scholarly journals Transportin-2 plays a critical role in nucleocytoplasmic shuttling of oestrogen receptor-α

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tetsuji Moriyama ◽  
Yoshihiro Yoneda ◽  
Masahiro Oka ◽  
Masami Yamada
Keyword(s):  
Nuclear Export ◽  
Oestrogen Receptor ◽  
Critical Role ◽  
Phosphatidylinositol 3 Kinase ◽  
Nucleocytoplasmic Shuttling ◽  
Nuclear Localisation Signal ◽  
Nuclear Localisation ◽  
Akt Phosphorylation ◽  
Importin Α ◽  
Oestrogen Receptor Α

Abstract Oestrogen receptor-α (ERα) shuttles continuously between the nucleus and the cytoplasm, and functions as an oestrogen-dependent transcription factor in the nucleus and as an active mediator of signalling pathways, such as phosphatidylinositol 3-kinase (PI3K)/AKT, in the cytoplasm. However, little is known regarding the mechanism of ERα nucleocytoplasmic shuttling. In this study, we found that ERα is transported into the nucleus by importin-α/β1. Furthermore, we found that Transportin-2 (TNPO2) is involved in 17β-oestradiol (E2)-dependent cytoplasmic localisation of ERα. Interestingly, it was found that TNPO2 does not mediate nuclear export, but rather is involved in the cytoplasmic retention of ERα via the proline/tyrosine (PY) motifs. Moreover, we found that TNPO2 competitively binds to the basic nuclear localisation signal (NLS) of ERα with importin-α to inhibit importin-α/β-dependent ERα nuclear import. Finally, we confirmed that TNPO2 knockdown enhances the nuclear localisation of wild-type ERα and reduces PI3K/AKT phosphorylation in the presence of E2. These results reveal that TNPO2 regulates nucleocytoplasmic shuttling and cytoplasmic retention of ERα, so that ERα has precise functions depending on the stimulation.

scholarly journals Analysis of Cellular Factors That Mediate Nuclear Export of RNAs Bearing the Mason-Pfizer Monkey Virus Constitutive Transport Element

2000 ◽  
Vol 74 (13) ◽  
pp. 5863-5871 ◽  
Author(s):  
Yibin Kang ◽  
Hal P. Bogerd ◽  
Bryan R. Cullen
Keyword(s):  
Nuclear Export ◽  
Biological Activities ◽  
Critical Role ◽  
Nuclear Pore ◽  
Nucleocytoplasmic Shuttling ◽  
Rna Molecules ◽  
Constitutive Transport Element ◽  
Rna Export

ABSTRACT There is now convincing evidence that the human Tap protein plays a critical role in mediating the nuclear export of mRNAs that contain the Mason-Pfizer monkey virus constitutive transport element (CTE) and significant evidence that Tap also participates in global poly(A)+ RNA export. Previously, we had mapped carboxy-terminal sequences in Tap that serve as an essential nucleocytoplasmic shuttling domain, while others had defined an overlapping Tap sequence that can bind to the FG repeat domains of certain nucleoporins. Here, we demonstrate that these two biological activities are functionally correlated. Specifically, mutations in Tap that block nucleoporin binding also block both nucleocytoplasmic shuttling and the Tap-dependent nuclear export of CTE-containing RNAs. In contrast, mutations that do not inhibit nucleoporin binding also fail to affect Tap shuttling. Together, these data indicate that Tap belongs to a novel class of RNA export factors that can target bound RNA molecules directly to the nuclear pore without the assistance of an importin β-like cofactor. In addition to nucleoporins, Tap has also been proposed to interact with a cellular cofactor termed p15. Although we were able to confirm that Tap can indeed bind p15 specifically both in vivo and in vitro, a mutation in Tap that blocked p15 binding only modestly inhibited CTE-dependent nuclear RNA export. However, p15 did significantly enhance the affinity of Tap for the CTE in vitro and readily formed a ternary complex with Tap on the CTE. This result suggests that p15 may play a significant role in the recruitment of the Tap nuclear export factor to target RNA molecules in vivo.

scholarly journals The Nucleoporin Nup153 Plays a Critical Role in Multiple Types of Nuclear Export

1999 ◽  
Vol 10 (3) ◽  
pp. 649-664 ◽  
Author(s):  
Katharine S. Ullman ◽  
Sundeep Shah ◽  
Maureen A. Powers ◽  
Douglass J. Forbes
Keyword(s):  
Nuclear Export ◽  
Critical Role ◽  
Adaptor Protein ◽  
Nucleocytoplasmic Transport ◽  
Protein Export ◽  
Nuclear Pore ◽  
Physical Interaction ◽  
Receptor Complexes ◽  
Importin Α ◽  
Rna Export

The fundamental process of nucleocytoplasmic transport takes place through the nuclear pore. Peripheral pore structures are presumably poised to interact with transport receptors and their cargo as these receptor complexes first encounter the pore. One such peripheral structure likely to play an important role in nuclear export is the basket structure located on the nuclear side of the pore. At present, Nup153 is the only nucleoporin known to localize to the surface of this basket, suggesting that Nup153 is potentially one of the first pore components an RNA or protein encounters during export. In this study, anti-Nup153 antibodies were used to probe the role of Nup153 in nuclear export in Xenopus oocytes. We found that Nup153 antibodies block three major classes of RNA export, that of snRNA, mRNA, and 5S rRNA. Nup153 antibodies also block the NES protein export pathway, specifically the export of the HIV Rev protein, as well as Rev-dependent RNA export. Not all export was blocked; Nup153 antibodies did not impede the export of tRNA or the recycling of importin β to the cytoplasm. The specific antibodies used here also did not affect nuclear import, whether mediated by importin α/β or by transportin. Overall, the results indicate that Nup153 is crucial to multiple classes of RNA and protein export, being involved at a vital juncture point in their export pathways. This juncture point appears to be one that is bypassed by tRNA during its export. We asked whether a physical interaction between RNA and Nup153 could be observed, using homoribopolymers as sequence-independent probes for interaction. Nup153, unlike four other nucleoporins including Nup98, associated strongly with poly(G) and significantly with poly(U). Thus, Nup153 is unique among the nucleoporins tested in its ability to interact with RNA and must do so either directly or indirectly through an adaptor protein. These results suggest a unique mechanistic role for Nup153 in the export of multiple cargos.

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

2001 ◽  
Vol 75 (7) ◽  
pp. 3404-3412 ◽  
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.

Nucleocytoplasmic Shuttling of Porcine Parvovirus NS1 Protein Mediated by the CRM1 Nuclear Export Pathway and the Importin α/β Nuclear Import Pathway

2021 ◽  
Author(s):  
Liyan Cao ◽  
Fang Fu ◽  
Jianfei Chen ◽  
Hongyan Shi ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nuclear Import ◽  
Nuclear Export ◽  
Nonstructural Protein ◽  
Nuclear Pore ◽  
Porcine Parvovirus ◽  
Ns1 Protein ◽  
Nucleocytoplasmic Shuttling ◽  
Export Pathway ◽  
Importin Α

Porcine parvovirus (PPV) NS1, the major nonstructural protein of this virus, plays an important role in PPV replication. We show, for the first time, that NS1 dynamically shuttles between the nucleus and cytoplasm, although its subcellular localization is predominantly nuclear. NS1 contains two nuclear export signals (NESs) at amino acids 283–291 (designated NES2) and 602–608 (designated NES1). NES1 and NES2 are both functional and transferable NESs, and their nuclear export activity is blocked by leptomycin B (LMB), suggesting that the export of NS1 from the nucleus is dependent upon the chromosome region maintenance 1 (CRM1) pathway. Deletion and site-directed mutational analyses showed that NS1 contains a bipartite nuclear localization signal (NLS) at amino acids 256–274. Coimmunoprecipitation assays showed that NS1 interacts with importins α5 and α7 through its NLS. The overexpression of CRM1, importins α5 and α7 significantly promoted PPV replication, whereas the inhibition of CRM1 and importin α/β-mediated transport by specific inhibitors (LMB, importazole and ivermectin) clearly blocked PPV replication. The mutant viruses of delete NESs or NLS motif of the NS1 by using reverse genetics could not be rescued, suggesting that NESs and NLS are essential for PPV replication. Collectively, these findings suggest that NS1 shuttles between the nucleus and cytoplasm, mediated by its functional NESs and NLS, via the CRM1-dependent nuclear export pathway and the importin α/β-mediated nuclear import pathway, and PPV proliferation was inhibited if blocking NS1 nuclear import or export. Importance PPV replicates in the nucleus, and the nuclear envelope is a barrier to its entry into and egress from the nucleus. PPV NS1 is a nucleus-targeting protein that is important for viral DNA replication. Because the NS1 molecule is large (> 50 kDa), it cannot pass through the nuclear pore complex by diffusion alone, and requires specific transport receptors to permit its nucleocytoplasmic shuttling. In this study, the two functional NESs in the NS1 protein were identified, and its dependence on the CRM1 pathway for nuclear export demonstrated. The nuclear import of NS1 utilizes importins α5 and α7 in the importin α/β nuclear import pathway.

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

2012 ◽  
Vol 393 (3) ◽  
pp. 149-160 ◽  
Author(s):  
Rüdiger Meyer ◽  
Marcus M. Nalaskowski ◽  
Patrick Ehm ◽  
Constantin Schröder ◽  
Xenia Naj ◽  
...  
Keyword(s):  
Nuclear Import ◽  
Nuclear Export ◽  
Inositol Phosphate ◽  
Nuclear Export Signal ◽  
Phosphatidylinositol 3 Kinase ◽  
Nucleocytoplasmic Shuttling ◽  
Multifunctional Protein ◽  
Intracellular Targeting ◽  
Cellular Signal ◽  
Nuclear Export Receptor

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.

Crystal structure of importin-α bound to a peptide bearing the nuclear localisation signal from chloride intracellular channel protein 4

FEBS Journal ◽  
2011 ◽  
Vol 278 (10) ◽  
pp. 1662-1675 ◽  
Author(s):  
Andrew V. Mynott ◽  
Stephen J. Harrop ◽  
Louise J. Brown ◽  
Samuel N. Breit ◽  
Bostjan Kobe ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Nuclear Localisation Signal ◽  
Nuclear Localisation ◽  
Channel Protein ◽  
Importin Α ◽  
Intracellular Channel

scholarly journals STRADα Regulates LKB1 Localization by Blocking Access to Importin-α, and by Association with Crm1 and Exportin-7

2008 ◽  
Vol 19 (4) ◽  
pp. 1614-1626 ◽  
Author(s):  
Julia Dorfman ◽  
Ian G. Macara
Keyword(s):  
Catalytic Activity ◽  
Cell Polarity ◽  
Nuclear Export ◽  
Nucleocytoplasmic Transport ◽  
Cellular Distribution ◽  
Nucleocytoplasmic Shuttling ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Importin Α ◽  
Export Receptors

LKB1, a serine/threonine kinase, regulates cell polarity, metabolism, and cell growth. The activity and cellular distribution of LKB1 are determined by cofactors, STRADα and MO25. STRADα induces relocalization of LKB1 from the nucleus to the cytoplasm and stimulates its catalytic activity. MO25 stabilizes the STRADα/LKB1 interaction. We investigated the mechanism of nucleocytoplasmic transport of LKB1 in response to its cofactors. Although LKB1 is imported into the nucleus by importin-α/β, STRADα and MO25 passively diffuse between the nucleus and the cytoplasm. STRADα induces nucleocytoplasmic shuttling of LKB1. STRADα facilitates nuclear export of LKB1 by serving as an adaptor between LKB1 and exportins CRM1 and exportin7. STRADα inhibits import of LKB1 by competing with importin-α for binding to LKB1. MO25 stabilizes the LKB1–STRADα complex but it does not facilitate its nucleocytoplasmic shuttling. Strikingly, the STRADβ, isoform which differs from STRADα in the N- and C-terminal domains that are responsible for interaction with export receptors, does not efficiently relocalize LKB1 from the nucleus to the cytoplasm. These results identify a multifactored mechanism to control LKB1 localization, and they suggest that the STRADβ-LKB1 complex might possess unique functions in the nucleus.

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

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.

scholarly journals Targeting novel LSD1-dependent ACE2 demethylation domains inhibits SARS-CoV-2 replication

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wen Juan Tu ◽  
Robert D. McCuaig ◽  
Michelle Melino ◽  
Daniel J. Rawle ◽  
Thuy T. Le ◽  
...  
Keyword(s):  
Viral Replication ◽  
Treatment Options ◽  
Critical Role ◽  
Post Exposure Prophylaxis ◽  
Nuclear Entry ◽  
Importin Α ◽  
Active Transcription ◽  
Nuclear Shuttling ◽  
Asymptomatic Phase ◽  
Exposure Prophylaxis

AbstractTreatment options for COVID-19 remain limited, especially during the early or asymptomatic phase. Here, we report a novel SARS-CoV-2 viral replication mechanism mediated by interactions between ACE2 and the epigenetic eraser enzyme LSD1, and its interplay with the nuclear shuttling importin pathway. Recent studies have shown a critical role for the importin pathway in SARS-CoV-2 infection, and many RNA viruses hijack this axis to re-direct host cell transcription. LSD1 colocalized with ACE2 at the cell surface to maintain demethylated SARS-CoV-2 spike receptor-binding domain lysine 31 to promote virus–ACE2 interactions. Two newly developed peptide inhibitors competitively inhibited virus–ACE2 interactions, and demethylase access to significantly inhibit viral replication. Similar to some other predominantly plasma membrane proteins, ACE2 had a novel nuclear function: its cytoplasmic domain harbors a nuclear shuttling domain, which when demethylated by LSD1 promoted importin-α-dependent nuclear ACE2 entry following infection to regulate active transcription. A novel, cell permeable ACE2 peptide inhibitor prevented ACE2 nuclear entry, significantly inhibiting viral replication in SARS-CoV-2-infected cell lines, outperforming other LSD1 inhibitors. These data raise the prospect of post-exposure prophylaxis for SARS-CoV-2, either through repurposed LSD1 inhibitors or new, nuclear-specific ACE2 inhibitors.

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