scholarly journals The Linker Histone H1.2 Is an Intermediate in the Apoptotic Response to Cytokine Deprivation in T-Effectors

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Megha Garg ◽  
Lakshmi R. Perumalsamy ◽  
G. V. Shivashankar ◽  
Apurva Sarin
Keyword(s):  
Nuclear Export ◽  
Linker Histone ◽  
Tissue Homeostasis ◽  
Trophic Factors ◽  
Apoptotic Response ◽  
Leptomycin B ◽  
Apoptotic Pathway ◽  
Extracellular Milieu ◽  
Cytokine Deprivation ◽  
Apoptotic Cascade

Tissue homeostasis is a dynamic process involving proliferation and the removal of redundant or damaged cells. This is exemplified in the coordinated deletion—triggered by limiting trophic factors/cytokines in the extracellular milieu—of differentiated T cells overproduced during the mammalian immune response. However, mechanisms by which extracellular cues are perceived and transduced as apoptotic triggers remain incompletely understood. T-effectors are dependent on cytokines for survival and undergo apoptosis following cytokine withdrawal. Here we report that leptomycin B (LMB), an inhibitor of nuclear export machinery, protected T-effectors from apoptosis implicating a nuclear intermediate in the apoptotic pathway. Evidence is presented that the linker histone H1.2 localizes to the cytoplasm, by a mechanism sensitive to regulation by LMB, to activate apoptotic signaling culminating in nuclear and mitochondrial damage in T-effectors in response to cytokine deprivation. H1.2 is detected in a complex with the proapoptotic mitochondrial resident Bak and its subcellular localization regulated by Jun-N-terminal kinase (JNK), an intermediate in the apoptotic cascade in T-effectors. These data suggest that metabolic stressors may impinge on H1.2 dynamics favoring its activity at the mitochondrion, thereby functioning as a molecular switch for T-effector apoptosis.

A global survey of CRM1-dependent nuclear export sequences in the human deubiquitinase family

2011 ◽  
Vol 441 (1) ◽  
pp. 209-217 ◽  
Author(s):  
Iraia García-Santisteban ◽  
Sonia Bañuelos ◽  
Jose A. Rodríguez
Keyword(s):  
Nuclear Export ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Site Directed Mutagenesis ◽  
The Novel ◽  
Sequence Motifs ◽  
Leptomycin B ◽  
Specific Amino Acid ◽  
Green Fluorescent ◽  
Nuclear Export Receptor

The mechanisms that regulate the nucleocytoplasmic localization of human deubiquitinases remain largely unknown. The nuclear export receptor CRM1 binds to specific amino acid motifs termed NESs (nuclear export sequences). By using in silico prediction and experimental validation of candidate sequences, we identified 32 active NESs and 78 inactive NES-like motifs in human deubiquitinases. These results allowed us to evaluate the performance of three programs widely used for NES prediction, and to add novel information to the recently redefined NES consensus. The novel NESs identified in the present study reveal a subset of 22 deubiquitinases bearing motifs that might mediate their binding to CRM1. We tested the effect of the CRM1 inhibitor LMB (leptomycin B) on the localization of YFP (yellow fluorescent protein)- or GFP (green fluorescent protein)-tagged versions of six NES-bearing deubiquitinases [USP (ubiquitin-specific peptidase) 1, USP3, USP7, USP21, CYLD (cylindromatosis) and OTUD7B (OTU-domain-containing 7B)]. YFP–USP21 and, to a lesser extent, GFP–OTUD7B relocated from the cytoplasm to the nucleus in the presence of LMB, revealing their nucleocytoplasmic shuttling capability. Two sequence motifs in USP21 had been identified during our survey as active NESs in the export assay. Using site-directed mutagenesis, we show that one of these motifs mediates USP21 nuclear export, whereas the second motif is not functional in the context of full-length USP21.

scholarly journals Effects on normal fibroblasts and neuroblastoma cells of the activation of the p53 response by the nuclear export inhibitor leptomycin B

Oncogene ◽  
1999 ◽  
Vol 18 (51) ◽  
pp. 7378-7386 ◽  
Author(s):  
Philip Smart ◽  
E Birgitte Lane ◽  
David P Lane ◽  
Carol Midgley ◽  
Borek Vojtesek ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Neuroblastoma Cells ◽  
Leptomycin B ◽  
P53 Response

scholarly journals Disruption of Mcl-1·Bim Complex in Granzyme B-mediated Mitochondrial Apoptosis

2005 ◽  
Vol 280 (16) ◽  
pp. 16383-16392 ◽  
Author(s):  
Jie Han ◽  
Leslie A. Goldstein ◽  
Brian R. Gastman ◽  
Asaf Rabinovitz ◽  
Hannah Rabinowich
Keyword(s):  
Granzyme B ◽  
Biological Significance ◽  
Carcinoma Cells ◽  
Cleavage Sites ◽  
Apoptotic Pathway ◽  
Terminal Fragment ◽  
Subsequent Degradation ◽  
Interfering Rna ◽  
Cytotoxic Mechanism ◽  
Apoptotic Cascade

Recently, we reported the identification of a novel mitochondrial apoptotic pathway for granzyme B (GrB) (Han, J., Goldstein, L. A., Gastman, B. R., Froelich, C. J., Yin, X. M., and Rabinowich, H. (2004)J. Biol. Chem.279, 22020–22029). The newly identified GrB-mediated mitochondrial cascade was initiated by the cleavage and subsequent degradation of Mcl-1, resulting in the release of mitochondrial Bim from Mcl-1 sequestration. To investigate the biological significance of Mcl-1 cleavage by GrB, we mapped the major GrB cleavage sites and evaluated the apoptotic potential of the cleavage products. GrB cleaves Mcl-1 after aspartic acid residues 117, 127, and 157, generating C-terminal fragments that all contain BH-1, BH-2, BH-3, and transmembrane domains. These fragments accumulate at an early apoptotic phase but are eliminated by further degradation during the apoptotic process. The major Mcl-1 C-terminal fragment generated by GrB (residues 118–350) was unable to induce or enhance apoptosis when transfected into tumor cells. Instead, this Mcl-1 C-terminal fragment maintained a partial protective capability against GrB-mediated apoptosis via its lower affinity to Bim. In comparison with ectopically expressed full-length Mcl-1, the stably transfected C-terminal fragments of Mcl-1 were less efficiently localized to the mitochondria. Knockdown of Mcl-1, as achieved by transfection with Mcl-1-specific short interfering RNA, resulted in a significant level of apoptosis in the absence of external apoptotic stimulation and, in addition, enhanced the susceptibility of breast carcinoma cells to GrB cytotoxicity. The significance of Bim in this GrB apoptotic cascade was indicated by the marked protection against GrB-mediated apoptosis endowed on these cells through Bim knockdown. Our studies suggest that the disruption of the Mcl-1·Bim complex by GrB initiates a major Bim-mediated cellular cytotoxic mechanism that requires the elimination of Mcl-1 following its initial cleavage.

Developmentally regulated activity of CRM1/XPO1 during early Xenopus embryogenesis

2000 ◽  
Vol 113 (3) ◽  
pp. 451-459 ◽  
Author(s):  
M. Callanan ◽  
N. Kudo ◽  
S. Gout ◽  
M. Brocard ◽  
M. Yoshida ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Fluorescent Protein ◽  
Intracellular Localization ◽  
Nuclear Export Signal ◽  
Specific Inhibitor ◽  
Amino Acid Identity ◽  
Early Embryogenesis ◽  
Leptomycin B ◽  
Developmentally Regulated ◽  
Neurula Stage

In this work, we have investigated the role of CRM1/XPO1, a protein involved in specific export of proteins and RNA from the nucleus, in early Xenopus embryogenesis. The cloning of the Xenopus laevis CRM1, XCRM1, revealed remarkable conservation of the protein during evolution (96.7% amino acid identity between Xenopus and human). The protein and mRNA are maternally expressed and are present during early embryogenesis. However, our data show that the activity of the protein is developmentally regulated. Embryonic development is insensitive to leptomycin B, a specific inhibitor of CRM1, until the neurula stage. Moreover, the nuclear localization of CRM1 changes concomitantly with the appearance of the leptomycin B sensitivity. These data suggest that CRM1, present initially in an inactive form, becomes functional before the initiation of the neurula stage during gastrula-neurula transition, a period known to correspond to a critical transition in the pattern of gene expression. Finally, we confirmed the gastrula-neurula transition-dependent activation of CRM1 by pull-down experiments as well as by the study of the intracellular localization of a green fluorescent protein tagged with a nuclear export signal motif during early development. This work showed that the regulated activity of CRM1 controls specific transitions during normal development and thus might be a key regulator of early embryogenesis.

scholarly journals HP1γ Sensitizes Cervical Cancer Cells to Cisplatin through the Suppression of UBE2L3

2020 ◽  
Vol 21 (17) ◽  
pp. 5976 ◽  
Author(s):  
Sang Ah Yi ◽  
Go Woon Kim ◽  
Jung Yoo ◽  
Jeung-Whan Han ◽  
So Hee Kwon
Keyword(s):  
Cervical Cancer ◽  
Cancer Cells ◽  
Nuclear Export ◽  
Nuclear Translocation ◽  
Leptomycin B ◽  
P53 Signaling ◽  
Cervical Cancer Cells ◽  
Ubiquitin Conjugating Enzyme ◽  
The Stability

Cisplatin is the most frequently used agent for chemotherapy against cervical cancer. However, recurrent use of cisplatin induces resistance, representing a major hurdle in the treatment of cervical cancer. Our previous study revealed that HP1γ suppresses UBE2L3, an E2 ubiquitin conjugating enzyme, thereby enhancing the stability of tumor suppressor p53 specifically in cervical cancer cells. As a follow-up study of our previous findings, here we have identified that the pharmacological substances, leptomycin B and doxorubicin, can improve the sensitivity of cervical cancer cells to cisplatin inducing HP1γ-mediated elevation of p53. Leptomycin B, which inhibits the nuclear export of HP1γ, increased cisplatin-dependent apoptosis induction by promoting the activation of p53 signaling. We also found that doxorubicin, which induces the DNA damage response, promotes HP1γ-mediated silencing of UBE2L3 and increases p53 stability. These effects resulted from the nuclear translocation and binding of HP1γ on the UBE2L3 promoter. Doxorubicin sensitized the cisplatin-resistant cervical cancer cells, enhancing their p53 levels and rate of apoptosis when administered together with cisplatin. Our findings reveal a therapeutic strategy to target a specific molecular pathway that contributes to p53 degradation for the treatment of patients with cervical cancer, particularly with cisplatin resistance.

scholarly journals Leptomycin B, an Inhibitor of the Nuclear Export Receptor CRM1, Inhibits COX-2 Expression

2002 ◽  
Vol 278 (5) ◽  
pp. 2773-2776 ◽  
Author(s):  
Byeong-Churl Jang ◽  
Ursula Muñoz-Najar ◽  
Ji-Hye Paik ◽  
Kevin Claffey ◽  
Minoru Yoshida ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Leptomycin B ◽  
Cox 2 ◽  
Nuclear Export Receptor

scholarly journals Exportin 1 Mediates Nuclear Export of the Kinetoplastid Spliced Leader RNA

2003 ◽  
Vol 2 (2) ◽  
pp. 222-230 ◽  
Author(s):  
Gusti M. Zeiner ◽  
Nancy R. Sturm ◽  
David A. Campbell
Keyword(s):  
Nuclear Export ◽  
Ectopic Expression ◽  
Specific Inhibitor ◽  
Leptomycin B ◽  
Spliced Leader ◽  
Small Nuclear Rnas ◽  
Rna Biogenesis ◽  
Common Substrate ◽  
The Common

ABSTRACT The kinetoplastid protozoan spliced leader (SL) RNA is the common substrate pre-mRNA utilized in all trans-splicing reactions. Here we show by fluorescence in situ hybridization that the SL RNA is present in the cytoplasm of Leishmania tarentolae and Trypanosoma brucei. Treatment with the karyopherin-specific inhibitor leptomycin B was toxic to T. brucei and eliminated the cytoplasmic SL RNA, suggesting that cytoplasmic SL RNA was dependent on the nuclear exporter exportin 1 (XPO1). Ectopic expression of xpo1 with a C506S mutation in T. brucei conferred resistance to leptomycin B. A reduction in SL RNA 3′ extension removal and 5′ methylation of nucleotide U4 was observed in wild-type T. brucei treated with leptomycin B, suggesting that the cytoplasmic stage is necessary for SL RNA biogenesis. This study demonstrates spatial and mechanistic similarities between the posttranscriptional trafficking of the kinetoplastid protozoan SL RNA and the metazoan cis-spliceosomal small nuclear RNAs.

scholarly journals Vaccinia Virus Infection Disarms the Mitochondrion-Mediated Pathway of the Apoptotic Cascade by Modulating the Permeability Transition Pore

2001 ◽  
Vol 75 (23) ◽  
pp. 11437-11448 ◽  
Author(s):  
Shawn T. Wasilenko ◽  
Adrienne F. A. Meyers ◽  
Kathleen Vander Helm ◽  
Michele Barry
Keyword(s):  
Virus Infection ◽  
Vaccinia Virus ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Jurkat Cells ◽  
Caspase 8 ◽  
Apoptotic Pathway ◽  
Vaccinia Virus Infection ◽  
Infected Cells ◽  
Apoptotic Cascade

ABSTRACT Many viruses have evolved strategies that target crucial components within the apoptotic cascade. One of the best studied is the caspase 8 inhibitor, crmA/Spi-2, encoded by members of the poxvirus family. Since many proapoptotic stimuli induce apoptosis through a mitochondrion-dependent, caspase 8-independent pathway, we hypothesized that vaccinia virus would encode a mechanism to directly modulate the mitochondrial apoptotic pathway. In support of this, we observed that Jurkat cells, which undergo Fas-mediated apoptosis exclusively through the mitochondrial route, were resistant to Fas-induced death following infection with a crmA/Spi-2-deficient strain of vaccinia virus. In addition, vaccinia virus-infected cells subjected to the proapoptotic stimulus staurosporine exhibited decreased levels of both cytochromec released from the mitochondria and caspase 3 activation. In all cases we found that the loss of the mitochondrial membrane potential, which occurs as a result of opening the multimeric permeability transition pore complex, was prevented in vaccinia virus-infected cells. Moreover, vaccinia virus infection specifically inhibited opening of the permeability transition pore following treatment with the permeability transition pore ligand atractyloside and t-butylhydroperoxide. These studies indicate that vaccinia virus infection directly impacts the mitochondrial apoptotic cascade by influencing the permeability transition pore.

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