Nucleocytoplasmic shuttling of human inositol phosphate multikinase is influenced by CK2 phosphorylation

Abstract Human inositol phosphate multikinase (IPMK) is a multifunctional protein in cellular signal transduction, namely, a multispecific inositol phosphate kinase, phosphatidylinositol 3-kinase, and a scaffold within the mTOR-raptor complex. To fulfill these nuclear and cytoplasmic functions, intracellular targeting of IPMK needs to be regulated. We show here that IPMK, which has been considered to be a preferentially nuclear protein, is a nucleocytoplasmic shuttling protein, whose nuclear export is mediated by classical nuclear export receptor CRM1. We identified a functional nuclear export signal (NES) additionally to its previously described nuclear import signal (NLS). Furthermore, we describe a mechanism by which the activity of the IPMK-NLS is controlled. Protein kinase CK2 binds endogenous IPMK and phosphorylates it at serine 284. Interestingly, this phosphorylation can decrease nuclear localization of IPMK cell type specifically. A controlled nuclear import of IPMK may direct its actions either toward nuclear inositol phosphate (InsPx) metabolism or cytoplasmic actions on InsPx, phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2], as well as mTOR-raptor.

Download Full-text

The Nup98-HoxA9 Leukemogenic Fusion Protein Blocks Xpo1 and Tap-Mediated Nuclear Export

Blood ◽

10.1182/blood.v118.21.5228.5228 ◽

2011 ◽

Vol 118 (21) ◽

pp. 5228-5228

Author(s):

Yildirim Dogan ◽

Sutapa Sahay ◽

David C Dorn ◽

Anna Franceschino ◽

Michael Xu ◽

...

Keyword(s):

Nuclear Export ◽

Conflicts Of Interest ◽

Blast Crisis ◽

Nuclear Export Signal ◽

Nucleocytoplasmic Shuttling ◽

Nuclear Trafficking ◽

Myeloid Leukemias ◽

Nuclear Export Receptor ◽

Export Signal

Abstract Abstract 5228 In leukemia Nup98 fusion genes are found as a product of the reciprocal translocation between Nucleoporin 98 (nup98) and homeobox-cluster genes. Nup98-HoxA9 (NHA9), the product of the t(7;11) translocation, is detected in acute myeloid leukemias (AMLs) and as a secondary abnormality in blast crisis of chronic myeloid leukemia (CML). The role of NHA9 in leukemogenesis is complex and incompletely understood. Here, we show an abrogation of nucleocytoplasmic shuttling of the nuclear export receptor Xpo1 and Tap in NHA9-expressing cells by using retroviral nuclear trafficking as a model. Lentiviral Rev, the prototype for nuclear export signal (NES)-containing proteins is shuttled through the nucleopore by Xpo1. NHA9 sequestered Xpo1 from the nuclear rim into nuclear aggregates resulting in deficient Xpo1-dependent nuclear exit of Rev and its mRNA substrates. Tap is involved in mRNA nucleocytoplasmic shuttling and is also responsible for the nuclear export of D-type retrovirus CTE-mRNAs. By using Tap/CTE-mRNA nuclear export as a model we also found that Tap colocalized in NHA9 nuclear aggregates leading to impaired Tap-mediated nuclear exit of CTE-mRNA substrates. Leukemogenicity of Nup98 fusion proteins may be accounted for in part by defects in Tap and Xpo1-mediated export of their substrates. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

PSPC1 is a new contextual determinant of aberrant subcellular translocation of oncogenes in tumor progression

Journal of Biomedical Science ◽

10.1186/s12929-021-00753-3 ◽

2021 ◽

Vol 28 (1) ◽

Author(s):

Yaw-Dong Lang ◽

Yuh-Shan Jou

Keyword(s):

Nuclear Export ◽

Synergistic Effects ◽

Therapeutic Option ◽

Nucleocytoplasmic Shuttling ◽

Innovative Strategy ◽

Fda Approval ◽

Cargo Proteins ◽

The Common ◽

Contextual Determinants ◽

Nuclear Export Receptor

AbstractDysregulation of nucleocytoplasmic shuttling is commonly observed in cancers and emerging as a cancer hallmark for the development of anticancer therapeutic strategies. Despite its severe adverse effects, selinexor, a selective first-in-class inhibitor of the common nuclear export receptor XPO1, was developed to target nucleocytoplasmic protein shuttling and received accelerated FDA approval in 2019 in combination with dexamethasone as a fifth-line therapeutic option for adults with relapsed refractory multiple myeloma (RRMM). To explore innovative targets in nucleocytoplasmic shuttling, we propose that the aberrant contextual determinants of nucleocytoplasmic shuttling, such as PSPC1 (Paraspeckle component 1), TGIF1 (TGF-β Induced Factor Homeobox 1), NPM1 (Nucleophosmin), Mortalin and EBP50, that modulate shuttling (or cargo) proteins with opposite tumorigenic functions in different subcellular locations could be theranostic targets for developing anticancer strategies. For instance, PSPC1 was recently shown to be the contextual determinant of the TGF-β prometastatic switch and PTK6/β-catenin reciprocal oncogenic nucleocytoplasmic shuttling during hepatocellular carcinoma (HCC) progression. The innovative nucleocytoplasmic shuttling inhibitor PSPC1 C-terminal 131 polypeptide (PSPC1-CT131), which was developed to target both the shuttling determinant PSPC1 and the shuttling protein PTK6, maintained their tumor-suppressive characteristics and exhibited synergistic effects on tumor suppression in HCC cells and mouse models. In summary, targeting the contextual determinants of nucleocytoplasmic shuttling with cargo proteins having opposite tumorigenic functions in different subcellular locations could be an innovative strategy for developing new therapeutic biomarkers and agents to improve cancer therapy.

Download Full-text

Nuclear Import of IκBα Is Accomplished by a Ran-Independent Transport Pathway

Molecular and Cellular Biology ◽

10.1128/mcb.20.5.1571-1582.2000 ◽

2000 ◽

Vol 20 (5) ◽

pp. 1571-1582 ◽

Cited By ~ 49

Author(s):

Shrikesh Sachdev ◽

Sriparna Bagchi ◽

Donna D. Zhang ◽

Angela C. Mings ◽

Mark Hannink

Keyword(s):

Nuclear Import ◽

Nuclear Export ◽

Dominant Negative ◽

Dominant Negative Mutant ◽

Nuclear Pore ◽

Transport Pathway ◽

Repeat Domain ◽

Nuclear Export Receptor

ABSTRACT The inhibitor of kappa B alpha (IκBα) protein is able to shuttle between the cytoplasm and the nucleus. We have utilized a combination of in vivo and in vitro approaches to provide mechanistic insight into nucleocytoplasmic shuttling by IκBα. IκBα contains multiple functional domains that contribute to shuttling of IκBα between the cytoplasm and the nucleus. Nuclear import of IκBα is mediated by the central ankyrin repeat domain. Similar to previously described nuclear import pathways, nuclear import of IκBα is temperature and ATP dependent and is blocked by a dominant-negative mutant of importin β. However, in contrast to classical nuclear import pathways, nuclear import of IκBα is independent of soluble cytosolic factors and is not blocked by the dominant-negative RanQ69L protein. Nuclear export of IκBα is mediated by an N-terminal nuclear export sequence. Nuclear export of IκBα requires the CRM1 nuclear export receptor and is blocked by the dominant-negative RanQ69L protein. Our results are consistent with a model in which nuclear import of IκBα is mediated through direct interactions with components of the nuclear pore complex, while nuclear export of IκBα is mediated via a CRM1-dependent pathway.

Download Full-text

RNA-Regulated Interaction of Transportin-1 and Exportin-5 with the Double-Stranded RNA-Binding Domain Regulates Nucleocytoplasmic Shuttling of ADAR1

Molecular and Cellular Biology ◽

10.1128/mcb.01519-08 ◽

2009 ◽

Vol 29 (6) ◽

pp. 1487-1497 ◽

Cited By ~ 72

Author(s):

Jutta Fritz ◽

Alexander Strehblow ◽

Andreas Taschner ◽

Sandy Schopoff ◽

Pawel Pasierbek ◽

...

Keyword(s):

Nuclear Export ◽

Rna Binding ◽

Nuclear Export Signal ◽

Nucleocytoplasmic Transport ◽

Nucleocytoplasmic Shuttling ◽

Double Stranded Rna ◽

Binding Domains ◽

Dsrna Binding ◽

Localization Signal ◽

Editing Enzyme

ABSTRACT Double-stranded RNA (dsRNA)-binding proteins interact with substrate RNAs via dsRNA-binding domains (dsRBDs). Several proteins harboring these domains exhibit nucleocytoplasmic shuttling and possibly remain associated with their substrate RNAs bound in the nucleus during nuclear export. In the human RNA-editing enzyme ADAR1-c, the nuclear localization signal overlaps the third dsRBD, while the corresponding import factor is unknown. The protein also lacks a clear nuclear export signal but shuttles between the nucleus and the cytoplasm. Here we identify transportin-1 as the import receptor for ADAR1. Interestingly, dsRNA binding interferes with transportin-1 binding. At the same time, each of the dsRBDs in ADAR1 interacts with the export factor exportin-5. RNA binding stimulates this interaction but is not a prerequisite. Thus, our data demonstrate a role for some dsRBDs as RNA-sensitive nucleocytoplasmic transport signals. dsRBD3 in ADAR1 can mediate nuclear import, while interaction of all dsRBDs might control nuclear export. This finding may have implications for other proteins containing dsRBDs and suggests a selective nuclear export mechanism for substrates interacting with these proteins.

Download Full-text

Involvement of Nucleocytoplasmic Shuttling of Yeast Nap1 in Mitotic Progression

Molecular and Cellular Biology ◽

10.1128/mcb.23.18.6672-6684.2003 ◽

2003 ◽

Vol 23 (18) ◽

pp. 6672-6684 ◽

Cited By ~ 40

Author(s):

Mary Miyaji-Yamaguchi ◽

Kohsuke Kato ◽

Ryosuke Nakano ◽

Tomohiro Akashi ◽

Akihiko Kikuchi ◽

...

Keyword(s):

Nuclear Export ◽

Nuclear Export Signal ◽

Temperature Sensitive ◽

Nucleosome Assembly ◽

Mitotic Progression ◽

Nucleocytoplasmic Shuttling ◽

Nucleosome Formation ◽

Mitotic Cyclin ◽

Carboxy Terminal

ABSTRACT Nucleosome assembly protein 1 (Nap1) is widely conserved from yeasts to humans and facilitates nucleosome formation in vitro as a histone chaperone. Nap1 is generally localized in the cytoplasm, except that subcellular localization of Drosophila melanogaster Nap1 is dynamically regulated between the cytoplasm and nucleus during early development. The cytoplasmic localization of Nap1 is seemingly incompatible with the proposed role of Nap1 in nucleosome formation, which should occur in the nucleus. Here, we have examined the roles of a putative nuclear export signal (NES) sequence in yeast Nap1 (yNap1). yNap1 mutants lacking the NES-like sequence were localized predominantly in the nucleus. Deletion of NAP1 in cells harboring a single mitotic cyclin gene is known to cause mitotic delay and temperature-sensitive growth. A wild-type NAP1 complemented these phenotypes while nap1 mutant genes lacking the NES-like sequence or carboxy-terminal region did not. These and other results suggest that yNap1 is a nucleocytoplasmic shuttling protein and that its shuttling is important for yNap1 function during mitotic progression. This study also provides a possible explanation for Nap1's involvement in nucleosome assembly and/or remodeling in the nucleus.

Download Full-text

Nucleocytoplasmic Trafficking of G2/M Regulators in Yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e08-03-0286 ◽

2008 ◽

Vol 19 (9) ◽

pp. 4006-4018 ◽

Cited By ~ 25

Author(s):

Mignon A. Keaton ◽

Lee Szkotnicki ◽

Aron R. Marquitz ◽

Jake Harrison ◽

Trevin R. Zyla ◽

...

Keyword(s):

Cell Cycle ◽

Nuclear Import ◽

Nuclear Export ◽

Cell Cycle Regulators ◽

Cyclin Dependent Kinase ◽

Nucleocytoplasmic Trafficking ◽

Nucleocytoplasmic Shuttling ◽

Upstream Regulator ◽

Cellular Compartments ◽

Cdk Regulation

Nucleocytoplasmic shuttling is prevalent among many cell cycle regulators controlling the G2/M transition. Shuttling of cyclin/cyclin-dependent kinase (CDK) complexes is thought to provide access to substrates stably located in either compartment. Because cyclin/CDK shuttles between cellular compartments, an upstream regulator that is fixed in one compartment could in principle affect the entire cyclin/CDK pool. Alternatively, the regulators themselves may need to shuttle to effectively regulate their moving target. Here, we identify localization motifs in the budding yeast Swe1p (Wee1) and Mih1p (Cdc25) cell cycle regulators. Replacement of endogenous Swe1p or Mih1p with mutants impaired in nuclear import or export revealed that the nuclear pools of Swe1p and Mih1p were more effective in CDK regulation than were the cytoplasmic pools. Nevertheless, shuttling of cyclin/CDK complexes was sufficiently rapid to coordinate nuclear and cytoplasmic events even when Swe1p or Mih1p were restricted to one compartment. Additionally, we found that Swe1p nuclear export was important for its degradation. Because Swe1p degradation is regulated by cytoskeletal stress, shuttling of Swe1p between nucleus and cytoplasm serves to couple cytoplasmic stress to nuclear cyclin/CDK inhibition.

Download Full-text

Mice develop normally in the absence of Smad4 nucleocytoplasmic shuttling

Biochemical Journal ◽

10.1042/bj20061830 ◽

2007 ◽

Vol 404 (2) ◽

pp. 235-245 ◽

Cited By ~ 12

Author(s):

Christine A. Biondi ◽

Debipriya Das ◽

Michael Howell ◽

Ayesha Islam ◽

Elizabeth K. Bikoff ◽

...

Keyword(s):

Transcriptional Activation ◽

Nuclear Export ◽

Transforming Growth Factor ◽

Es Cells ◽

Nuclear Export Signal ◽

Embryonic Stem ◽

Nucleocytoplasmic Shuttling ◽

Mouse Development ◽

Developmental Defects

Smad4 in partnership with R-Smads (receptor-regulated Smads) activates TGF-β (transforming growth factor-β)-dependent signalling pathways essential for early mouse development. Smad4 null embryos die shortly after implantation due to severe defects in cell proliferation and visceral endoderm differentiation. In the basal state, Smad4 undergoes continuous shuttling between the cytoplasm and the nucleus due to the combined activities of an N-terminal NLS (nuclear localization signal) and an NES (nuclear export signal) located in its linker region. Cell culture experiments suggest that Smad4 nucleocytoplasmic shuttling plays an important role in TGF-β signalling. In the present study we have investigated the role of Smad4 shuttling in vivo using gene targeting to engineer two independent mutations designed to eliminate Smad4 nuclear export. As predicted this results in increased levels of Smad4 in the nucleus of homozygous ES cells (embryonic stem cells) and primary keratinocytes, in the presence or absence of ligand. Neither mutation affects Smad4 expression levels nor its ability to mediate transcriptional activation in homozygous cell lines. Remarkably mouse mutants lacking the Smad4 NES develop normally. Smad4 NES mutants carrying one copy of a Smad4 null allele also fail to display developmental defects. The present study clearly demonstrates that Smad4 nucleocytoplasmic shuttling is not required for embryonic development or tissue homoeostasis in normal, healthy adult mice.

Download Full-text

The nuclear lamina is a hub for the nuclear function of Jacob

10.21203/rs.3.rs-98097/v1 ◽

2020 ◽

Author(s):

Sebastian Samer ◽

Rajeev Raman ◽

Gregor Laube ◽

Michael R. Kreutz ◽

Anna Karpova

Keyword(s):

Gene Expression ◽

Nuclear Membrane ◽

Nuclear Import ◽

Nuclear Export ◽

Nuclear Export Signal ◽

Nuclear Lamina ◽

Immunogold Electron Microscopy ◽

Core Component ◽

Inner Nuclear Membrane ◽

Export Signal

Abstract Jacob is a synapto-nuclear messenger protein that couples NMDAR activity to CREB-dependent gene expression. In this study, we investigated the nuclear distribution of Jacob and report a prominent targeting to the nuclear envelope that requires NMDAR activity and nuclear import. Immunogold electron microscopy revealed preferential association of Jacob with the inner nuclear membrane where it directly binds to LaminB1, an intermediate filament and core component of the inner nuclear membrane (INM). The association with INM is transient; it involves a functional nuclear export signal in Jacob and a canonical CRM1-/RanGTP-dependent export mechanism that defines the residing time of the protein at the INM. Taken together, the data suggest a stepwise redistribution of Jacob within the nucleus following nuclear import and prior to nuclear export.

Download Full-text

Unconventional tonicity-regulated nuclear trafficking of NFAT5 mediated by KPNB1, XPOT and RUVBL2

10.1101/2021.07.11.451941 ◽

2021 ◽

Author(s):

Chris Y. Cheung ◽

Ting-Ting Huang ◽

Ning Chow ◽

Shuqi Zhang ◽

Yanxiang Zhao ◽

...

Keyword(s):

Nuclear Import ◽

Nuclear Localization Signal ◽

Nuclear Export ◽

Nuclear Pore ◽

Nucleocytoplasmic Shuttling ◽

Proteomics Analysis ◽

Nuclear Trafficking ◽

Localization Signal ◽

Underlying Mechanisms ◽

Sirna Screening

NFAT5 is the only known mammalian tonicity-responsive transcription factor functionally implicated in diverse physiological and pathological processes. NFAT5 activity is tightly regulated by extracellular tonicity but the underlying mechanisms remain elusive. We demonstrated that NFAT5 enters the nucleus via the nuclear pore complex. We also found that NFAT5 utilizes a non-canonical nuclear localization signal (NFAT5-NLS) for nuclear imports. siRNA screening revealed that karyopherin beta-1 (KPNB1) drives nuclear import of NFAT5 via directly interacting with NFAT5-NLS. Proteomics analysis and siRNA screening further revealed that nuclear export of NFAT5 under hypotonicity is mediated by Exportin-T, and that it requires RuvB-Like AAA type ATPase 2 (RUVBL2) as an indispensable chaperone. Our findings have identified KPNB1 and RUVBL2 as key molecules responsible for the unconventional tonicity-regulated nucleocytoplasmic shuttling of NFAT5. These findings offer an opportunity for developing novel NFAT5 targeting strategies that are potentially useful for the treatment of diseases associated with NFAT5 dysregulation.

Download Full-text

Borna Disease Virus Nucleoprotein Requires both Nuclear Localization and Export Activities for Viral Nucleocytoplasmic Shuttling

Journal of Virology ◽

10.1128/jvi.75.7.3404-3412.2001 ◽

2001 ◽

Vol 75 (7) ◽

pp. 3404-3412 ◽

Cited By ~ 36

Author(s):

Takeshi Kobayashi ◽

Wataru Kamitani ◽

Guoqi Zhang ◽

Makiko Watanabe ◽

Keizo Tomonaga ◽

...

Keyword(s):

Disease Virus ◽

Nuclear Localization ◽

Nuclear Export ◽

Critical Role ◽

Nuclear Export Signal ◽

Nucleocytoplasmic Shuttling ◽

Nuclear Targeting ◽

Borna Disease Virus ◽

Export Activity ◽

Borna Disease

ABSTRACT Nuclear transport of viral nucleic acids is crucial to the life cycle of many viruses. Borna disease virus (BDV) belongs to the orderMononegavirales and replicates its RNA genome in the nucleus. Previous studies have suggested that BDV nucleoprotein (N) and phosphoprotein (P) have important functions in the nuclear import of the viral ribonucleoprotein (RNP) complexes via their nuclear targeting activity. Here, we showed that BDV N has cytoplasmic localization activity, which is mediated by a nuclear export signal (NES) within the sequence. Our analysis using deletion and substitution mutants of N revealed that NES of BDV N consists of a canonical leucine-rich motif and that the nuclear export activity of the protein is mediated through the chromosome region maintenance protein-dependent pathway. Interspecies heterokaryon assay indicated that BDV N shuttles between the nucleus and cytoplasm as a nucleocytoplasmic shuttling protein. Furthermore, interestingly, the NES region overlaps a binding site to the BDV P protein, and nuclear export of a 38-kDa form of BDV N is prevented by coexpression of P. These results suggested that BDV N has two contrary activities, nuclear localization and export activity, and plays a critical role in the nucleocytoplasmic transport of BDV RNP by interaction with other viral proteins.

Download Full-text