Nuclear import of NLS- RARα is mediated by importin α/β

Regulating Phase Transition in Neurodegenerative Diseases by Nuclear Import Receptors

RNA-binding proteins (RBPs) with a low-complexity prion-like domain (PLD) can undergo aberrant phase transitions and have been implicated in neurodegenerative diseases such as ALS and FTD. Several nuclear RBPs mislocalize to cytoplasmic inclusions in disease conditions. Impairment in nucleocytoplasmic transport is another major event observed in ageing and in neurodegenerative disorders. Nuclear import receptors (NIRs) regulate the nucleocytoplasmic transport of different RBPs bearing a nuclear localization signal by restoring their nuclear localization. NIRs can also specifically dissolve or prevent the aggregation and liquid–liquid phase separation of wild-type or disease-linked mutant RBPs, due to their chaperoning activity. This review focuses on the LLPS of intrinsically disordered proteins and the role of NIRs in regulating LLPS in neurodegeneration. This review also discusses the implication of NIRs as therapeutic agents in neurogenerative diseases.

Importin alpha 1 is required for the nucleus entry of Fowl Adenovirus serotype 4 Fiber-1 protein

Fiber-1 protein (F1) is the structural protein of Fowl Adenovirus serotype 4 (FAdV-4), which could recondite the receptors of host cytomembrane. In this study, we firstly determined that F1 protein located in nucleus of LMH cells after infection with FAdV-4. We additionally revealed that F1 protein had a classic NLS, and the NLS was required for F1 nucleus entry, which was intently associated to the 26th Pro in NLS. The time rule result indicated that some F1 proteins firstly positioned in the nucleus 6 h posttranfection, and it entirely located in the nucleus 12 h posttranfection, then it ordinarily placed in cytoplasm 18 h posttranfection by means of microscopic fluorescence observation and Western Blotting. Then after transfection with pCI-neo-flag-F1 or infection with FAdV-4, the importin alpha 1 was once investigated whether or not it was required for F1 protein nucleus entry through immunofluorescence and/or Co-IP, results demonstrated that the F1 protein and importin alpha 1 co-located in the nucleus 6 h and 12 h posttranfection. The tiers of F1 protein vicinity in nucleus have been additionally investigated after knockdown expression or overexpression of importin alpha 1, and the results further revealed that importin alpha 1 used to be required for F1 protein nucleus entry. Finally, the function of F1 protein nucleus entry was investigated by qPCR, RT-PCR and Western Blotting, and the results revealed that F1 protein nucleus location was conducive to the proliferation of FAdV-4. In summary, we firstly reveal that the F1 protein of FAdV-4 locates in nucleus infected with FAdV-4, and confirm that importin alpha 1 binds to the NLS of F1 protein to nucleus localization, which promotes the proliferation of FAdV-4.

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.

Types of nuclear localization signals and mechanisms of protein import into the nucleus

Nuclear localization signals (NLS) are generally short peptides that act as a signal fragment that mediates the transport of proteins from the cytoplasm into the nucleus. This NLS-dependent protein recognition, a process necessary for cargo proteins to pass the nuclear envelope through the nuclear pore complex, is facilitated by members of the importin superfamily. Here, we summarized the types of NLS, focused on the recently reported related proteins containing nuclear localization signals, and briefly summarized some mechanisms that do not depend on nuclear localization signals into the nucleus. Video Abstract.

Analyses of DNA Methylation Involved in the Activation of Nuclear Karyopherin Alpha 2 Leading to Identify the Progression and Prognostic Significance Across Human Breast Cancer

Background

Karyopherin alpha 2 (KPNA2) is a nuclear import factor that plays a crucial role in nucleocytoplasmic transport, as well as cell proliferation, migration, and invasion in several cancers. However, the roles of KPNA2 in breast cancer as well as the underlying molecular mechanisms have not been elucidated.

Materials and Methods

To evaluate gene expression alterations during breast carcinogenesis, KPNA2 expression was analyzed using the Gene Expression Profiling Interactive Analysis and Oncomine analyses. The correlation between methylation and expression was analyzed using the MEXPRESS tool, UALCAN cancer database, and cBioPortal browser. Then, the expression and prognostic value of KPNA2 were investigated by our own breast cancer samples using RT-PCR. KPNA2 methylation level was detected by methylation-specific PCR.

Results

We obtained the following important results. (1) KPNA2 expression was significantly higher in breast cancer than normal samples and regulated by aberrant DNA hypomethylation of promoter region. (2) Among patients with breast cancer, those with higher KPNA2 expression had a lower survival rate. (3) The major mutation type of KPNA2 in breast cancer samples was missense mutation. (4) Homer1 was able to promote breast cancer progression may be through upregulating TPX2 expression.

Conclusion

Our findings suggest that aberrant DNA hypomethylation of promoter regions contributes to the aberrant expression of KPNA2 in breast cancer, which might be a potential indicator of poor prognosis.

Targeting nuclear import and export in hematological malignancies

The transport of proteins across the nuclear membrane is a highly regulated process, essential for the cell function. This transport is actively mediated by members of the karyopherin family, termed importins, or exportins, depending on the direction of transport. These proteins play an active part in tumorigenesis, through aberrant localization of their cargoes, which include oncogenes, tumor-suppressor genes and mediators of key signal transduction pathways. Overexpression of importins and exportins is reported in many malignancies, with implications in cell growth and viability, differentiation, drug resistance, and tumor microenvironment. Given their broad significance across tumors and pathways, much effort is being put to develop specific inhibitors as a novel anticancer therapeutics. Already, selinexor, a specific inhibitor of exportin-1 (XPO1), is approved for clinical use. This review will focus on the role of importins and exportins in hematological malignancies. We will discuss current preclinical and clinical data on importins and exportins, and demonstrate how our growing understanding of their functions has identified new therapeutic targets.