scholarly journals Xpo7 negatively regulates Hedgehog signaling by exporting Gli2 from the nucleus

2020 ◽  
Author(s):  
Łukasz Markiewicz ◽  
Tomasz Uśpieński ◽  
Sylwia M. Niedziółka ◽  
Paweł Niewiadomski
Keyword(s):  
Nuclear Export ◽  
Hedgehog Signaling ◽  
Negative Regulator ◽  
Nuclear Accumulation ◽  
Gli Proteins ◽  
Protein Activator ◽  
Bidirectional Transport ◽  
Hh Signaling ◽  
Nuclear Shuttling ◽  
Nuclear Export Receptor

AbstractDynamic bidirectional transport between the nucleus and the cytoplasm is critical for the regulation of many transcription factors, whose levels inside the nucleus must be tightly controlled. Efficient shuttling across the nuclear membrane is especially crucial with regard to the Hedgehog (Hh) pathway, where the transcriptional signal depends on the fine balance between the amounts of Gli protein activator and repressor forms in the nucleus. The nuclear export machinery prevents the unchecked nuclear accumulation of Gli proteins, but the mechanistic insight into this process is limited. We show that the atypical exportin Xpo7 functions as a major nuclear export receptor that actively excludes Gli2 from the nucleus and controls the outcome of Hh signaling. We show that Xpo7 interacts with several domains of Gli2 and that this interaction is dependent on SuFu, a key negative regulator of Hh signaling. Our data pave the way for a more complete understanding of the nuclear shuttling of Gli proteins and the regulation of their transcriptional activity.

scholarly journals Shuttling Imbalance of MLF1 Results in p53 Instability and Increases Susceptibility to Oncogenic Transformation

2007 ◽  
Vol 28 (1) ◽  
pp. 422-434 ◽  
Author(s):  
Noriko Yoneda-Kato ◽  
Jun-ya Kato
Keyword(s):  
Nuclear Export ◽  
Nuclear Export Signal ◽  
Chromosomal Translocation ◽  
Nuclear Accumulation ◽  
Tumor Suppressor P53 ◽  
Oncogenic Transformation ◽  
Early Passage ◽  
Leptomycin B ◽  
Nuclear Shuttling ◽  
Export Signal

ABSTRACT Myeloid leukemia factor 1 (MLF1) stabilizes the activity of the tumor suppressor p53 by suppressing its E3 ubiquitin ligase, COP1, through a third component of the COP9 signalosome (CSN3). However, little is known about how MLF1 functions upstream of the CSN3-COP1-p53 pathway and how its deregulation by the formation of the fusion protein nucleophosmin (NPM)-MLF1, generated by t(3;5)(q25.1;q34) chromosomal translocation, leads to leukemogenesis. Here we show that MLF1 is a cytoplasmic-nuclear-shuttling protein and that its nucleolar localization on fusing with NPM prevents the full induction of p53 by both genotoxic and oncogenic cellular stress. The majority of MLF1 was located in the cytoplasm, but the treatment of cells with leptomycin B rapidly induced a nuclear accumulation of MLF1. A mutation of the nuclear export signal (NES) motif identified in the MLF1 sequence enhanced the antiproliferative activity of MLF1. The fusion of MLF1 with NPM translocated MLF1 to the nucleolus and abolished the growth-suppressing activity. The introduction of NPM-MLF1 into early-passage murine embryonic fibroblasts allowed the cells to escape from cellular senescence at a markedly earlier stage and induced neoplastic transformation in collaboration with the oncogenic form of Ras. Interestingly, disruption of the MLF1-derived NES sequence completely abolished the growth-promoting activity of NPM-MLF1 in murine fibroblasts and hematopoietic cells. Thus, our results provide important evidence that the shuttling of MLF1 is critical for the regulation of cell proliferation and a disturbance in the shuttling balance increases the cell's susceptibility to oncogenic transformation.

scholarly journals Repurposing Niclosamide for Targeting Pancreatic Cancer by Inhibiting Hh/Gli Non-Canonical Axis of Gsk3β

Cancers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 3105
Author(s):  
Jyoti B. Kaushal ◽  
Rakesh Bhatia ◽  
Ranjana K. Kanchan ◽  
Pratima Raut ◽  
Surya Mallapragada ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cell Death ◽  
Therapeutic Efficacy ◽  
Hedgehog Signaling ◽  
Negative Regulator ◽  
Phase Cell ◽  
Cycle Arrest ◽  
Hh Signaling ◽  
And Migration

Niclosamide (Nic), an FDA-approved anthelmintic drug, is reported to have anti-cancer efficacy and is being assessed in clinical trials for various solid tumors. Based on its ability to target multiple signaling pathways, in the present study, we evaluated the therapeutic efficacy of Nic on pancreatic cancer (PC) in vitro. We observed an anti-cancerous effect of this drug as shown by the G0/G1 phase cell cycle arrest, inhibition of PC cell viability, colony formation, and migration. Our results revealed the involvement of mitochondrial stress and mTORC1-dependent autophagy as the predominant players of Nic-induced PC cell death. Significant reduction of Nic-induced reactive oxygen species (ROS) and cell death in the presence of a selective autophagy inhibitor spautin-1 demonstrated autophagy as a major contributor to Nic-mediated cell death. Mechanistically, Nic inhibited the interaction between BCL2 and Beclin-1 that supported the crosstalk of autophagy and apoptosis. Further, Nic treatment resulted in Gsk3β inactivation by phosphorylating its Ser-9 residue leading to upregulation of Sufu and Gli3, thereby negatively impacting hedgehog signaling and cell survival. Nic induced autophagic cell death, and p-Gsk3b mediated Sufu/Gli3 cascade was further confirmed by Gsk3β activator, LY-294002, by rescuing inactivation of Hh signaling upon Nic treatment. These results suggested the involvement of a non-canonical mechanism of Hh signaling, where p-Gsk3β acts as a negative regulator of Hh/Gli1 cascade and a positive regulator of autophagy-mediated cell death. Overall, this study established the therapeutic efficacy of Nic for PC by targeting p-Gsk3β mediated non-canonical Hh signaling and promoting mTORC1-dependent autophagy and cell death.

scholarly journals Nuclear-Cytoplasmic Shuttling of Chibby Controls β-Catenin Signaling

2010 ◽  
Vol 21 (2) ◽  
pp. 311-322 ◽  
Author(s):  
Feng-Qian Li ◽  
Adaobi Mofunanya ◽  
Victoria Fischer ◽  
Jason Hall ◽  
Ken-Ichi Takemaru
Keyword(s):  
Nuclear Export ◽  
Intracellular Localization ◽  
Gene Activation ◽  
Nuclear Export Signal ◽  
Nuclear Accumulation ◽  
Cooperative Action ◽  
Importin Α ◽  
Localization Signal ◽  
Bona Fide ◽  
Nuclear Export Receptor

In the canonical Wnt pathway, β-catenin acts as a key coactivator that stimulates target gene expression through interaction with Tcf/Lef transcription factors. Its nuclear accumulation is the hallmark of active Wnt signaling and is frequently associated with cancers. Chibby (Cby) is an evolutionarily conserved molecule that represses β-catenin–dependent gene activation. Although Cby, in conjunction with 14-3-3 chaperones, controls β-catenin distribution, its molecular nature remains largely unclear. Here, we provide compelling evidence that Cby harbors bona fide nuclear localization signal (NLS) and nuclear export signal (NES) motifs, and constitutively shuttles between the nucleus and cytoplasm. Efficient nuclear export of Cby requires a cooperative action of the intrinsic NES, 14-3-3, and the CRM1 nuclear export receptor. Notably, 14-3-3 docking provokes Cby binding to CRM1 while inhibiting its interaction with the nuclear import receptor importin-α, thereby promoting cytoplasmic compartmentalization of Cby at steady state. Importantly, the NLS- and NES-dependent shuttling of Cby modulates the dynamic intracellular localization of β-catenin. In support of our model, short hairpin RNA–mediated knockdown of endogenous Cby results in nuclear accumulation of β-catenin. Taken together, these findings unravel the molecular basis through which a combinatorial action of Cby and 14-3-3 proteins controls the dynamic nuclear-cytoplasmic trafficking of β-catenin.

scholarly journals Suppressor of Fused Chaperones Gli Proteins To Generate Transcriptional Responses to Sonic Hedgehog Signaling

2016 ◽  
Vol 37 (3) ◽  
Author(s):  
Ziyu Zhang ◽  
Longyan Shen ◽  
Kelvin Law ◽  
Zengdi Zhang ◽  
Xiaotong Liu ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Nuclear Export ◽  
Hedgehog Signaling ◽  
Glycogen Synthase ◽  
Nuclear Export Signal ◽  
Transcriptional Responses ◽  
Content Type ◽  
Suppressor Of Fused ◽  
Gli Proteins ◽  
And Function

ABSTRACT Cellular responses to the graded Sonic Hedgehog (Shh) morphogenic signal are orchestrated by three Gli genes that give rise to both transcription activators and repressors. An essential downstream regulator of the pathway, encoded by the tumor suppressor gene Suppressor of fused (Sufu), plays critical roles in the production, trafficking, and function of Gli proteins, but the mechanism remains controversial. Here, we show that Sufu is upregulated in active Shh responding tissues and accompanies Gli activators translocating into and Gli repressors out of the nucleus. Trafficking of Sufu to the primary cilium, potentiated by Gli activators but not repressors, was found to be coupled to its nuclear import. We have identified a nuclear export signal (NES) motif of Sufu in juxtaposition to the protein kinase A (PKA) and glycogen synthase kinase 3 (GSK3) dual phosphorylation sites and show that Sufu binds the chromatin with both Gli1 and Gli3. Close comparison of neural tube development among individual Ptch1−/−, Sufu−/−, and Ptch1−/−; Sufu−/− double mutant embryos indicates that Sufu is critical for the maximal activation of Shh signaling essential to the specification of the most-ventral neurons. These data define Sufu as a novel class of molecular chaperone required for every aspect of Gli regulation and function.

scholarly journals Ciliary Hedgehog signaling regulates cell survival to build the facial midline

2021 ◽  
Author(s):  
Shaun R Abrams ◽  
Jeremy F Reiter
Keyword(s):  
Cell Death ◽  
Hedgehog Signaling ◽  
Gene Dosage ◽  
Negative Regulator ◽  
Cellular Survival ◽  
Pathway Activation ◽  
Prechordal Plate ◽  
Facial Midline ◽  
Hh Signaling ◽  
Craniofacial Defects

Craniofacial defects are among the most common phenotypes caused by ciliopathies, yet the developmental and molecular etiology of these defects is poorly understood. We investigated multiple mouse models of human ciliopathies (including Tctn2, Cc2d2a and Tmem231 mutants) and discovered that each displays hypotelorism, a narrowing of the midface. As early in development as the end of gastrulation, Tctn2 mutants displayed reduced activation of the Hedgehog (HH) pathway in the prechordal plate, the head organizer. This prechordal plate defect preceded a reduction of HH pathway activation and Shh expression in the adjacent neurectoderm. Concomitant with the reduction of HH pathway activity, Tctn2 mutants exhibited increased cell death in the neurectoderm and facial ectoderm, culminating in a collapse of the facial midline. Enhancing HH signaling by decreasing the gene dosage of a negative regulator of the pathway, Ptch1, decreased cell death and rescued the midface defect in both Tctn2 and Cc2d2a mutants. These results reveal that ciliary HH signaling mediates communication between the prechordal plate and the neurectoderm to provide cellular survival cues essential for development of the facial midline.

scholarly journals Keap1 Regulates the Oxidation-Sensitive Shuttling of Nrf2 into and out of the Nucleus via a Crm1-Dependent Nuclear Export Mechanism

2005 ◽  
Vol 25 (11) ◽  
pp. 4501-4513 ◽  
Author(s):  
Michaella Velichkova ◽  
Tama Hasson
Keyword(s):  
Nuclear Export ◽  
Consensus Sequence ◽  
Nuclear Export Signal ◽  
Antioxidant Response ◽  
Negative Regulator ◽  
Nuclear Accumulation ◽  
Leptomycin B ◽  
Hydrophobic Amino Acids ◽  
Export Signal ◽  
Full Activation

ABSTRACT Keap1 is a negative regulator of Nrf2, a transcription factor essential for antioxidant response element (ARE)-mediated gene expression. We find that Keap1 sequesters Nrf2 in the cytoplasm, not by docking it to the actin cytoskeleton but instead through an active Crm1/exportin-dependent nuclear export mechanism. Deletion and mutagenesis studies identified a nuclear export signal (NES) in the intervening region of Keap1 comprised of hydrophobic leucine and isoleucine residues in agreement with a traditional NES consensus sequence. Mutation of the hydrophobic amino acids resulted in nuclear accumulation of both Keap1 and Nrf2, as did treatment with the drug leptomycin B, which inactivates Crm1/exportin. ARE genes were partially activated under these conditions, suggesting that additional oxidation-sensitive elements are required for full activation of the antioxidant response. Based on these data, we propose a new model for regulation of Nrf2 by Keap1. Under normal conditions, Keap1 and Nrf2 are complexed in the cytoplasm where they are targeted for degradation. Oxidative stress inactivates Keap1's NES, allowing entry of both Keap1 and Nrf2 into the nucleus and transcriptional transactivation of ARE genes.

scholarly journals Ciliary Hedgehog signaling regulates cell survival to build the facial midline

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Shaun Abrams ◽  
Jeremy F Reiter
Keyword(s):  
Cell Death ◽  
Hedgehog Signaling ◽  
Gene Dosage ◽  
Negative Regulator ◽  
Cellular Survival ◽  
Pathway Activation ◽  
Prechordal Plate ◽  
Facial Midline ◽  
Hh Signaling ◽  
Craniofacial Defects

Craniofacial defects are among the most common phenotypes caused by ciliopathies, yet the developmental and molecular etiology of these defects is poorly understood. We investigated multiple mouse models of human ciliopathies (including Tctn2, Cc2d2a and Tmem231 mutants) and discovered that each displays hypotelorism, a narrowing of the midface. As early in development as the end of gastrulation, Tctn2 mutants displayed reduced activation of the Hedgehog (HH) pathway in the prechordal plate, the head organizer. This prechordal plate defect preceded a reduction of HH pathway activation and Shh expression in the adjacent neurectoderm. Concomitant with the reduction of HH pathway activity, Tctn2 mutants exhibited increased cell death in the neurectoderm and facial ectoderm, culminating in a collapse of the facial midline. Enhancing HH signaling by decreasing the gene dosage of a negative regulator of the pathway, Ptch1, decreased cell death and rescued the midface defect in both Tctn2 and Cc2d2a mutants. These results reveal that ciliary HH signaling mediates communication between the prechordal plate and the neurectoderm to provide cellular survival cues essential for development of the facial midline.

scholarly journals A mechanism for vertebrate Hedgehog signaling: recruitment to cilia and dissociation of SuFu–Gli protein complexes

2010 ◽  
Vol 191 (2) ◽  
pp. 415-428 ◽  
Author(s):  
Hanna Tukachinsky ◽  
Lyle V. Lopez ◽  
Adrian Salic
Keyword(s):  
Hedgehog Signaling ◽  
Primary Cilia ◽  
Protein Complexes ◽  
Transcription Activation ◽  
Cytoplasmic Protein ◽  
Suppressor Of Fused ◽  
Gli Proteins ◽  
Hh Signaling ◽  
Ciliary Localization ◽  
Kinase A

In vertebrates, Hedgehog (Hh) signaling initiated in primary cilia activates the membrane protein Smoothened (Smo) and leads to activation of Gli proteins, the transcriptional effectors of the pathway. In the absence of signaling, Gli proteins are inhibited by the cytoplasmic protein Suppressor of Fused (SuFu). It is unclear how Hh activates Gli and whether it directly regulates SuFu. We find that Hh stimulation quickly recruits endogenous SuFu–Gli complexes to cilia, suggesting a model in which Smo activates Gli by relieving inhibition by SuFu. In support of this model, we find that Hh causes rapid dissociation of the SuFu–Gli complex, thus allowing Gli to enter the nucleus and activate transcription. Activation of protein kinase A (PKA), an inhibitor of Hh signaling, blocks ciliary localization of SuFu–Gli complexes, which in turn prevents their dissociation by signaling. Our results support a simple mechanism in which Hh signals at vertebrate cilia cause dissociation of inactive SuFu–Gli complexes, a process inhibited by PKA.

scholarly journals Sonic hedgehog negatively regulates pre-TCR–induced differentiation by a Gli2-dependent mechanism

Blood ◽  
2009 ◽  
Vol 113 (21) ◽  
pp. 5144-5156 ◽  
Author(s):  
Nicola J. Rowbotham ◽  
Ariadne L. Hager-Theodorides ◽  
Anna L. Furmanski ◽  
Susan E. Ross ◽  
Susan V. Outram ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Negative Regulator ◽  
Double Positive ◽  
Induced Differentiation ◽  
Transgenic Expression ◽  
Tcr Signal Transduction ◽  
Hh Signaling ◽  
Dependent Mechanism

Abstract Hedgehog signaling regulates differentiation, survival, and proliferation of the earliest double-negative (DN) thymocytes, but its importance at later stages of T-cell development is controversial. Here we use loss- and gain-of-function mouse models to show that Shh, by signaling directly to the developing thymocyte, is a negative regulator of pre-TCR–induced differentiation from DN to double-positive (DP) cell. When hedgehog signaling was reduced, in the Shh−/− and Gli2−/− thymus, or by T lineage–specific transgenic expression of a transcriptional-repressor form of Gli2 (Gli2ΔC2), differentiation to DP cell after pre-TCR signal transduction was increased. In contrast, when Hh signaling was constitutively activated in thymocytes, by transgenic expression of a constitutive transcriptional-activator form of Gli2 (Gli2ΔN2), the production of DP cells was decreased. Gene expression profiling showed that physiologic Hh signaling in thymocytes maintains expression of the transcription factor FoxA2 on pre-TCR signal transduction.

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.

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