot was used to detect the protein expression changes of OIP5 and Raf1 in the dorsal root ganglion (DRG).

KEY FINDINGS

The expression levels of p-Raf1 and OIP5 were increased in DRGs of oxaliplatin-induced neuropathic pain rats. Intrathecal administration of siOIP5 to inhibit the expression of OIP5 not only effectively alleviated oxaliplatin-induced mechanical allodynia and cold hyperalgesia, but also decreased the protein expression of Raf1. Intrathecal administration of siRaf1 inhibited the expression of OIP5 and attenuated oxaliplatin-induced neuropathic pain.

SIGNIFICANCE

This study confirmed that Raf1 interacts with OIP5 to participate in oxaliplatin-induced neuropathic pain. The restricted expression of OIP5 in normal tissues may make it an ideal drug target for the treatment of oxaliplatin-induced neuropathic pain.

Regulation of the tubulin polymerization-promoting protein by Ca2+/S100 proteins

To elucidate S100 protein-mediated signaling pathways, we attempted to identify novel binding partners for S100A2 by screening protein arrays carrying 19,676 recombinant glutathione S-transferase (GST)-fused human proteins with biotinylated S100A2. Among newly discovered putative S100A2 interactants, including TMLHE, TRH, RPL36, MRPS34, CDR2L, OIP5, and MED29, we identified and characterized the tubulin polymerization-promoting protein (TPPP) as a novel S100A2-binding protein. We confirmed the interaction of TPPP with Ca²⁺/S100A2 by multiple independent methods, including the protein array method, S100A2 overlay, and pulldown assay in vitro and in transfected COS-7 cells. Based on the results from the S100A2 overlay assay using various GST-TPPP mutants, the S100A2-binding region was identified in the C-terminal (residues 111-160) of the central core domain of a monomeric form of TPPP that is involved in TPPP dimerization. Chemical cross-linking experiments indicated that S100A2 suppresses dimer formation of His-tagged TPPP in a dose-dependent and a Ca²⁺-dependent manner. In addition to S100A2, TPPP dimerization is disrupted by other multiple S100 proteins, including S100A6 and S100B, in a Ca²⁺-dependent manner but not by S100A4. This is consistent with the fact that S100A6 and S100B, but not S100A4, are capable of interacting with GST-TPPP in the presence of Ca²⁺. Considering these results together, TPPP was identified as a novel target for S100A2, and it is a potential binding target for other multiple S100 proteins, including S100A6 and S100B. Direct binding of the S100 proteins with TPPP may cause disassembly of TPPP dimer formation in response to the increasing concentration of intracellular Ca²⁺, thus resulting in the regulation of the physiological function of TPPP, such as microtubule organization.

Epitope Analysis of Murine and Chimeric Monoclonal Antibodies Recognizing the Cancer Testis Antigen PRAME

We investigated the epitope specificity of different monoclonal antibodies recognizing the cancer testis antigen PRAME. Antibody 5D3 binds to the fragment of PRAME corresponding to 160-180 amino acid residues. Antibodies 6H8 and F11 bind to the fragment corresponding to 180-200 amino acid residues of PRAME. These antibodies retained the ability to recognize these PRAME fragments after chimerization.

Opa-Interacting Protein 5 Expression in Human Glioma Tissues Is Essential to the Biological Function of U251 Human Malignant Glioma Cells

Opa-interacting protein 5 (OIP5) is a member of the cancer-testis antigen (CTA) family that elicits a spontaneous antitumor immune response. The failure of current immunotherapies for glioma has prompted the search for novel biomarkers that may be utilized as therapeutic targets. This study aimed to investigate whether OIP5 serves as a target for malignant glioma immunotherapy. Glioma specimens from 53 adult patients were evaluated for OIP5 expression by immunohistochemical (IHC) staining, and the correlation of OIP5 expression with World Health Organization (WHO) tumor grade was analyzed. Endogenous expression of OIP5 in glioma cell lines was determined via real-time polymerase chain reaction (RT-PCR). Using lentiviral siOIP5, the effect of OIP5 gene knockdown on proliferation, cell cycle, and apoptosis in U251 glioma cells was studied. The results show that OIP5 is overexpressed in glioma tissues and is correlated with WHO tumor grade (P < 0.001). However, OIP5 protein expression is barely detectable in normal adult brain tissues. MTT assays and analysis using the Celigo Imaging Cytometry System reveal that the silencing of OIP5 inhibits U251 cell growth. Cell cycle assays and Annexin V staining show that OIP5 silencing disrupts the balance of the cell cycle and increases U251 cell death. These results indicate that OIP5 is upregulated in malignant glioma specimens but barely detected in normal brain tissues. OIP5 knockdown inhibits the biological function of glioma cells, reinforcing that OIP5 may serve as an immunotherapeutic target for malignant glioma.

Cancer-testis specific gene OIP5: a downstream gene of E2F1 that promotes tumorigenesis and metastasis in glioblastoma by stabilizing E2F1 signaling

Background

The cancer-testis specific gene Opa interacting protein 5 (OIP5) is reactivated in many human cancers, but its functions in glioblastoma remain unclear. Here, we assessed the significance of OIP5 in the tumorigenesis and metastasis of glioblastoma for the first time.

Methods

An immunohistochemistry assay was performed to detect OIP5 expression changes in glioblastoma patients. Overall survival analysis was performed to evaluate the prognostic significance of OIP5. Growth curve, colony formation, and transwell assays were used to analyze cell proliferation and metastasis. Tumorigenicity potential was investigated in orthotopic tumor models, and immunoprecipitation, chromatin immunoprecipitation, and luciferase assays were employed to explore the mechanisms underlying the activation of OIP5 expression by E2F transcription factor 1 (E2F1) to stabilize and maintain E2F1 signaling.

Results

OIP5 was found to be upregulated in glioblastoma patients and to impair patient survival, and the increased expression of OIP5 was positively correlated with tumor stage. Compared with short hairpin green fluorescent protein cells, cells in which OIP5 was knocked down exhibited significantly reduced proliferation, metastasis, colony formation, and tumorigenicity abilities, whereas OIP5 recovery enhanced these abilities. OIP5 was highly correlated with cell cycle progression but had no obvious effects on apoptosis. Notably, we demonstrated a feedback loop in which E2F1 activates the expression of OIP5 to stabilize and maintain E2F1 signaling and promote the E2F1-regulated gene expression that is required for aggressive tumor biology.

Conclusions

Collectively, our findings demonstrate that OIP5 promotes glioblastoma progression and metastasis, suggesting that OIP5 is a potential target for anticancer therapy.

Cancer Testis Antigens and Immunotherapy: Where Do We Stand in the Targeting of PRAME?

PRAME or PReferentially expressed Antigen in Melanoma is a testis-selective cancer testis antigen (CTA) with restricted expression in somatic tissues and re-expression in various cancers. It is one of the most widely studied CTAs and has been associated with the outcome and risk of metastasis. Although little is known about its pathophysiological function, PRAME has gained interest as a candidate target for immunotherapy. This review provides an update on our knowledge on PRAME expression and function in healthy and malignant cells and the current immunotherapeutic strategies targeting PRAME with their specific challenges and opportunities. We also highlight some of the features that position PRAME as a unique cancer testis antigen to target.

Identifying novel biomarkers in hepatocellular carcinoma by weighted gene co-expression network analysis

Hepatocellular carcinoma (HCC) is a highly malignant tumor found in the bile duct epithelial cells, and the second most common tumor of the liver. However, the pivotal roles of most molecules of tumorigenesis in HCC are still unclear. Hence, it is essential to detect the tumorigenic mechanism and develop novel prognostic biomarkers for clinical application. The data of HCC mRNA-seq and clinical information from The Cancer Genome Atlas (TCGA) database were analyzed by weighted gene co-expression network analysis (WGCNA). Co-expression modules and clinical traits were constructed by the Pearson correlation analysis, interesting modules were selected and gene ontology and pathway enrichment analysis were performed. Intramodule analysis and protein-protein interaction construction of selected modules were conducted to screen hub genes. In addition, upstream transcription factors and microRNAs of hub genes were predicted by miRecords and NetworkAnalyst database. Afterward, a high connectivity degree of hub genes from two networks was picked out to perform the differential expression validation in the Gene Expression Profiling Interactive Analysis database and Human Protein Atlas database and survival analysis in Kaplan-Meier plotter online tool. By utilizing WGCNA, several hub genes that regulate the mechanism of tumorigenesis in HCC were identified, which was associated with clinical traits including the pathological stage, histological grade, and liver function. Surprisingly, ZWINT, CENPA, RACGAP1, PLK1, NCAPG, OIP5, CDCA8, PRC1, and CDK1 were identified statistically as hub genes in the blue module, which were closely implicated in pathological T stage and histologic grade of HCC. Moreover, these genes also were strongly associated with the HCC cell growth and division. Network and survival analyses found that nine hub genes may be considered theoretically as indicators to predict the prognosis of patients with HCC or clinical treatment target, it will be necessary for basic experiments and large-scale cohort studies to validate further.

Overexpression of Opa interacting protein 5 increases the progression of liver cancer via BMPR2/JUN/CHEK1/RAC1 dysregulation

Opa interacting protein 5 (OIP5) overexpression is associated with human carcinoma. However, its biological function, underlying mechanism and clinical significance in liver cancer remain unknown. In the present study, the effects of OIP5 expression on liver cancer, and the mechanisms regulating these effects, were investigated. OIP5 expression was measured in human hepatocellular carcinoma (HCC) tissues and liver cancer cell lines. The effect of OIP5 knockdown on tumorigenesis was also detected in nude mice, and differentially‑expressed genes (DEGs) were identified and their biological functions were identified. The results indicated that OIP5 expression was significantly upregulated in HCC tissues and four liver cancer cell lines (P<0.01). Increased OIP5 protein expression significantly predicted reduced survival rate of patients with HCC (P<0.01). OIP5 knockdown resulted in the suppression of proliferation and colony forming abilities, cell cycle arrest at the G0/G1 or G2/M phases, and promotion of cell apoptosis. A total of 628 DEGs, including 87 upregulated and 541 downregulated genes, were identified following OIP5 knockdown. Functional enrichment analysis indicated that DEGs were involved in 'RNA Post‑Transcriptional Modification, Cancer and Organismal Injury and Abnormalities'. Finally, OIP5 knockdown in Huh7 cells dysregulated bone morphogenetic protein receptor type 2/JUN/checkpoint kinase 1/Rac family small GTPase 1 expression. In conclusion, the overall results demonstrated the involvement of OIP5 in the progression of liver cancer and its mechanism of action.

Weighted gene co‑expression network analysis for identifying hub genes in association with prognosis in Wilms tumor

Wilms tumor (WT) is the most common type of renal malignancy in children. Survival rates are low and high-risk WT generally still carries a poor prognosis. To better elucidate the pathogenesis and tumorigenic pathways of high-risk WT, the present study presents an integrated analysis of RNA expression profiles of high-risk WT to identify predictive molecular biomarkers, for the improvement of therapeutic decision-making. mRNA sequence data from high-risk WT and adjacent normal samples were downloaded from The Cancer Genome Atlas to screen for differentially expressed genes (DEGs) using R software. From 132 Wilms tumor samples and six normal samples, 2,089 downregulated and 941 upregulated DEGs were identified. In order to identify hub DEGs that regulate target genes, weighted gene co-expression network analysis (WGCNA) was used to identify 11 free-scale gene co-expressed clusters. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were annotated using KEGG Orthology Based Annotation System annotation of different module genes. The Search Tool for the Retrieval of Interacting Genes was used to construct a protein-protein interaction network for the identified DEGs, and the hub genes of WGCNA modules were identified using the Cytohubb plugin with Cytoscape software. Survival analysis was subsequently performed to highlight hub genes with a clinical signature. The present results suggest that epidermal growth factor, cyclin dependent kinase 1, endothelin receptor type A, nerve growth factor receptor, opa-interacting protein 5, NDC80 kinetochore complex component and cell division cycle associated 8 are essential to high-risk WT pathogenesis, and they are closely associated with clinical prognosis.

OIP5 Promotes Growth, Metastasis and Chemoresistance to Cisplatin in Bladder Cancer Cells

Opa interacting protein 5 (OIP5) has previously been identified as a tumorigenesis gene. The purpose of this study is to explore the role of OIP5 in the progression of bladder cancer (BC). The OIP5 expression and clinical behaviors in bladder cancer were collected from lager database. Our study showed that OIP5 was highly expressed in bladder cancer tissues and cells. Overexpression of OIP5 in tumor patients predicted worse overall survival (OS) and higher histological grade. Vitro and vivo experiments demonstrated that knockdown of OIP5 significantly inhibited cell growth of BC. Scratch assay and transwell assay suggested that migration capacity of BC cells was decreased after knockdown of OIP5. Cisplatin sensitivity assay indicated that depletion of OIP5 increased the sensitivity of BC cells to cisplatin. Finally, we identified 38 overlapping differentially expressed genes (DEGs) between RNA-seq and TCGA analyses which were closely linked to OIP5. Bioinformatics analysis showed that these DEGs enriched in oocyte meiosis, fanconi anemia pathway, cell cycle, and microRNAs regulation. TOP2A, SPAG5, SKA1, EXO1, TK1 were confirmed to associated with bladder cancer development. Our study suggests that OIP5 may be a potential biomarker for growth, metastasis and drug-resistance in bladder cancer.

PKM2 Is Required to Activate Myeloid Dendritic Cells from Patients with Severe Aplastic Anemia

Severe aplastic anemia (SAA) is an autoimmune disease in which bone marrow failure is mediated by activated myeloid dendritic cells (mDCs) and T lymphocytes. Recent research has identified a strong immunomodulatory effect of pyruvate kinase M2 (PKM2) on dendritic cells in immune-mediated diseases. In this study, we aimed to explore the role of PKM2 in the activation of mDCs in SAA. We observed conspicuously higher levels of PKM2 in mDCs from SAA patients compared to normal controls at both the gene and protein levels. Concurrently, we unexpectedly discovered that after the mDC-specific downregulation of PKM2, mDCs from patients with SAA exhibited weakened phagocytic activity and significantly decreased and shortened dendrites relative to their counterparts from normal controls. The expression levels of the costimulatory molecules CD86 and CD80 were also reduced on mDCs. Our results also suggested that PKM2 knockdown in mDCs reduced the abilities of these cells to promote the activation of CD8+ T cells (CTLs), leading to the decreased secretion of cytotoxic factors by the latter cell type. These findings demonstrate that mDC activation requires an elevated intrinsic PKM2 level and that PKM2 improves the immune status of patients with SAA by enhancing the functions of mDCs and, consequently, CTLs.

Opa-interacting protein 5 modulates docetaxel-induced cell death via regulation of mitophagy in gastric cancer

Damage to mitochondria induces mitophagy, a cellular process that is gaining interest for its therapeutic relevance to a variety of human diseases. However, the mechanism underlying mitochondrial depolarization and clearance in mitophagy remains poorly understood. We previously reported that mitochondria-induced cell death was caused by knockdown of Neisseria gonorrhoeae opacity-associated-interacting protein 5 in gastric cancer. In this study, we show that Neisseria gonorrhoeae opacity-associated-interacting protein 5 loss and gain of function modulates mitophagy induced by treatment with docetaxel, a chemotherapy drug for gastric cancer. The activation of mitophagy by Neisseria gonorrhoeae opacity-associated-interacting protein 5 overexpression promoted cell survival, preventing docetaxel-induced mitochondrial clearance. Conversely, short interfering RNA-mediated knockdown of Neisseria gonorrhoeae opacity-associated-interacting protein 5 accelerated docetaxel-induced apoptosis while increasing mitochondrial depolarization, reactive oxygen species, and endoplasmic reticulum stress and decreasing adenosine triphosphate production. We also found that the mitochondrial outer membrane proteins mitofusin 2 and phosphatase and tensin homolog-induced putative kinase 1 colocalized with Neisseria gonorrhoeae opacity-associated-interacting protein 5 in mitochondria and that mitofusin 2 knockdown altered Neisseria gonorrhoeae opacity-associated-interacting protein 5 expression. These findings indicate that Neisseria gonorrhoeae opacity-associated-interacting protein 5 modulates docetaxel-induced mitophagic cell death and therefore suggest that this protein comprises a potential therapeutic target for gastric cancer treatment.

OIP5, a target of miR-15b-5p, regulates hepatocellular carcinoma growth and metastasis through the AKT/mTORC1 and β-catenin signaling pathways

Opa interacting protein 5 (OIP5) is upregulated in some types of human cancers, but the biological implications of its upregulation have not yet been clarified in human hepatocellular carcinoma (HCC). In this study, the signaling pathway downstream of OIP5 was analyzed by proteome kinase profiling. A putative microRNA targeting OIP5 was identified using a miRNA PCR array. Tumorigenicity and metastatic ability were examined in an orthotopic animal model. OIP5 expression was strongly detected in early and advanced tumors via gene expression profiling and immunohistochemical staining analyses. Cells with knockdown of OIP5 via target shRNA exhibited reduced hepatic mass formation and metastatic tumor nodules in an orthotopic mouse model. OIP5-induced AKT activation was mediated by both mTORC2 and p38/PTEN activation. AKT activation was linked to mTORC1 and GSK-3β/β-catenin signaling, which are primarily associated with tumor cell growth and metastasis, respectively. miR-15b-5p, which targets OIP5, efficiently inhibited OIP5-mediated mTORC1 and GSK-3β/β-catenin signaling. These findings suggest that OIP5 may be involved in HCC growth and metastasis and that miR-15b-5p inhibits OIP5-mediated oncogenic signaling in HCC.

Contrasting within- and between-host immune selection shapes Neisseria Opa repertoires

Pathogen evolution is influenced strongly by the host immune response. Previous studies of the effects of herd immunity on the population structure of directly transmitted, short-lived pathogens have primarily focused on the impact of competition for hosts. In contrast, for long-lived infections like HIV, theoretical work has focused on the mechanisms promoting antigenic variation within the host. In reality, successful transmission requires that pathogens balance both within- and between-host immune selection. The Opa adhesins in the bacterial Neisseria genus provide a unique system to study the evolution of the same antigens across two major pathogens: while N. meningitidis is an airborne, respiratory pathogen colonising the nasopharynx relatively transiently, N. gonorrhoeae can cause sexually transmitted, long-lived infections. We use a simple mathematical model and genomic data to show that trade-offs between immune selection pressures within- and between-hosts can explain the contrasting Opa repertoires observed in meningococci and gonococci.

Possible involvement of Opa-interacting protein 5 in adipose proliferation and obesity

Obesity is an epidemic matter increasing risk for cardiovascular diseases and metabolic disorders such as type 2 diabetes. We recently examined the association between visceral fat adiposity and gene expression profile of peripheral blood cells in human subjects. In a series of studies, Opa (Neisseria gonorrhoeae opacity-associated)-interacting protein 5 (OIP5) was nominated as a molecule of unknown function in adipocytes and thus the present study was performed to investigate the role of OIP5 in obesity. Adenovirus overexpressing Oip5 (Ad-Oip5) was generated and infected to 3T3-L1 cells stably expressing Coxsackie-Adenovirus Receptor (CAR-3T3-L1) and to mouse subcutaneous fat. For a knockdown experiment, siRNA against Oip5 (Oip5-siRNA) was introduced into 3T3-L1 cells. Proliferation of adipose cells was measured by BrdU uptake, EdU-staining, and cell count. Significant increase of Oip5 mRNA level was observed in obese white adipose tissues and such increase was detected in both mature adipocytes fraction and stromal vascular cell fraction. Ad-Oip5-infected CAR-3T3-L1 preadipocytes and adipocytes proliferated rapidly, while a significant reduction of proliferation was observed in Oip5-siRNA-introduced 3T3-L1 preadipocytes. Fat weight and number of adipocytes were significantly increased in Ad-Oip5-administered fat tissues. Oip5 promotes proliferation of pre- and mature-adipocytes and contributes adipose hyperplasia. Increase of Oip5 may associate with development of obesity.

Expression of Opa interacting protein 5 (OIP5) is associated with tumor stage and prognosis of clear cell renal cell carcinoma

Opa interacting protein 5 (OIP5), overexpressed in some types of human cancers, has been reported to be associated with the carcinogenesis of human cancer. However, the biological function and clinical significance of OIP5 in human Clear Cell Renal Cell Carcinoma (CCRCC) remains unknown. In the present study, we found the expression of OIP5 was markedly upregulated in surgical CCRCC specimens and CCRCC cell lines. Immunohistochemical analysis revealed that paraffin-embedded archival CCRCC specimens exhibited higher levels of OIP5 expression than normal renal tissues. Further statistical analysis suggested the upregulation of OIP5 was positively correlated with the Fuhrman grade (P = 0.02), T classification (P = 0.015), N classification (P = 0.018) and clinical stage (P = 0.035). Also, patients with high OIP5 expression dramatically exhibited shorter survival time (P = 0.001). In addition, the OIP5 expression was an independent prognostic marker of overall survival of CCRCC patients in a multivariate analysis (P = 0.008). Experimentally, we demonstrated that silencing OIP5 in CCRCC cell lines by specific siRNA clearly inhibited cell growth. In conclusion, our findings suggested that OIP5 could be a valuable marker of CCRCC progression and prognosis, and a promising therapeutic target for CCRCC.

Pyruvate kinase M2: multiple faces for conferring benefits on cancer cells

The M2 splice isoform of pyruvate kinase (PKM2), an enzyme that catalyzes the later step of glycolysis, is a key regulator of aerobic glycolysis (known as the Warburg effect) in cancer cells. Expression and low enzymatic activity of PKM2 confer on cancer cells the glycolytic phenotype, which promotes rapid energy production and flow of glycolytic intermediates into collateral pathways to synthesize nucleic acids, amino acids, and lipids without the accumulation of reactive oxygen species. PKM2 enzymatic activity has also been shown to be negatively regulated by the interaction with CD44 adhesion molecule, which is a cell surface marker for cancer stem cells. In addition to the glycolytic functions, nonglycolytic functions of PKM2 in cancer cells are of particular interest. PKM2 is induced translocation into the nucleus, where it activates transcription of various genes by interacting with and phosphorylating specific nuclear proteins, endowing cancer cells with a survival and growth advantage. Therefore, inhibitors and activators of PKM2 are well underway to evaluate their anticancer effects and suitability for use as novel therapeutic strategies.

PRAME is a golgi-targeted protein that associates with the Elongin BC complex and is upregulated by interferon-gamma and bacterial PAMPs

Preferentially expressed antigen in melanoma (PRAME) has been described as a cancer-testis antigen and is associated with leukaemias and solid tumours. Here we show that PRAME gene transcription in leukaemic cell lines is rapidly induced by exposure of cells to bacterial PAMPs (pathogen associated molecular patterns) in combination with type 2 interferon (IFNγ). Treatment of HL60 cells with lipopolysaccharide or peptidoglycan in combination with IFNγ resulted in a rapid and transient induction of PRAME transcription, and increased association of PRAME transcripts with polysomes. Moreover, treatment with PAMPs/IFNγ also modulated the subcellular localisation of PRAME proteins in HL60 and U937 cells, resulting in targeting of cytoplasmic PRAME to the Golgi. Affinity purification studies revealed that PRAME associates with Elongin B and Elongin C, components of Cullin E3 ubiquitin ligase complexes. This occurs via direct interaction of PRAME with Elongin C, and PRAME colocalises with Elongins in the Golgi after PAMP/IFNγ treatment. PRAME was also found to co-immunoprecipitate core histones, consistent with its partial localisation to the nucleus, and was found to bind directly to histone H3 in vitro. Thus, PRAME is upregulated by signalling pathways that are activated in response to infection/inflammation, and its product may have dual functions as a histone-binding protein, and in directing ubiquitylation of target proteins for processing in the Golgi.

A Type VI secretion system encoding locus is required for Bordetella bronchiseptica immunomodulation and persistence in vivo

Type VI Secretion Systems (T6SSs) have been identified in numerous Gram-negative pathogens, but the lack of a natural host infection model has limited analysis of T6SS contributions to infection and pathogenesis. Here, we describe disruption of a gene within locus encoding a putative T6SS in Bordetella bronchiseptica strain RB50, a respiratory pathogen that circulates in a broad range of mammals, including humans, domestic animals, and mice. The 26 gene locus encoding the B. bronchiseptica T6SS contains apparent orthologs to all known core genes and possesses thirteen novel genes. By generating an in frame deletion of clpV, which encodes a putative ATPase required for some T6SS-dependent protein secretion, we observe that ClpV contributes to in vitro macrophage cytotoxicity while inducing several eukaryotic proteins associated with apoptosis. Additionally, ClpV is required for induction of IL-1β, IL-6, IL-17, and IL-10 production in J774 macrophages infected with RB50. During infections in wild type mice, we determined that ClpV contributes to altered cytokine production, increased pathology, delayed lower respiratory tract clearance, and long term nasal cavity persistence. Together, these results reveal a natural host infection system in which to interrogate T6SS contributions to immunomodulation and pathogenesis.

Thyroid hormone enhances nitric oxide-mediated bacterial clearance and promotes survival after meningococcal infection

Euthyroid sick syndrome characterized by reduced levels of thyroid hormones (THs) is observed in patients with meningococcal shock. It has been found that the level of THs reflects disease severity and is predictive for mortality. The present study was conducted to investigate the impact of THs on host defense during meningococcal infection. We found that supplementation of thyroxine to mice infected with Neisseria meningitidis enhanced bacterial clearance, attenuated the inflammatory responses and promoted survival. In vitro studies with macrophages revealed that THs enhanced bacteria-cell interaction and intracellular killing of meningococci by stimulating inducible nitric oxide synthase (iNos)-mediated NO production. TH treatment did not activate expression of TH receptors in macrophages. Instead, the observed TH-directed actions were mediated through nongenomic pathways involving the protein kinases PI3K and ERK1/2 and initiated at the membrane receptor integrin αvβ3. Inhibition of nongenomic TH signaling prevented iNos induction, NO production and subsequent intracellular bacterial killing by macrophages. These data demonstrate a beneficial role of THs in macrophage-mediated N. meningitidis clearance. TH replacement might be a novel option to control meningococcal septicemia.

Metabolic reprogramming: a cancer hallmark even warburg did not anticipate

Cancer metabolism has long been equated with aerobic glycolysis, seen by early biochemists as primitive and inefficient. Despite these early beliefs, the metabolic signatures of cancer cells are not passive responses to damaged mitochondria but result from oncogene-directed metabolic reprogramming required to support anabolic growth. Recent evidence suggests that metabolites themselves can be oncogenic by altering cell signaling and blocking cellular differentiation. No longer can cancer-associated alterations in metabolism be viewed as an indirect response to cell proliferation and survival signals. We contend that altered metabolism has attained the status of a core hallmark of cancer.

Defining the role of TRIP6 in cell physiology and cancer

Integrating signals from the ECM (extracellular matrix) via the cell surface into the nucleus is an essential feature of multicellular life and often malfunctions in cancer. To date many signal transducers known as shuttle proteins have been identified that act as both: a cytoskeletal and a signalling protein. Here, we highlight the interesting member of the Zyxin family TRIP6 [thyroid receptor interactor protein 6; also designated ZRP-1 (zyxin-related protein 1)] and review current literature to define its role in cell physiology and cancer. TRIP6 is a versatile scaffolding protein at FAs (focal adhesions) involved in cytoskeletal organization, coordinated cell migration and tissue invasion. Via its LIM and TDC domains TRIP6 interacts with different components of the LPA (lysophosphatidic acid), NF-κB (nuclear factor κB), glucocorticoid and AMPK (AMP-activated protein kinase) signalling pathway and thereby modulates their activity. Within the nucleus TRIP6 acts as a transcriptional cofactor regulating the transcriptional responses of these pathways. Moreover, intranuclear TRIP6 associates with proteins ensuring telomere protection and hence may contribute to genome stability. Accordingly, TRIP6 is engaged in key cellular processes such as cell proliferation, differentiation and survival. These diverse functions of TRIP6 are found to be dysregulated in various cancers and may have pleiotropic roles in tumour initiation, tumour growth and metastasis, which turn TRIP6 into an attractive candidate for cancer diagnosis and targeted therapy.

Characterization of an Opa interacting protein 5 involved in lung and esophageal carcinogenesis

To identify potential molecular targets for diagnosis, treatment and/or prevention of lung and esophageal carcinomas, we screened for genes that were overexpressed in tumors through gene expression analyses of 120 lung cancers and 19 esophageal squamous-cell carcinomas using a cDNA microarray consisting of 27,648 cDNA or expressed sequence tags. In this process, we identified a gene, Opa interacting protein 5 (OIP5), to be highly transactivated in the majority of lung and esophageal cancers. Immunohistochemical staining using 336 archived non-small cell lung cancers and 305 esophageal squamous-cell carcinomas specimens demonstrated that OIP5 expression was significantly associated with poor prognosis of lung and esophageal cancer patients (P = 0.0053 and 0.0168, respectively), and multivariate analysis confirmed its independent prognostic value for non-small cell lung cancers (P = 0.0112). Suppression of OIP5 expression with siRNA effectively suppressed the growth of cancer cells, whereas the exogenous expression of OIP5 enhanced the growth of cancer cells. In addition, OIP5 protein is likely to be stabilized through its interaction with Raf1. OIP5 is a promising target for developing new prognostic biomarkers and anti-cancer drugs.

The effect of selenium enrichment on baker's yeast proteome

The use of regular yeast (RY) and selenium-enriched yeast (SEY) as dietary supplement is of interest because the Nutritional Prevention of Cancer (NPC) trial revealed that SEY but not RY decreased the incidence of prostate cancer (PC). Using two-dimensional difference in gel electrophoresis (2D-DIGE)-tandem mass spectrometry (MS/MS) approach, we performed proteomic analysis of RY and SEY to identify proteins that are differentially expressed as a result of selenium enrichment. 2D-DIGE revealed 96 candidate protein spots that were differentially expressed (p≤0.05) between SEY and RY. The 96 spots were selected, sequenced by LC/MS/MS and 37 proteins were unequivocally identified. The 37 identified proteins were verified with ProteinProphet software and mapped to existing Gene Ontology categories. Furthermore, the expression profile of 5 of the proteins with validated or putative roles in the carcinogenesis process, and for which antibodies against human forms of the proteins are available commercially was verified by western analysis. This study provides evidence for the first time that SEY contains higher levels of Pyruvate Kinase, HSP70, and Elongation factor 2 and lower levels of Eukaryotic Translation Initiation Factor 5A-2 and Triosephosphate Isomerase than those found in RY.

TRIP6: an adaptor protein that regulates cell motility, antiapoptotic signaling and transcriptional activity

Thyroid hormone receptor interacting protein 6 (TRIP6), also known as zyxin-related protein-1 (ZRP-1), is an adaptor protein that belongs to the zyxin family of LIM proteins. TRIP6 is primarily localized in the cytosol or focal adhesion plaques, and may associate with the actin cytoskeleton. Additionally, it is capable of shuttling to the nucleus to serve as a transcriptional coregulator. Structural and functional analyses have revealed that through multidomain-mediated protein-protein interactions, TRIP6 serves as a platform for the recruitment of a wide variety of signaling molecules involved in diverse cellular responses, such as actin cytoskeletal reorganization, cell adhesion and migration, antiapoptotic signaling, osteoclast sealing zone formation and transcriptional control. Although the physiological functions of TRIP6 remain largely unknown, it has been implicated in cancer progression and telomere protection. Together, these studies suggest that TRIP6 plays multifunctional roles in different cellular responses, and thus may represent a novel target for therapeutic intervention.

Human pyruvate kinase M2: a multifunctional protein

Glycolysis, a central metabolic pathway, harbors evolutionary conserved enzymes that modulate and potentially shift the cellular metabolism on requirement. Pyruvate kinase, which catalyzes the last but rate-limiting step of glycolysis, is expressed in four isozymic forms, depending on the tissue requirement. M2 isoform (PKM2) is exclusively expressed in embryonic and adult dividing/tumor cells. This tetrameric allosterically regulated isoform is intrinsically designed to downregulate its activity by subunit dissociation (into dimer), which results in partial inhibition of glycolysis at the last step. This accumulates all upstream glycolytic intermediates as an anabolic feed for synthesis of lipids and nucleic acids, whereas reassociation of PKM2 into active tetramer replenishes the normal catabolism as a feedback after cell division. In addition, involvement of this enzyme in a variety of pathways, protein-protein interactions, and nuclear transport suggests its potential to perform multiple nonglycolytic functions with diverse implications, although multidimensional role of this protein is as yet not fully explored. This review aims to provide an overview of the involvement of PKM2 in various physiological pathways with possible functional implications.

OIP5 is a highly expressed potential therapeutic target for colorectal and gastric cancers

Previously, we reported that overexpression of Opa (Neisseria gonorrhoeae opacity-associated)-interacting protein 5 (OIP5) caused multi-septa formation and growth defects, both of which are considered cancer-related phenotypes. To evaluate OIP5 as a possible cancer therapeutic target, we examined its expression level in 66 colorectal cancer patients. OIP5 was upregulated about 3.7-fold in tumors and over 2-fold in 58 out of 66 colorectal cancer patients. Knockdown of OIP5 expression by small interfering RNA specific to OIP5 (siOIP5) resulted in growth inhibition of colorectal and gastric cancer cell lines. Growth inhibition of SNU638 by siOIP5 caused an increase in sub-G1 DNA content, as measured by flow cytometry, as well as an apoptotic gene expression profile. These results indicate that knockdown of OIP5 may induce apoptosis in cancer cells. Therefore, we suggest that OIP5 might be a potential cancer therapeutic target, although the mechanisms of OIP5-induced carcinogenesis should be elucidated.

Leucine-rich repeat protein PRAME: expression, potential functions and clinical implications for leukaemia

PRAME/MAPE/OIP4 is a germinal tissue-specific gene that is also expressed at high levels in haematological malignancies and solid tumours. The physiological functions of PRAME in normal and tumour cells are unknown, although a role in the regulation of retinoic acid signalling has been proposed. Sequence homology and structural predictions suggest that PRAME is related to the leucine-rich repeat (LRR) family of proteins, which have diverse functions. Here we review the current knowledge of the structure/function of PRAME and its relevance in leukaemia.

Neisseria meningitidis Opc invasin binds to the cytoskeletal protein alpha-actinin

Neisseria meningitidis Opc protein is an effective invasin for human endothelial cells. We have investigated novel human endothelial receptors targeted by Opc and observed that Opc-expressing bacteria interacted with a 100 kDa protein in whole-cell lysates of human endothelial and epithelial cells. The identity of the protein was established as alpha-actinin by mass spectrometry. Opc expression was essential for the recognition of alpha-actinin whether provided in a purified form or in cell extracts. The interaction of the two proteins did not involve intermediate molecules. As there was no demonstrable expression of alpha-actinin on the surfaces of any of the eight cell lines studied, the likelihood of the interactions after meningococcal internalization was examined. Confocal imaging demonstrated considerable colocalization of N. meningitidis with alpha-actinin especially after a prolonged period of internalization. This may imply that bacteria and alpha-actinin initially occur in separate compartments and co-compartmentalization occurs progressively over the 8 h infection period used. In conclusion, these studies have identified a novel and an intracellular target for the N. meningitidis Opc invasin. Since alpha-actinin is a modulator of a variety of signalling pathways and of cytoskeletal functions, its targeting by Opc may enable bacteria to survive/translocate across endothelial barriers.

Reverse transcriptase-PCR differential display analysis of meningococcal transcripts during infection of human cells: up-regulation of priA and its role in intracellular replication

BACKGROUND

In vitro studies with cell line infection models are beginning to disclose the strategies that Neisseria meningitidis uses to survive and multiply inside the environment of the infected host cell. The goal of this study was to identify novel virulence determinants that are involved in this process using an in vitro infection system.

RESULTS

By using reverse transcriptase-PCR differential display we have identified a set of meningococcal genes significantly up-regulated during residence of the bacteria in infected HeLa cells including genes involved in L-glutamate transport (gltT operon), citrate metabolism (gltA), disulfide bond formation (dsbC), two-partner secretion (hrpA-hrpB), capsulation (lipA), and DNA replication/repair (priA). The role of PriA, a protein that in Escherichia coli plays a central role in replication restart of collapsed or arrested DNA replication forks, has been investigated. priA inactivation resulted in a number of growth phenotypes that were fully complemented by supplying a functional copy of priA. The priA-defective mutant exhibited reduced viability during late logarithmic growth phase. This defect was more severe when it was incubated under oxygen-limiting conditions using nitrite as terminal electron acceptors in anaerobic respiration. When compared to wild type it was more sensitive to hydrogen peroxide and the nitric oxide generator sodium nitroprusside. The priA-defective strain was not affected in its ability to invade HeLa cells, but, noticeably, exhibited severely impaired intracellular replication and, at variance with wild type and complemented strains, it co-localized with lysosomal associated membrane protein 1.

CONCLUSION

In conclusion, our study i.) demonstrates the efficacy of the experimental strategy that we describe for discovering novel virulence determinants of N. meningitidis and ii.) provides evidence for a role of priA in preventing both oxidative and nitrosative injury, and in intracellular meningococcal replication.

Quantification of bacterial internalization by host cells using a beta-lactamase reporter strain: Neisseria gonorrhoeae invasion into cervical epithelial cells requires bacterial viability

Neisseria gonorrhoeae can invade into cervical epithelial cells to overcome this host defense barrier. We developed a beta-lactamase reporter system that allowed us to quantify at the single cell level if a host cell internalized a viable or nonviable microorganism. We autodisplayed beta-lactamase on the surface of FA1090 [FA1090Phi(bla-iga')] and demonstrated by confocal fluorescence microscopy and flow cytometry that FA1090Phi(bla-iga') cleaved the beta-lactamase substrate CCF2-AM loaded into host cells only when gonococci were internalized by these host cells. While FA1090Phi(bla-iga') adhered to almost all ME180 cells, viable N. gonorrhoeae were internalized by only a subset of cells during infection. Nonviable gonococci adhered to, but were not internalized by ME180 cells, and failed to recruit F-actin to sites of adherent bacteria. Overall, we show that epithelial cell invasion is a dynamic process that requires viable N. gonorrhoeae. We demonstrate the advantages of the beta-lactamase reporter system over the gentamicin protection assay in quantifying bacterial invasion. The reporter system that we have developed can be adapted to studying the internalization of any bacterial species into any host cell.

ZRP-1 controls Rho GTPase-mediated actin reorganization by localizing at cell-matrix and cell-cell adhesions

Focal adhesion protein ZRP-1/TRIP6 has been implicated in actin reorganization and cell motility. The role of ZRP-1, however, remained obscure because previously reported data are often conflicting one another. In the present study, we examined roles of ZRP-1 in HeLa cells. ZRP-1 is localized to the cell-cell contact sites as well as to cell-matrix contact sites in HeLa cells. RNA-interference-mediated depletion of ZRP-1 from HeLa cells revealed that ZRP-1 is essential not only for the formation of stress fibers and assembly of mature focal adhesions, but also for the actin reorganization at cell-cell contact sites and for correct cell-cell adhesion and, thus, for collective cell migration. Impairment of focal adhesions and stress fibers caused by ZRP-1 depletion has been associated with reduced tyrosine phosphorylation of FAK. However, maturation of focal adhesions could not be recovered by expression of active FAK. Interestingly, stress fibers in ZRP-1-depleted cells were ameliorated by exogenous expression of RhoA. We also found that total Rac1 activity is elevated in ZRP-1-depleted cells, resulting in abnormal burst of actin polymerization and dynamic membrane protrusions. Taken together, we conclude that that ZRP-1 plays a crucial role in coupling the cell-matrix/cell-cell-contact signals with Rho GTPase-mediated actin remodeling by localizing at cell-matrix and cell-cell contact sites.

LAP2alpha-binding protein LINT-25 is a novel chromatin-associated protein involved in cell cycle exit

Lamina-associated polypeptide 2alpha (LAP2alpha) is a nuclear protein dynamically associating with chromatin during the cell cycle. In addition, LAP2alpha interacts with A-type lamins and retinoblastoma protein and regulates cell cycle progression via the E2F-Rb pathway. Using yeast two-hybrid analysis and three independent in vitro binding assays we identified a new LAP2alpha interaction partner of hitherto unknown functions, which we termed LINT-25. LINT-25 protein levels were upregulated during G1 phase in proliferating cells and upon cell cycle exit in quiescence, senescence and differentiation. Upon cell cycle exit LINT-25 accumulated in heterochromatin foci, and LAP2alpha protein levels were downregulated by proteasomal degradation. Although LAP2alpha was not required for the upregulation and reorganization of LINT-25 during cell cycle exit, transient expression of LINT-25 in proliferating cells caused loss of LAP2alpha and subsequent cell death. Our data show a role of LINT-25 and LAP2alpha during cell cycle exit, in which LINT-25 acts upstream of LAP2alpha.

Supervillin modulation of focal adhesions involving TRIP6/ZRP-1

Cell-substrate contacts, called focal adhesions (FAs), are dynamic in rapidly moving cells. We show that supervillin (SV)--a peripheral membrane protein that binds myosin II and F-actin in such cells--negatively regulates stress fibers, FAs, and cell-substrate adhesion. The major FA regulatory sequence within SV (SV342-571) binds to the LIM domains of two proteins in the zyxin family, thyroid receptor-interacting protein 6 (TRIP6) and lipoma-preferred partner (LPP), but not to zyxin itself. SV and TRIP6 colocalize within large FAs, where TRIP6 may help recruit SV. RNAi-mediated decreases in either protein increase cell adhesion to fibronectin. TRIP6 partially rescues SV effects on stress fibers and FAs, apparently by mislocating SV away from FAs. Thus, SV interactions with TRIP6 at FAs promote loss of FA structure and function. SV and TRIP6 binding partners suggest several specific mechanisms through which the SV-TRIP6 interaction may regulate FA maturation and/or disassembly.

Identification of a meningococcal L-glutamate ABC transporter operon essential for growth in low-sodium environments

GdhR is a meningococcal transcriptional regulator that was previously shown to positively control the expression of gdhA, encoding the NADP-specific L-glutamate dehydrogenase (NADP-GDH), in response to the growth phase and/or to the carbon source. In this study we used reverse transcriptase-PCR-differential display (to identify additional GdhR-regulated genes. The results indicated that GdhR, in addition to NADP-GDH, controls the expression of a number of genes involved in glucose catabolism by the Entner-Doudoroff pathway and in l-glutamate import by an unknown ABC transport system. The genes encoding the putative periplasmic substrate-binding protein (NMB1963) and the permease (NMB1965) of the ABC transporter were genetically inactivated. Uptake experiments demonstrated an impairment of L-glutamate import in the NMB1965-defective mutant in the absence or in the presence of a low sodium ion concentration. In contrast, at a sodium ion concentration above 60 mM, the uptake defect disappeared, possibly because the activity of a sodium-driven secondary transporter became predominant. Indeed, the NMB1965-defective mutant was unable to grow at a low sodium ion concentration (<20 mM) in a chemically defined medium containing L-glutamate and four other amino acids that supported meningococcal growth, but it grew when the sodium ion concentration was raised to higher values (>60 mM). The same growth phenotype was observed in the NMB1963-defective mutant. Cell invasion and intracellular persistence assays and expression data during cell invasion provided evidence that the l-glutamate ABC transporter, tentatively named GltT, was critical for meningococcal adaptation in the low-sodium intracellular environment.