Differential Regulation of Karyopherin α 2 Expression by TGF-β1 and IFN-γ in Normal Human Epidermal Keratinocytes: Evident Contribution of KPNA2 for Nuclear Translocation of IRF-1

Silencing of tropomodulin 1 inhibits acute myeloid leukemia cell proliferation and tumor growth by elevating karyopherin alpha 2-mediated autophagy

Evidence shows that tropomodulin 1 (TMOD1) is a powerful diagnostic marker in the progression of several cancer types. However, the regulatory mechanism of TMOD1 in tumor progression is still unclear. Here, we showed that TMOD1 was highly expressed in acute myeloid leukemia (AML) specimens, and TMOD1-silencing inhibited cell proliferation by inducing autophagy in AML THP-1 and MOLM-13 cells. Mechanistically, the C-terminal region of TMOD1 directly bound to KPNA2, and TMOD1-overexpression promoted KPNA2 ubiquitylation and reduced KPNA2 levels. In contrast, TMOD1-silencing increased KPNA2 levels and facilitated the nuclear transfer of KPNA2, then subsequently induced autophagy and inhibited cell proliferation by increasing the nucleocytoplasmic transport of p53 and AMPK activation. KPNA2/p53 inhibitors attenuated autophagy induced by silencing TMOD1 in AML cells. Silencing TMOD1 also inhibited tumor growth by elevating KPNA2-mediated autophagy in nude mice bearing MOLM-13 xenografts. Collectively, our data demonstrated that TMOD1 could be a novel therapeutic target for AML treatment.

Upping the ante: enhanced expression of interferon-antagonizing ORF6 and ORF9b proteins by SARS-CoV-2 variants of concern

SARS-CoV-2 exhibits a remarkable capability to subvert the host antiviral innate immune system. This adeptness is orchestrated by viral proteins, which initially attempt to obstruct the activation of the antiviral immune program and then act as a fail-safe mechanism to mitigate the downstream effects of the activated immune response. This dual strategy leads to delayed expression and enfeebled action of type-I and -III interferons at the infection site, enabling the virus to replicate extensively in the lungs and subsequently disseminate to other organs. Throughout the course of the COVID-19 pandemic, SARS-CoV-2 has undergone evolution, giving rise to several variants of concern, some with exceedingly higher transmission and virulence. These improved features have been linked, at least in part, to the heightened expression or activity of specific viral proteins involved in circumventing host defense mechanisms. In this review, we aim to provide a concise summary of two SARS-CoV-2 proteins, ORF6 and ORF9b, which provided selective advantage to certain variants, affecting their biology and pathogenesis.

Exploring casual effects and shared molecular mechanism between psoriasis and liver cancer through Mendelian randomization and comprehensive bioinformatic analyses

Psoriasis (Ps), a chronic inflammatory disease affecting approximately 2 % of the global population, has been associated with an increased risk of liver cancer in observational studies. However, their causal relationships as well as underlying shared molecular mechanisms between Ps and liver cancer remain unclear. Using bidirectional Mendelian randomization analysis, we revealed that a genetic predisposition to liver cancer increased the risk of Ps in European and East Asian populations but not the other way around. Moreover, we analyzed three transcriptomic datasets of patients with Ps and liver cancer from open-source databases. Differentially expressed genes (DEGs) and disease-specific gene co-expression module analyses revealed that cell-cycle dysregulation was the shared mechanism of Ps and liver cancer. Moreover, we identified a rank-conservative gene signature shared between these two diseases, which demonstrated significance in diagnostic and prognostic predictions. These findings provided valuable insights into the interconnections between Ps and liver cancer, which may be helpful to guide therapeutic management.

Loss of the importin Kpna2 causes infertility in male mice by disrupting the translocation of testis-specific transcription factors

Karyopherins mediate the movement between the nucleus and cytoplasm of specific proteins in diverse cellular processes. Through a loss-of-function approach, we here examine the role of Karyopherin Subunit Alpha 2 (Kpna2) in spermatogenesis. Knockout male mice exhibited reduced body size and sperm motility, increased sperm abnormalities, and led to the dysregulation of testis gene expression and ultimately to infertility. Impaired mRNA expression mainly affected clusters of genes expressed in spermatids and spermatocytes. Downregulated genes included a set of genes that participate in cell adhesion and extracellular matrix (ECM) organization. We detected both the enrichment of some transcription factors that bind to regions around transcription start sites of downregulated genes and the impaired transport of specific factors to the nucleus of spermatid cells. We propose that Kpna2 is essential in the seminiferous tubules for promoting the translocation of testis-specific transcription factors that control the expression of genes related to ECM organization.

Nuclear import of IRF11 via the importin α/β pathway is essential for its antiviral activity

Interferon regulatory factor 11 (IRF11), an intriguing IRF member found only in fish species, has recently been shown to have antiviral properties that are dependent on its nuclear entry and DNA binding affinity. However, the mechanisms by which IRF11 enters the nucleus are unknown. In the present study, we found orthologs of IRF11 in lamprey and lancelet species by combining positional, phylogenetic and structural comparison data, showing that this gene has an ancient origin. The IRF11 gene (AjIRF11) from the Japanese eel, Anguilla japonica, was subsequently characterized, and it was found that AjIRF11 has antiviral activities against spring viremia of carp virus (SVCV), which are accomplished by regulating the production of type I IFN and IFN-stimulated genes. In addition to its known DNA binding residues in the α3 helix, two residues in Loop 1, His40 and Trp46, are also involved in DNA binding and activation of the IFN promoter. Using immunofluorescence microscopy and site-directed mutagenesis analysis, we confirmed that full nuclear localization of AjIRF11 requires the bipartite nuclear localization sequence (NLS) spanning residues 75 to 101, as well as the monopartite NLS situated between residues 119 and 122. Coimmunoprecipitation assays confirmed that AjIRF11 interacts with importin α via its NLSs and can also bind to importin β directly, implying that IRF11 can be imported to the nucleus by one or more transport receptors.

Bayesian model and selection signature analyses reveal risk factors for canine atopic dermatitis

Canine atopic dermatitis is an inflammatory skin disease with clinical similarities to human atopic dermatitis. Several dog breeds are at increased risk for developing this disease but previous genetic associations are poorly defined. To identify additional genetic risk factors for canine atopic dermatitis, we here apply a Bayesian mixture model adapted for mapping complex traits and a cross-population extended haplotype test to search for disease-associated loci and selective sweeps in four dog breeds at risk for atopic dermatitis. We define 15 associated loci and eight candidate regions under selection by comparing cases with controls. One associated locus is syntenic to the major genetic risk locus (Filaggrin locus) in human atopic dermatitis. One selection signal in common type Labrador retriever cases positions across the TBC1D1 gene (body weight) and one signal of selection in working type German shepherd controls overlaps the LRP1B gene (brain), near the KYNU gene (psoriasis). In conclusion, we identify candidate genes, including genes belonging to the same biological pathways across multiple loci, with potential relevance to the pathogenesis of canine atopic dermatitis. The results show genetic similarities between dog and human atopic dermatitis, and future across-species genetic comparisons are hereby further motivated.

Participation of interferons in psoriatic inflammation

Interferons are multifunctional cytokines not expressed in the skin under normal physiological conditions. However, they are overexpressed in serum and skin lesions of patients with psoriasis and play an important role in the pathogenesis of the disease. Interferons act directly on skin resident cells and recruit and modulate inflammatory cells, thereby exacerbating psoriatic inflammation. They upregulate the expression of relevant cytokines and chemokines, facilitate excessive proliferation of keratinocytes, and enhance the formation of poorly differentiated dermal microvessels. In this review, we summarized the pathogenic effect of interferons on psoriasis and also discussed the therapeutic strategies targeting interferons.

SARS-CoV-2 inhibits induction of the MHC class I pathway by targeting the STAT1-IRF1-NLRC5 axis

The MHC class I-mediated antigen presentation pathway plays a critical role in antiviral immunity. Here we show that the MHC class I pathway is targeted by SARS-CoV-2. Analysis of the gene expression profile from COVID-19 patients as well as SARS-CoV-2 infected epithelial cell lines reveals that the induction of the MHC class I pathway is inhibited by SARS-CoV-2 infection. We show that NLRC5, an MHC class I transactivator, is suppressed both transcriptionally and functionally by the SARS-CoV-2 ORF6 protein, providing a mechanistic link. SARS-CoV-2 ORF6 hampers type II interferon-mediated STAT1 signaling, resulting in diminished upregulation of NLRC5 and IRF1 gene expression. Moreover, SARS-CoV-2 ORF6 inhibits NLRC5 function via blocking karyopherin complex-dependent nuclear import of NLRC5. Collectively, our study uncovers an immune evasion mechanism of SARS-CoV-2 that targets the function of key MHC class I transcriptional regulators, STAT1-IRF1-NLRC5.

The presentation of viral antigens to T cells via the MHC molecules is a critical component of the host response to viral infection. Here the authors suggest SARS-CoV-2 possesses the immune evasion strategy against the MHC class I pathway by targeting key transcriptional regulators.

Oncogenic role of karyopherin α2 (KPNA2) in human tumors: A pan-cancer analysis

BACKGROUND

KPNA2, a nuclear export protein that plays an important role in tumorigenesis, is an emerging hotspot target in oncology. Despite increasing supporting evidence of its importance, no pan-cancer analysis, across multiple databases, is available for in-depth data mining of the gene.

METHODS

Tumor data from both The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were explored to investigate the potential oncogenic roles of KPNA2. Diverse analytical methods were used to gain a full-scale understanding of KPNA2: gene expression, survival situations, genetic mutations, DNA methylation, sites of protein phosphorylation, immunocyte infiltration, and correlative cellular pathways.

RESULTS

KPNA2 is highly expressed in many cancers, and different correlations exist between KPNA2 expression and prognosis of cancer patients. cBioPortal reported that a nonsense mutation of R285* was considered to be the primary tumorigenic genetic alteration to KPNA2 and was found in cases of LUSC, STAD, and CESC. Enhanced phosphorylation of S62 was found in several cancers and the level of infiltration of cancer-associated fibroblasts was found to be linearly correlated with KPNA2 expression levels in ACC, BRCA, MESO, TGCT, THCA, and THYM. Correlations between KPNA2 DNA methylation and the pathogenesis of various tumors in TCGA were further identified. KEGG and GO enrichment analysis identified cell cycle, microtubule binding, and tubulin binding functions for KPNA2.

CONCLUSION

This is the first pan-cancer analysis focusing on KPNA2. It provides a comprehensive understanding about the role of KPNA2 in tumorigenesis and highlights the potential targeted role of KPNA2 for cancer study.

KPNB1 Inhibitor Importazole Reduces Ionizing Radiation-Increased Cell Surface PD-L1 Expression by Modulating Expression and Nuclear Import of IRF1

Programmed death-ligand 1 (PD-L1) is an immune checkpoint molecule that negatively regulates anti-tumor immunity. Recent reports indicate that anti-cancer treatments, such as radiation therapy, increase PD-L1 expression on the surface of tumor cells. We previously reported that the nuclear transport receptor karyopherin-β1 (KPNB1) is involved in radiation-increased PD-L1 expression on head-and-neck squamous cell carcinoma cells. However, the mechanisms underlying KPNB1-mediated, radiation-increased PD-L1 expression remain unknown. Thus, the mechanisms of radiation-increased, KPNB1-mediated PD-L1 expression were investigated by focusing on the transcription factor interferon regulatory factor 1 (IRF1), which is reported to regulate PD-L1 expression. Western blot analysis showed that radiation increased IRF1 expression. In addition, flow cytometry showed that IRF1 knockdown decreased cell surface PD-L1 expression of irradiated cells but had a limited effect on non-irradiated cells. These findings suggest that the upregulation of IRF1 after irradiation is required for radiation-increased PD-L1 expression. Notably, immunofluorescence and western blot analyses revealed that KPNB1 inhibitor importazole not only diffused nuclear localization of IRF1 but also decreased IRF1 upregulation by irradiation, which attenuated radiation-increased PD-L1 expression. Taken together, these findings suggest that KPNB1 mediates radiation-increased cell surface PD-L1 expression through both upregulation and nuclear import of IRF1.

Karyopherin-β1 Regulates Radioresistance and Radiation-Increased Programmed Death-Ligand 1 Expression in Human Head and Neck Squamous Cell Carcinoma Cell Lines

Nuclear transport receptors, such as karyopherin-β1 (KPNB1), play important roles in the nuclear-cytoplasmic transport of macromolecules. Recent evidence indicates the involvement of nuclear transport receptors in the progression of cancer, making these receptors promising targets for the treatment of cancer. Here, we investigated the anticancer effects of KPNB1 blockage or in combination with ionizing radiation on human head and neck squamous cell carcinoma (HNSCC). HNSCC cell line SAS and Ca9-22 cells were used in this study. Importazole, an inhibitor of KPNB1, or knockdown of KPNB1 by siRNA transfection were applied for the blockage of KPNB1 functions. The roles of KPNB1 on apoptosis induction and cell surface expression levels of programmed death-ligand 1 (PD-L1) in irradiated HNSCC cells were investigated. The major findings of this study are that (i) blockage of KPNB1 specifically enhanced the radiation-induced apoptosis and radiosensitivity of HNSCC cells; (ii) importazole elevated p53-upregulated modulator of apoptosis (PUMA) expression via blocking the nuclear import of SCC-specific oncogene ΔNp63 in HNSCC cells; and (iii) blockage of KPNB1 attenuated the upregulation of cell surface PD-L1 expression on irradiated HNSCC cells. Taken together, these results suggest that co-treatment with KPNB1 blockage and ionizing radiation is a promising strategy for the treatment of HNSCC.

MicroRNA-302 Cluster Downregulates Enterovirus 71-Induced Innate Immune Response by Targeting KPNA2

Enterovirus 71 (EV71) induces significantly elevated levels of cytokines and chemokines, leading to local or systemic inflammation and severe complications. As shown in our previous study, microRNA (miR) 302c regulates influenza A virus-induced IFN expression by targeting NF-κB-inducing kinase. However, little is known about the role of the miR-302 cluster in EV71-mediated proinflammatory responses. In this study, we found that the miR-302 cluster controls EV71-induced cytokine expression. Further studies demonstrated that karyopherin α2 (KPNA2) is a direct target of the miR-302 cluster. Interestingly, we also found that EV71 infection upregulates KPNA2 expression by downregulating miR-302 cluster expression. Upon investigating the mechanisms behind this event, we found that KPNA2 intracellularly associates with JNK1/JNK2 and p38, leading to translocation of those transcription factors from the cytosol into the nucleus. In EV71-infected patients, miR-302 cluster expression was downregulated and KPNA2 expression was upregulated compared with controls, and their expression levels were closely correlated. Taken together, our work establishes a link between the miR-302/ KPNA2 axis and EV71-induced cytokine expression and represents a promising target for future antiviral therapy.

Overexpression of karyopherin-α2 in cholangiocarcinoma correlates with poor prognosis and gemcitabine sensitivity via nuclear translocation of DNA repair proteins

Cholangiocarcinoma is a highly malignant tumor, and the development of new therapeutic strategies is critical. Karyopherin-α2 (KPNA2) functions as an adaptor that mediates nucleocytoplasmic transport. Specifically, KPNA2 transports one of the important DNA repair machineries, the MRE11-RAD50-NBS1 (MRN) complex, to the nucleus. In this study, we clarified the significance of KPNA2 in cholangiocarcinoma. KPNA2 expression evaluated by immunohistochemical analysis was common in malignant tissue but rare in adjacent noncancerous tissues. KPNA2 overexpression was significantly correlated with poor prognosis and was an independent prognostic factor after surgery. In patients with cholangiocarcinoma who received gemcitabine after surgery, KPNA2 overexpression tended to be a prognostic indicator of poor overall survival. In KPNA2-depleted cholangiocarcinoma cells, proliferation was significantly decreased and gemcitabine sensitivity was enhanced in vitro and in vivo. Expression of KPNA2 and the MRN complex displayed colocalization in the nucleus. In addition, nuclear localization of the MRN complex was regulated by KPNA2 in vitro. These results suggest that KPNA2 expression may be a useful prognostic and predictive marker of gemcitabine sensitivity and survival. The regulation of KPNA2 expression may be a new therapeutic strategy for cholangiocarcinoma.

Karyopherin alpha 2 expression is a novel diagnostic and prognostic factor for colorectal cancer

Colorectal cancer (CRC) is the fourth most common cancer and the second leading cause of cancer-associated mortality in Western countries. CRC treatment is dependent on the preoperative and postoperative condition of patients. At present, the prognostic value of conventional parameters for the estimation of patient prognosis is limited. The aim of the present study was to investigate the expression of karyopherin α2 (KPNA2) in cancerous and healthy colon tissues and to evaluate the prognostic factors for patients with primary CRC. KPNA2 expression in CRC and paired normal tissues was analyzed by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, serum KPNA2 expression was evaluated by enzyme-linked immunosorbent assay. Subsequently, the association between KPNA2 expression in CRC tissues and patient clinicopathological features was analyzed. Kaplan-Meier analysis was utilized to investigate the prognostic value of KPNA2 expression on overall survival rates following radical surgery for the treatment of CRC. Immunohistochemistry and RT-qPCR revealed that KPNA2 expression was significantly increased in CRC tissues compared with paired normal tissues. Serum KPNA2 expression was significantly increased in CRC patients compared with healthy individuals. Furthermore, KPNA2 expression was observed to positively correlate with Tumor-Node-Metastasis stage, lymph node involvement, tumor differentiation, infiltration depth, lymphovascular invasion and perineural invasion, which are factors known to affect the prognosis of CRC patients following surgery. In addition, increased KPNA2 expression was associated with decreased overall survival and disease-free survival rates. Patients not suited for surveillance regimens may be identified at initial biopsy test with a positive KPNA2 immunohistochemistry. Increased serum expression of KPNA2 may be utilized as a diagnostic factor for patients with CRC. High nuclear KPNA2 expression may serve as a novel predictor of survival following radical colorectal surgery in CRC patients. The results of the present study may improve individualized risk stratification, leading to the optimization of therapies for CRC patients.

MicroRNA-567 dysregulation contributes to carcinogenesis of breast cancer, targeting tumor cell proliferation, and migration

PURPOSE

We demonstrated that Hsa-miR-567 expression is significantly downregulated in poor prognosis breast cancer, compared to better prognosis breast cancer, having a role in the control of cell proliferation and migration by regulating KPNA4 gene.

METHODS AND RESULTS

In this study, based on our previously published in silico results, we proved both in vitro (cell line studies) and ex vivo (clinical studies), that Hsa-miR-567 expression is significantly downregulated in breast cancer with poor prognosis when compared to breast cancer with better prognosis. More intriguingly, we demonstrated that the ectopic expression of Hsa-miR-567 in poor prognosis breast cancer cell line strongly inhibits in vitro cell proliferation and migration. Furthermore, we showed in vivo that breast cancer cells, stably expressing Hsa-miR-567, xenografted in mouse, reduce tumor growth ability. Consistently, we found that karyopherin 4 (KPNA4), predicted target gene of Hsa-miR-567 as identified by our in silico analysis, is upregulated in highly aggressive MDA-MB-231 breast cancer cell line and patient tissues with poor prognosis with respect to good prognosis.

CONCLUSIONS

Our results suggest a potential role of Hsa-miR-567 as a novel prognostic biomarker for BC and as regulator of KPNA4.

Molecular changes in skin pigmented lesions of the coral trout Plectropomus leopardus

A high prevalence of skin pigmented lesions of 15% was recently reported in coral trout Plectropomus leopardus, a commercially important marine fish, inhabiting the Great Barrier Reef. Herein, fish were sampled at two offshore sites, characterised by high and low lesion prevalence. A transcriptomic approach using the suppressive subtractive hybridisation (SSH) method was used to analyse the differentially expressed genes between lesion and normal skin samples. Transcriptional changes of 14 genes were observed in lesion samples relative to normal skin samples. These targeted genes encoded for specific proteins which are involved in general cell function but also in different stages disrupted during the tumourigenesis process of other organisms, such as cell cycling, cell proliferation, skeletal organisation and cell migration. The results highlight transcripts that are associated with the lesion occurrence, contributing to a better understanding of the molecular aetiology of this coral trout skin disease.

Importins and exportins as therapeutic targets in cancer

The nuclear transport proteins, importins and exportins (karyopherin-β proteins), may play an important role in cancer by transporting key mediators of oncogenesis across the nuclear membrane in cancer cells. During nucleocytoplasmic transport of tumor suppressor proteins and cell cycle regulators during the processing of these proteins, aberrant cellular growth signaling and inactivation of apoptosis can occur, both critical to growth and development of tumors. Karyopherin-β proteins bind to these cargo proteins and RanGTP for active transport across the nuclear membrane through the nuclear pore complex. Importins and exportins are overexpressed in multiple tumors including melanoma, pancreatic, breast, colon, gastric, prostate, esophageal, lung cancer, and lymphomas. Furthermore, some of the karyopherin-β proteins such as exportin-1 have been implicated in drug resistance in cancer. Importin and exportin inhibitors are being considered as therapeutic targets against cancer and have shown preclinical anticancer activity. Moreover, synergistic activity has been observed with various chemotherapeutic and targeted agents. However, clinical development of the exportin-1 inhibitor leptomycin B was stopped due to adverse events, including vomiting, anorexia, and dehydration. Selinexor, a selective nuclear export inhibitor, is being tested in multiple clinical trials both as a single agent and in combination with chemotherapy. Selinexor has demonstrated clinical activity in multiple cancers, especially acute myelogenous leukemia and multiple myeloma. The roles of other importin and exportin inhibitors still need to be investigated clinically. Targeting the key mediators of nucleocytoplasmic transport in cancer cells represents a novel strategy in cancer intervention with the potential to significantly affect outcomes.

Karyopherin Alpha 1 Regulates Satellite Cell Proliferation and Survival by Modulating Nuclear Import

Satellite cells are stem cells with an essential role in skeletal muscle repair. Precise regulation of gene expression is critical for proper satellite cell quiescence, proliferation, differentiation and self-renewal. Nuclear proteins required for gene expression are dependent on the nucleocytoplasmic transport machinery to access to nucleus, however little is known about regulation of nuclear transport in satellite cells. The best characterized nuclear import pathway is classical nuclear import which depends on a classical nuclear localization signal (cNLS) in a cargo protein and the heterodimeric import receptors, karyopherin alpha (KPNA) and beta (KPNB). Multiple KPNA1 paralogs exist and can differ in importing specific cNLS proteins required for cell differentiation and function. We show that transcripts for six Kpna paralogs underwent distinct changes in mouse satellite cells during muscle regeneration accompanied by changes in cNLS proteins in nuclei. Depletion of KPNA1, the most dramatically altered KPNA, caused satellite cells in uninjured muscle to prematurely activate, proliferate and undergo apoptosis leading to satellite cell exhaustion with age. Increased proliferation of satellite cells led to enhanced muscle regeneration at early stages of regeneration. In addition, we observed impaired nuclear localization of two key KPNA1 cargo proteins: p27, a cyclin-dependent kinase inhibitor associated with cell cycle control and lymphoid enhancer factor 1, a critical cotranscription factor for β-catenin. These results indicate that regulated nuclear import of proteins by KPNA1 is critical for satellite cell proliferation and survival and establish classical nuclear import as a novel regulatory mechanism for controlling satellite cell fate. Stem Cells 2016;34:2784-2797.

Diversification of importin-α isoforms in cellular trafficking and disease states

The human genome encodes seven isoforms of importin α which are grouped into three subfamilies known as α1, α2 and α3. All isoforms share a fundamentally conserved architecture that consists of an N-terminal, autoinhibitory, importin-β-binding (IBB) domain and a C-terminal Arm (Armadillo)-core that associates with nuclear localization signal (NLS) cargoes. Despite striking similarity in amino acid sequence and 3D structure, importin-α isoforms display remarkable substrate specificity in vivo. In the present review, we look at key differences among importin-α isoforms and provide a comprehensive inventory of known viral and cellular cargoes that have been shown to associate preferentially with specific isoforms. We illustrate how the diversification of the adaptor importin α into seven isoforms expands the dynamic range and regulatory control of nucleocytoplasmic transport, offering unexpected opportunities for pharmacological intervention. The emerging view of importin α is that of a key signalling molecule, with isoforms that confer preferential nuclear entry and spatiotemporal specificity on viral and cellular cargoes directly linked to human diseases.

Restricted expression of karyopherin alpha mRNA in the sea urchin suggests a role in neurogenesis

Karyopherin alpha (KAP-α) proteins are critical for the transport of many molecules into the nucleus. In this study, we identified three members of the KAP-α family in the sea urchin Lytechinus variegatus and described the developmental expression of these proteins. Although many importins are assumed to have ubiquitous expression, we found that all three genes were differentially expressed. Both LvKPNA1/5/6 and LvKPNA3/4 accumulated at high levels during cleavage, exhibiting cyclic expression as cells divided. By the blastula and gastrula stages expression decreased, remaining highest in the vegetal plate and archenteron, and by the prism/pluteus stages expression was restricted to the oral surface and gut. Expression of a third KAP-α gene, LvKPNA2/7, was examined in embryos from the mesenchyme blastula to pluteus stages. LvKPNA2/7 mRNA is present in vegetal cells of the mesenchyme blastula and, during gastrulation, it is localized to the archenteron and appears in additional groups of ectodermal cells. Prism/pluteus stage embryos expressed LvKPNA2/7 in the gut and scattered distribution of transcripts in the ciliary band resembled expression patterns of neural cells. We hypothesize that LvKPNA2/7 maintains pluripotency in the neural precursors prior to activation of neural differentiation and believe that this study is an important first step in an effort to better understand the roles of importins during embryogenesis.

High nuclear karyopherin α 2 expression is a strong and independent predictor of biochemical recurrence in prostate cancer patients treated by radical prostatectomy

Increased levels of karyopherin α2 (KPNA2) expression have been described to be linked to poor prognosis in a variety of malignancies. This study was undertaken to evaluate the clinical impact of KPNA2 expression and its association with key genomic alterations in prostate cancers. A tissue microarray containing samples from 11 152 prostate cancers was analyzed for KPNA2 expression by immunohistochemistry. Results were compared with oncological follow-up data and genomic alterations such as TMPRSS2-ERG fusions and deletions of PTEN, 5q21, 6q15 or 3p13. KPNA2 expression was absent or weak in benign prostatic glands and was found to be in weak, moderate or strong intensities in 68.4% of 7964 interpretable prostate cancers. KPNA2 positivity was significantly linked to the presence of ERG rearrangement (P<0.0001). In ERG-negative and -positive prostate cancers, KPNA2 immunostaining was significantly associated with advanced pathological tumor stage (pT3b/pT4), high Gleason grade and early biochemical recurrence (P<0.0001 each). Multivariate analysis including all established prognostic criteria available after surgery revealed that the prognostic role of KPNA2 (P=0.001) was independent of high Gleason grade, advanced pathological tumor stage, high preoperative prostate-specific antigen level and positive surgical margin status (P<0.0001 each). The comparison of KPNA2 expression with deletions of PTEN, 5q21, 6q15 and 3p13 in ERG-positive and -negative cancers revealed a strong link to PTEN deletions in both subgroups (P<0.0001). In conclusion, the strong independent prognostic impact of KPNA2 expression raises the possibility that measurement of KPNA2 expression alone or in combination with other molecular parameters might possibly result in clinically useful information. The data also emphasize a critical role of the functionality of the nuclear import machinery for prostate cancer biology.

Karyopherin alpha2 is essential for rRNA transcription and protein synthesis in proliferative keratinocytes

Karyopherin proteins mediate nucleocytoplasmic trafficking and are critical for protein and RNA subcellular localization. Recent studies suggest KPNA2 expression is induced in tumor cells and is strongly associated with prognosis, although the precise roles and mechanisms of KPNA2 overexpression in proliferative disorders have not been defined. We found that KPNA2 expression is induced in various proliferative disorders of the skin such as psoriasis, Bowen’s disease, actinic keratosis, squamous cell carcinoma, Paget’s disease, Merkel cell carcinoma, and mycosis fungoides. siRNA-mediated KPNA suppression revealed that KPNA2 is essential for significant suppression of HaCaT proliferation under starvation conditions. Ribosomal RNA transcription and protein synthesis were suppressed by starvation combined with knockdown of KPNA (including KPNA2) expression. KPNA2 localized to the nucleolus and interacted with proteins associated with mRNA processing, ribonucleoprotein complex biogenesis, chromatin modification, and transcription, as demonstrated by tandem affinity purification and mass spectrometry. KPNA2 may be an important promoter of ribosomal RNA and protein synthesis in tumor cells.

Molecular profiling of multiple human cancers defines an inflammatory cancer-associated molecular pattern and uncovers KPNA2 as a uniform poor prognostic cancer marker

BACKGROUND

Immune evasion is one of the recognized hallmarks of cancer. Inflammatory responses to cancer can also contribute directly to oncogenesis. Since the immune system is hardwired to protect the host, there is a possibility that cancers, regardless of their histological origins, endow themselves with a common and shared inflammatory cancer-associated molecular pattern (iCAMP) to promote oncoinflammation. However, the definition of iCAMP has not been conceptually and experimentally investigated.

METHODS AND FINDINGS

Genome-wide cDNA expression data was analyzed for 221 normal and 324 cancer specimens from 7 cancer types: breast, prostate, lung, colon, gastric, oral and pancreatic. A total of 96 inflammatory genes with consistent dysregulation were identified, including 44 up-regulated and 52 down-regulated genes. Protein expression was confirmed by immunohistochemistry for some of these genes. The iCAMP contains proteins whose roles in cancer have been implicated and others which are yet to be appreciated. The clinical significance of many iCAMP genes was confirmed in multiple independent cohorts of colon and ovarian cancer patients. In both cases, better prognosis correlated strongly with high CXCL13 and low level of GREM1, LOX, TNFAIP6, CD36, and EDNRA. An "Inflammatory Gene Integrated Score" was further developed from the combination of 18 iCAMP genes in ovarian cancer, which predicted overall survival. Noticeably, as a selective nuclear import protein whose immuno-regulatory function just begins to emerge, karyopherin alpha 2 (KPNA2) is uniformly up-regulated across cancer types. For the first time, the cancer-specific up-regulation of KPNA2 and its clinical significance were verified by tissue microarray analysis in colon and head-neck cancers.

CONCLUSION

This work defines an inflammatory signature shared by seven epithelial cancer types and KPNA2 as a consistently up-regulated protein in cancer. Identification of iCAMP may not only serve as a novel biomarker for prognostication and individualized treatment of cancer, but also have significant biological implications.

The functional role of the novel biomarker karyopherin α 2 (KPNA2) in cancer

In recent years, Karyopherin α 2 (KPNA2) has emerged as a potential biomarker in multiple cancer forms. The aberrant high levels observed in cancer tissue have been associated with adverse patient characteristics, prompting the idea that KPNA2 plays a role in carcinogenesis. This notion is supported by studies in cancer cells, where KPNA2 deregulation has been demonstrated to affect malignant transformation. By virtue of its role in nucleocytoplasmic transport, KPNA2 is implicated in the translocation of several cancer-associated proteins. We provide an overview of the clinical studies that have established the biomarker potential of KPNA2 and describe its functional role with an emphasis on established associations with cancer.

Overexpression of karyopherin 2 in human ovarian malignant germ cell tumor correlates with poor prognosis

Background

The aim of this study was to identify a biomarker useful in the diagnosis and therapy of ovarian malignant germ cell tumor (OMGCT).

Methods

The karyopherin 2 (KPNA2) expression in OMGCT and normal ovarian tissue was determined by standard gene microarray assays, and further validated by a quantitative RT-PCR and immunohistochemistry. The correlation between KPNA2 expression in OMGCT and certain clinicopathological features were analyzed. Expression of SALL4, a stem cell marker, was also examined in comparison with KPNA2.

Results

KPNA2 was found to be over-expressed by approximately eight-fold in yolk sac tumors and immature teratomas compared to normal ovarian tissue by microarray assays. Overexpression was detected in yolk sac tumors, immature teratomas, dysgerminomas, embryonal carcinomas, mature teratomas with malignant transformation and mixed ovarian germ cell tumors at both the transcription and translation levels. A positive correlation between KPNA2 and SALL4 expression at both the transcription level (R = 0.5120, P = 0.0125), and the translation level (R = 0.6636, P<0.0001), was presented. Extensive expression of KPNA2 was positively associated with pathologic type, recurrence and uncontrolled, ascitic fluid presence, suboptimal cytoreductive surgery necessity, resistance/refraction to initial chemotherapy, HCG level and SALL4 level in OMGCT patients. KPNA2 was found to be an independent factor for 5-year disease-free survival (DFS) of OMGCT (P = 0.02). The 5-year overall survival (OS) and DFS rate for KPNA2-low expression patients (88% and 79%, n = 48) were significantly higher than the OS and DFS rate for KPNA2-high expression patients (69% and 57.1%, n = 42)(P = 0.0151, P = 0.0109, respectively). The 5-year OS and DFS rate for SALL4-low expression patients (84% and 74%, n = 62) was marginally significantly higher than the high expression patients (78.6% and 71.4%, n = 28)(P = 0.0519, P = 0.0647, respectively).

Conclusions

KPNA2 is a potential candidate molecular marker and important prognostic marker in OMGCT patients.

Quantitative proteomics reveals regulation of karyopherin subunit alpha-2 (KPNA2) and its potential novel cargo proteins in nonsmall cell lung cancer

The process of nucleocytoplasmic shuttling is mediated by karyopherins. Dysregulated expression of karyopherins may trigger oncogenesis through aberrant distribution of cargo proteins. Karyopherin subunit alpha-2 (KPNA2) was previously identified as a potential biomarker for nonsmall cell lung cancer by integration of the cancer cell secretome and tissue transcriptome data sets. Knockdown of KPNA2 suppressed the proliferation and migration abilities of lung cancer cells. However, the precise molecular mechanisms underlying KPNA2 activity in cancer remain to be established. In the current study, we applied gene knockdown, subcellular fractionation, and stable isotope labeling by amino acids in cell culture-based quantitative proteomic strategies to systematically analyze the KPNA2-regulating protein profiles in an adenocarcinoma cell line. Interaction network analysis revealed that several KPNA2-regulating proteins are involved in the cell cycle, DNA metabolic process, cellular component movements and cell migration. Importantly, E2F1 was identified as a potential novel cargo of KPNA2 in the nuclear proteome. The mRNA levels of potential effectors of E2F1 measured using quantitative PCR indicated that E2F1 is one of the "master molecule" responses to KPNA2 knockdown. Immunofluorescence staining and immunoprecipitation assays disclosed co-localization and association between E2F1 and KPNA2. An in vitro protein binding assay further demonstrated that E2F1 interacts directly with KPNA2. Moreover, knockdown of KPNA2 led to subcellular redistribution of E2F1 in lung cancer cells. Our results collectively demonstrate the utility of quantitative proteomic approaches and provide a fundamental platform to further explore the biological roles of KPNA2 in nonsmall cell lung cancer.

Distinct roles for classical nuclear import receptors in the growth of multinucleated muscle cells

Proper muscle function is dependent on spatial and temporal control of gene expression in myofibers. Myofibers are multinucleated cells that are formed, repaired and maintained by the process of myogenesis in which progenitor myoblasts proliferate, differentiate and fuse. Gene expression is dependent upon proteins that require facilitated nuclear import, however little is known about the regulation of nucleocytoplasmic transport during the formation of myofibers. We analyzed the role of karyopherin alpha (KPNA), a key classical nuclear import receptor, during myogenesis. We established that five karyopherin alpha paralogs are expressed by primary mouse myoblasts in vitro and that their steady-state levels increase in multinucleated myotubes, suggesting a global increase in demand for classical nuclear import during myogenesis. We used siRNA-mediated knockdown to identify paralog-specific roles for KPNA1 and KPNA2 during myogenesis. KPNA1 knockdown increased myoblast proliferation, whereas KPNA2 knockdown decreased proliferation. In contrast, no proliferation defect was observed with KPNA4 knockdown. Only knockdown of KPNA2 decreased myotube growth. These results identify distinct pathways involved in myoblast proliferation and myotube growth that rely on specific nuclear import receptors suggesting that regulation of classical nuclear import pathways likely plays a critical role in controlling gene expression in skeletal muscle.

Karyopherin alpha 2 (KPNA2) is associated with the natural resistance to Schistosoma japanicum infection in Microtus fortis

Microtus fortis is a naturally vertebrate host resistant to Schistosoma japonicum infection. In order to understand the molecular mechanism and identify the molecules related to the natural resistance to S. japanicum infection of M. fortis, we screened a gene pool named gE76 by expression cloning and proved it to have high anti-schistosomula effects in our previous work. In this study we identified a clone named gE76.44. We found that the conditioned medium of pcDNA1.1-gE76.44 caused 14.0% schistosomula death rate in 96 h, which was significantly higher than that of negative control (P<0.05). The gE76.44 was sequenced and the full-length cDNA was 2008 bp with ORF of 1590bp encoding a polypeptide of 529 amino acid residues. Bioinformatics analysis indicated it was the homologue of karyopherin alpha 2 (KPNA2). To further confirm its anti-schistosome activity, we inserted full length of Mf-KPNA2 (KPNA2 of M. fortis) gene into a retroviral expression vector pLXSN and packaged the recombinant virus with PA317 cells. Mice infected with S. japanicum cercariae were administrated by intravenous injection through tail vein and treated with pLXSN-KPNA2. Adult worms and egg reduction were counted after heart perfusion of mice 42 d after infection. We found that compared with the control, mice injected with Mf-KPNA2 had 39.42% worm burden reduction and 76.50% reduction in LEPG (liver eggs per gram) (P<0.01), indicating its anti-schistosome effect of Mf-KPNA2 in vivo. Taken together, the results suggested Mf-KPNA2 as a novel anti-schistosome molecule in vitro and in vivo.

Common importin alpha specificity for papillomavirus E2 proteins

Papillomaviruses infect keratinocytes and their reproduction is tied to differentiation of the skin. The E2 protein of papillomaviruses is a multifunctional early protein that binds specifically to the viral DNA to regulate genome transcription, replication, and segregation. All of these are nuclear events that require specific transport of E2 into the host nucleus. Nuclear localization signal (NLS) sequences have been mapped for several E2 proteins, and these sequences resemble motifs that interact with cellular transport adaptor molecules termed alpha importins. To determine which importins could carry E2 proteins, in vitro binding studies were performed with three different E2 proteins and the five ubiquitous alpha importins. The E2 proteins preferentially interacted with alpha importins 3 and 5, and showed very weak or no interaction with the other three widely expressed alpha importins (alpha1, alpha 4, and alpha 7). While all five alpha importins appear to be constitutively expressed in keratinocytes, during differentiation of a human keratinocyte line (HaCaT) we observed a specific increase in expression of alphas 3 and 5. This differentiation-specific increase in alpha 3 and alpha 5 expression suggests that preferential usage of these two importins by E2 may facilitate E2 nuclear uptake during terminal differentiation.

Analysis of newly established EST databases reveals similarities between heart regeneration in newt and fish

BACKGROUND

The newt Notophthalmus viridescens possesses the remarkable ability to respond to cardiac damage by formation of new myocardial tissue. Surprisingly little is known about changes in gene activities that occur during the course of regeneration. To begin to decipher the molecular processes, that underlie restoration of functional cardiac tissue, we generated an EST database from regenerating newt hearts and compared the transcriptional profile of selected candidates with genes deregulated during zebrafish heart regeneration.

RESULTS

A cDNA library of 100,000 cDNA clones was generated from newt hearts 14 days after ventricular injury. Sequencing of 11520 cDNA clones resulted in 2894 assembled contigs. BLAST searches revealed 1695 sequences with potential homology to sequences from the NCBI database. BLAST searches to TrEMBL and Swiss-Prot databases assigned 1116 proteins to Gene Ontology terms. We also identified a relatively large set of 174 ORFs, which are likely to be unique for urodele amphibians. Expression analysis of newt-zebrafish homologues confirmed the deregulation of selected genes during heart regeneration. Sequences, BLAST results and GO annotations were visualized in a relational web based database followed by grouping of identified proteins into clusters of GO Terms. Comparison of data from regenerating zebrafish hearts identified biological processes, which were uniformly overrepresented during cardiac regeneration in newt and zebrafish.

CONCLUSION

We concluded that heart regeneration in newts and zebrafish led to the activation of similar sets of genes, which suggests that heart regeneration in both species might follow similar principles. The design of the newly established newt EST database allows identification of molecular pathways important for heart regeneration.

Toxicogenomic analysis of mainstream tobacco smoke-exposed mice reveals repression of plasminogen activator inhibitor-1 gene in heart

Tobacco smoking is associated with cardiovascular pathology. However, the molecular mechanisms of tobacco smoke exposure that lead to initiation or exacerbation of cardiovascular disease are unclear. In this study, the effects of mainstream tobacco smoke (MTS) on global transcription in the heart were investigated. Male C57B1/CBA mice were exposed to MTS from 2 cigarettes daily, 5 days/wk for 6 or 12 wk. Mice were sacrificed immediately, or 6 wk following the last cigarette. High-density DNA microarrays were used to characterize global gene expression changes in whole heart. Fifteen genes were significantly differentially expressed following exposure to MTS. Among these genes, cytochrome P-450 1A1 (Cyp1A1) was upregulated by 12-fold, and Serpine-1 (plasminogen activator inhibitor-1, PAI-1) was downregulated by 1.7-fold. Concomitant increase in Cyp1A1 protein levels and decrease in total and active PAI-1 protein was observed in tissue extracts by Western blot assay and enzyme-linked immunosorbent assay (ELISA), respectively. Observed changes were transient and were partially reversed during break periods. Thus, gene expression profiling of heart tissue revealed a novel cardiovascular mechanism operating in response to MTS. Our results suggest a potential role for PAI-1 in MTS-induced cardiovascular pathology.

Importins and exportins in cellular differentiation

The importin/exportin transport system provides the machinery involved in nucleocytoplasmic transport. Alterations of the levels of importins and exportins may play crucial roles in development, differentiation and transformation. Employing human leukaemia HL-60 cells, we and others have revealed the differentiation-associated changes in the protein and gene expression of these factors. The recent finding that a switch to the importin-α subtype triggers neural differentiation of embryonic stem cells underscores the importance of nucleocytoplasmic transport factors in cellular events. This review focuses on current research into the roles of importins and exportins in cell differentiation.

Genetic networks of cooperative redox regulation of osteopontin

Osteopontin is a primary cytokine and matrix-associated protein involved in medial thickening and neointima formation. Osteopontin binds integrin receptors, activates cell migration and matrix metalloproteinases, and mediates arteriosclerotic lesion formation and vessel calcification. To understand the complex biology of osteopontin, computational methodology was employed to identify sets of genes whose transcriptional states were predictive of osteopontin gene expression based on the transcriptional states of 12,400 genes and ESTs across 235 independent Affymetrix Murine Genome Array MG_U74Av2 hybridizations. Arginase [GenBank: U51805] and Mac-2 antigen [GenBank: X16834] were identified as primary attractors within the gene-gene interaction network of osteopontin. Resolution of molecular interactions among these genes indicated that the majority of predictor genes could be linked through redox regulated transcription by nuclear factor kappa-B and transforming growth factor beta inducible early gene 1 regulatory elements. Subsequent molecular analyses established redox sensitivity of a 200 bp region within the 5' UTR of opn promoter and implicated nuclear factor kappa-B and transforming growth factor beta inducible early gene 1 cis-acting elements in the regulation of osteopontin.