1
|
Staniek J, Rizzi M. Signaling Activation and Modulation in Extrafollicular B Cell Responses. Immunol Rev 2025; 330:e70004. [PMID: 39917832 PMCID: PMC11803499 DOI: 10.1111/imr.70004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2024] [Accepted: 01/20/2025] [Indexed: 02/11/2025]
Abstract
The differentiation of naive follicular B cells into either the germinal center (GC) or extrafollicular (EF) pathway plays a critical role in shaping the type, affinity, and longevity of effector B cells. This choice also governs the selection and survival of autoreactive B cells, influencing their potential to enter the memory compartment. During the first 2-3 days following antigen encounter, initially activated B cells integrate activating signals from T cells, Toll-like receptors (TLRs), and cytokines, alongside inhibitory signals mediated by inhibitory receptors. This integration modulates the intensity of signaling, particularly of the PI3K/AKT/mTOR pathway, which plays a central role in guiding developmental decisions. These early signaling events determine whether B cells undergo GC maturation or differentiate rapidly into antibody-secreting cells (ASCs) via the EF pathway. Dysregulation of these signaling pathways-whether through excessive activation or defective regulatory mechanisms-can disrupt the balance between GC and EF fates, predisposing individuals to autoimmunity. Accordingly, aberrant PI3K/AKT/mTOR signaling has been implicated in the defective selection of autoreactive B cells, increasing the risk of autoimmune disease. This review focuses on the signaling events in newly activated B cells, with an emphasis on the induction and regulation of the PI3K/AKT/mTOR pathway. It also highlights gaps in our understanding of how alternative B cell fates are regulated. Both the physiological context and the implications of inborn errors of immunity (IEIs) and complex autoimmune conditions will be discussed in this regard.
Collapse
Affiliation(s)
- Julian Staniek
- Department of Rheumatology and Clinical Immunology, Faculty of Medicine, University Medical Center FreiburgUniversity of FreiburgFreiburgGermany
- Faculty of Medicine, Center for Chronic Immunodeficiency, University Medical Center FreiburgUniversity of FreiburgFreiburgGermany
| | - Marta Rizzi
- Department of Rheumatology and Clinical Immunology, Faculty of Medicine, University Medical Center FreiburgUniversity of FreiburgFreiburgGermany
- Faculty of Medicine, Center for Chronic Immunodeficiency, University Medical Center FreiburgUniversity of FreiburgFreiburgGermany
- Division of Clinical and Experimental Immunology, Institute of Immunology, Center for Pathophysiology, Infectiology and ImmunologyMedical University of ViennaViennaAustria
- CIBSS—Centre for Integrative Biological Signalling StudiesUniversity of FreiburgFreiburgGermany
| |
Collapse
|
2
|
Mahmud I, Liao D. DAXX in cancer: phenomena, processes, mechanisms and regulation. Nucleic Acids Res 2019; 47:7734-7752. [PMID: 31350900 PMCID: PMC6735914 DOI: 10.1093/nar/gkz634] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 12/13/2022] Open
Abstract
DAXX displays complex biological functions. Remarkably, DAXX overexpression is a common feature in diverse cancers, which correlates with tumorigenesis, disease progression and treatment resistance. Structurally, DAXX is modular with an N-terminal helical bundle, a docking site for many DAXX interactors (e.g. p53 and ATRX). DAXX's central region folds with the H3.3/H4 dimer, providing a H3.3-specific chaperoning function. DAXX has two functionally critical SUMO-interacting motifs. These modules are connected by disordered regions. DAXX's structural features provide a framework for deciphering how DAXX mechanistically imparts its functions and how its activity is regulated. DAXX modulates transcription through binding to transcription factors, epigenetic modifiers, and chromatin remodelers. DAXX's localization in the PML nuclear bodies also plays roles in transcriptional regulation. DAXX-regulated genes are likely important effectors of its biological functions. Deposition of H3.3 and its interactions with epigenetic modifiers are likely key events for DAXX to regulate transcription, DNA repair, and viral infection. Interactions between DAXX and its partners directly impact apoptosis and cell signaling. DAXX's activity is regulated by posttranslational modifications and ubiquitin-dependent degradation. Notably, the tumor suppressor SPOP promotes DAXX degradation in phase-separated droplets. We summarize here our current understanding of DAXX's complex functions with a focus on how it promotes oncogenesis.
Collapse
Affiliation(s)
- Iqbal Mahmud
- Department of Anatomy and Cell Biology, UF Health Cancer Center, University of Florida College of Medicine, 1333 Center Drive, Gainesville, FL 32610-0235, USA
| | - Daiqing Liao
- Department of Anatomy and Cell Biology, UF Health Cancer Center, University of Florida College of Medicine, 1333 Center Drive, Gainesville, FL 32610-0235, USA
| |
Collapse
|
3
|
Hathaway-Schrader JD, Doonan BP, Hossain A, Radwan FFY, Zhang L, Haque A. Autophagy-dependent crosstalk between GILT and PAX-3 influences radiation sensitivity of human melanoma cells. J Cell Biochem 2017; 119:2212-2221. [PMID: 28857256 DOI: 10.1002/jcb.26383] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 08/23/2017] [Indexed: 01/19/2023]
Abstract
Melanoma represents an ever-increasing problem in the western world as incidence rates continue to climb. Though manageable during early stages, late stage metastatic disease is highly resistant to current intervention. We have previously shown that gamma-interferon-inducible lysosomal thiol-reductase (GILT) enhances HLA class II antigen processing and immune detection of human melanoma cells. Here we report that GILT expression inhibits a potential target, paired box-3 (PAX-3) protein, in late stage human metastatic melanoma. We also show that GILT transfection or induction by IFN-γ, decreases PAX-3 protein expression while upregulating the expression of Daxx, which is also a repressor of PAX-3. Confocal microscopic analysis demonstrated that GILT co-localizes with PAX-3 protein, but not with Daxx within melanoma cells. Immunoprecipitation and immunoblotting studies suggest that GILT expression negatively regulates PAX-3 through the autophagy pathway, potentially resulting in increased susceptibility to conventional treatment in the form of chemotherapy or radiotherapy. While high-dose radiation is a common treatment for melanoma patients, our data suggest that GILT expression significantly increased the susceptibility of melanoma cells to low-dose radiation therapy via upregulation of tumor suppressor protein p53. Overall, these data suggest that GILT has multiple roles in inducing human melanoma cells as better targets for radiation and immunotherapy.
Collapse
Affiliation(s)
- Jessica D Hathaway-Schrader
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| | - Bently P Doonan
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| | - Azim Hossain
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| | - Faisal F Y Radwan
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| | - Lixia Zhang
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| | - Azizul Haque
- Department of Microbiology and Immunology, Hollings Cancer Center, and Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina
| |
Collapse
|
4
|
Coronel R, Jesus DM, Dalle Ore L, Mymryk JS, Hertel L. Activation of Langerhans-Type Dendritic Cells Alters Human Cytomegalovirus Infection and Reactivation in a Stimulus-Dependent Manner. Front Microbiol 2016; 7:1445. [PMID: 27683575 PMCID: PMC5021960 DOI: 10.3389/fmicb.2016.01445] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 08/30/2016] [Indexed: 12/18/2022] Open
Abstract
Oral mucosal Langerhans cells (LC) are likely to play important roles in host defense against infection by human cytomegalovirus (CMV). We previously showed that in vitro-differentiated immature LC (iLC) populations contain smaller amounts of infected cells but produce higher yields than mature LC (mLC) cultures, obtained by iLC stimulation with fetal bovine serum (FBS), CD40 ligand (CD40L) and lipopolysaccharide (LPS). Here, we sought to determine if exposure to select stimuli can improve LC permissiveness to infection, if specific components of the mLC cocktail are responsible for lowering viral yields, if this is due to defects in progeny production or release, and if these restrictions are also effective against reactivated virus. None of the stimuli tested extended the proportion of infected cells to 100%, suggesting that the block to infection onset cannot be fully removed. While CD40L and FBS exerted positive effects on viral progeny production per cell, stimulation with LPS alone or in combination with CD40L was detrimental. Reductions in viral titers were not due to defects in progeny release, and the permissive or restrictive intracellular environment established upon exposure to each stimulus appeared to act in a somewhat similar way toward lytic and latent infections.
Collapse
Affiliation(s)
- Roxanne Coronel
- Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute Oakland, CA, USA
| | - Desyree M Jesus
- Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute Oakland, CA, USA
| | - Lucia Dalle Ore
- Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute Oakland, CA, USA
| | - Joe S Mymryk
- Department of Microbiology and Immunology and Department of Oncology, The University of Western Ontario London, ON, Canada
| | - Laura Hertel
- Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute Oakland, CA, USA
| |
Collapse
|
5
|
Age-dependent differential expression of death-associated protein 6 (Daxx) in various peripheral tissues and different brain regions of C57BL/6 male mice. Biogerontology 2016; 17:817-828. [PMID: 27465500 DOI: 10.1007/s10522-016-9651-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 05/17/2016] [Indexed: 12/17/2022]
Abstract
Death-associated protein 6 (DAXX) is a ubiquitous protein implicated in various cellular processes such as apoptosis, tumorigenesis, development and transcription. The role of DAXX is however ambiguous and many contradictory results regarding its function in apoptosis upon various cellular stresses are described in the literature. In order to have a better understanding of the role of DAXX throughout the entire organism under physiological stress conditions, we have characterized the mRNA levels, protein expression and the proteolytic processing of DAXX in the normal aging process in peripheral organs and brain regions in C57BL/6 male mice. Overall, Daxx mRNA expression decreases with aging in the liver, kidney, heart, cortex and cerebellum. In contrast, an increase is observed in the striatum. The protein expression of DAXX and of its proteolytic fragments increases with aging in the kidney, heart and cortex. In liver and spleen, no changes are observed while in the striatum and cerebellum, certain forms increase and others decrease with age, suggesting that the functions of DAXX may be cell type dependent. This study provides important details regarding the expression and post-translational modifications of DAXX in aging in the entire organism and provides reference data for the deregulation observed in age-associated diseases.
Collapse
|
6
|
Sorrentino G, Comel A, Mantovani F, Del Sal G. Regulation of mitochondrial apoptosis by Pin1 in cancer and neurodegeneration. Mitochondrion 2014; 19 Pt A:88-96. [PMID: 25132079 DOI: 10.1016/j.mito.2014.08.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/08/2014] [Accepted: 08/11/2014] [Indexed: 11/15/2022]
Abstract
Mitochondria are sensitive and efficient organelles that regulate essential biological processes including: energy metabolism, decoding and transduction of intracellular signals, and balance between cell death and survival. Of note, dysfunctions in mitochondrial physiology are a general hallmark of cancer cells, leading to transformation-related features such as altered cellular metabolism, survival under stress conditions and reduced apoptotic response to chemotherapy. Mitochondrial apoptosis is a finely regulated process that derives from activation of multiple signaling networks. A crucial biochemical requirement for transducing pro-apoptotic stimuli is represented by kinase-dependent phosphorylation cascades. In this context a pivotal role is played by the prolyl-isomerase Pin1, which translates Ser/Thr-Pro phosphorylation into conformational changes able to modify the activities of its substrates. In this review we will discuss the impact of Pin1 in regulating various aspects of apoptosis in different biological contexts with particular emphasis on cancer and neurodegenerative diseases.
Collapse
Affiliation(s)
- Giovanni Sorrentino
- Laboratorio Nazionale CIB Area Science Park, Trieste Italy; Dipartimento di Scienze della Vita Università degli Studi di Trieste- Trieste Italy
| | - Anna Comel
- Laboratorio Nazionale CIB Area Science Park, Trieste Italy; Dipartimento di Scienze della Vita Università degli Studi di Trieste- Trieste Italy
| | - Fiamma Mantovani
- Laboratorio Nazionale CIB Area Science Park, Trieste Italy; Dipartimento di Scienze della Vita Università degli Studi di Trieste- Trieste Italy
| | - Giannino Del Sal
- Laboratorio Nazionale CIB Area Science Park, Trieste Italy; Dipartimento di Scienze della Vita Università degli Studi di Trieste- Trieste Italy.
| |
Collapse
|
7
|
Rivera-Molina YA, Martínez FP, Tang Q. Nuclear domain 10 of the viral aspect. World J Virol 2013; 2:110-122. [PMID: 24255882 PMCID: PMC3832855 DOI: 10.5501/wjv.v2.i3.110] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 05/31/2013] [Accepted: 07/11/2013] [Indexed: 02/05/2023] Open
Abstract
Nuclear domain 10 (ND10) are spherical bodies distributed throughout the nucleoplasm and measuring around 0.2-1.0 μm. First observed under an electron microscope, they were originally described as dense bodies found in the nucleus. They are known by a number of other names, including Promyelocytic Leukemia bodies (PML bodies), Kremer bodies, and PML oncogenic domains. ND10 are frequently associated with Cajal bodies and cleavage bodies. It has been suggested that they play a role in regulating gene transcription. ND10 were originally characterized using human autoantisera, which recognizes Speckled Protein of 100 kDa, from patients with primary biliary cirrhosis. At the immunohistochemical level, ND10 appear as nuclear punctate structures, with 10 indicating the approximate number of dots per nucleus observed. ND10 do not colocalize with kinetochores, centromeres, sites of mRNA processing, or chromosomes. Resistance of ND10 antigens to nuclease digestion and salt extraction suggest that ND10 are associated with the nuclear matrix. They are often identified by immunofluorescent assay using specific antibodies against PML, Death domain-associated protein, nuclear dot protein (NDP55), and so on. The role of ND10 has long been the subject of investigation, with the specific connection of ND10 and viral infection having been a particular focus for almost 20 years. This review summarizes the relationship of ND10 and viral infection. Some future study directions are also discussed.
Collapse
|
8
|
Muromoto R. Death Domain-associated Protein (DAXX)-mediated Regulation of Transcription and Cell Death. YAKUGAKU ZASSHI 2012; 132:979-84. [DOI: 10.1248/yakushi.132.979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Ryuta Muromoto
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University
| |
Collapse
|
9
|
Wethkamp N, Hanenberg H, Funke S, Suschek CV, Wetzel W, Heikaus S, Grinstein E, Ramp U, Engers R, Gabbert HE, Mahotka C. Daxx-beta and Daxx-gamma, two novel splice variants of the transcriptional co-repressor Daxx. J Biol Chem 2011; 286:19576-19588. [PMID: 21482821 PMCID: PMC3103337 DOI: 10.1074/jbc.m110.196311] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 03/26/2011] [Indexed: 12/15/2022] Open
Abstract
Daxx is involved in transcriptional control and apoptosis. It comprises several domains, including a regulatory C terminus that is responsible for the interaction with numerous proteins such as p53, promyelocytic leukemia protein (PML), and Hsp27. Here, we describe the identification and characterization of two novel variants of Daxx termed Daxx-β and Daxx-γ, which are generated by alternative splicing. Alternative splicing results in a truncated regulatory C terminus in both proteins. As a consequence, Daxx-β and Daxx-γ show a markedly decreased affinity to PML, which in turn is associated with a different subnuclear localization of these proteins compared with Daxx. Although Daxx is localized mainly in PML-oncogenic domains (PODs) Daxx-β and Daxx-γ display a distinct distribution pattern. Furthermore, Daxx-β and Daxx-γ show a decreased affinity to p53 also due to the truncated C terminus. We provide evidence that the p53 recruitment into PODs is Daxx isoform-dependent. The decreased affinity of Daxx-β/-γ to p53 and PML results in a diffuse localization of p53 throughout the nucleus. In contrast to Daxx, Daxx-β and Daxx-γ are unable to repress p53-mediated transcription. Therefore, alternative splicing of Daxx might indicate an additional level in the cellular apoptosis network.
Collapse
Affiliation(s)
- Nils Wethkamp
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Helmut Hanenberg
- the Department of Pediatrics, the Herman B. Wells Center for Pediatric Research, Indianapolis, Indiana 46202
- the Department of Otorhinolaryngology, Heinrich Heine University School of Medicine, D-40225 Düsseldorf, Germany, and
| | - Sarah Funke
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | | | - Wiebke Wetzel
- the Institute of Molecular Biology and Biochemistry II and
| | - Sebastian Heikaus
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Edgar Grinstein
- Department of Pediatric Oncology, Hematology, and Clinical Immunology, Center for Child and Adolescent Health, Heinrich Heine University Medical Faculty, D-40225 Düsseldorf, Germany
| | - Uwe Ramp
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Rainer Engers
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Helmut E. Gabbert
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Csaba Mahotka
- From the Institute of Pathology, Heinrich Heine University, University Hospital, Medical Faculty, D-40225 Düsseldorf, Germany
| |
Collapse
|
10
|
Muromoto R, Kuroda M, Togi S, Sekine Y, Nanbo A, Shimoda K, Oritani K, Matsuda T. Functional involvement of Daxx in gp130-mediated cell growth and survival in BaF3 cells. Eur J Immunol 2010; 40:3570-80. [PMID: 21108476 DOI: 10.1002/eji.201040688] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/02/2010] [Accepted: 09/02/2010] [Indexed: 01/05/2023]
Abstract
Death domain-associated protein (Daxx) is a multifunctional protein that modulates both cell death and transcription. Several recent studies have indicated that Daxx is a mediator of lymphocyte death and/or growth suppression, although the detailed mechanism is unclear. Previously, we reported that Daxx suppresses IL-6 family cytokine-induced gene expression by interacting with STAT3. STAT3 is important for the growth and survival of lymphocytes; therefore, we here examined the role of Daxx in the gp130/STAT3-dependent cell growth/survival signals. We found that Daxx suppresses the gp130/STAT3-dependent cell growth and that Daxx endogenously interacts with STAT3 and inhibits the DNA-binding activity of STAT3. Moreover, small-interfering RNA-mediated knockdown of Daxx enhanced the expression of STAT3-target genes and accelerated the STAT3-mediated cell cycle progression. In addition, knockdown of Daxx-attenuated lactate dehydrogenase leakage from cells, indicating that Daxx positively regulates cell death during gp130/STAT3-mediated cell proliferation. Notably, Daxx specifically suppressed the levels of Bcl2 mRNA and protein, even in cytokine-unstimulated cells, indicating that Daxx regulates Bcl2 expression independently of activated STAT3. These results suggest that Daxx suppresses gp130-mediated cell growth and survival by two independent mechanisms: inhibition of STAT3-induced transcription and down-regulation of Bcl2 expression.
Collapse
Affiliation(s)
- Ryuta Muromoto
- Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku, Sapporo, Japan
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Tower C, Fu L, Gill R, Prichard M, Lesort M, Sztul E. Human cytomegalovirus UL97 kinase prevents the deposition of mutant protein aggregates in cellular models of Huntington's disease and ataxia. Neurobiol Dis 2010; 41:11-22. [PMID: 20732421 DOI: 10.1016/j.nbd.2010.08.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 07/26/2010] [Accepted: 08/16/2010] [Indexed: 01/13/2023] Open
Abstract
The presence of aggregates of abnormally expanded polyglutamine (polyQ)-containing proteins are a pathological hallmark of a number of neurodegenerative diseases including Huntington's disease (HD) and spinocerebellar ataxia-3 (SCA3). Previous studies in cellular, Drosophila, and mouse models of HD and SCA have shown that neurodegeneration can be prevented by manipulations that inhibit polyQ aggregation. We have shown that the UL97 kinase of the human cytomegalovirus (HCMV) prevents aggregation of the pp71 and pp65 viral tegument proteins. To explore whether UL97 may act as a general antiaggregation factor, we examined whether UL97 prevents aggregation of cellular non-polyQ and polyQ proteins. We report that UL97 prevents the deposition of aggregates of two non-polyQ proteins: a protein chimera (GFP170*) composed of the green fluorescent protein and a fragment of the Golgi Complex protein (GCP-170) and a chimera composed of the red fluorescent protein (RFP) fused to the Werner syndrome protein (WRN), a RecQ helicase and exonuclease involved in DNA repair. Furthermore, we show that UL97 inhibits aggregate deposition in cellular models of HD and SCA3. UL97 prevents the deposition of aggregates of the mutant huntingtin exon 1 containing 82 glutamine repeats (HttExon1-Q82) or full length ataxin-3 containing a 72 polyQ track (AT3-72Q). The kinase activity of UL97 appears critical, as the kinase-dead UL97 mutant (K335M) fails to prevent aggregate formation. We further show that UL97 disrupts nuclear PML bodies and decreases p53-mediated transcription. The universality of the antiaggregation effect of UL97 suggests that UL97 targets a key cellular factor that regulates cellular aggregation mechanisms. Our results identify UL97 as a novel means to modulate polyQ aggregation and suggest that UL97 can serve as a novel tool to probe the cellular mechanisms that contribute to the formation of aggregates in polyglutamine disorders.
Collapse
Affiliation(s)
- Cristy Tower
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | | | | | | | | |
Collapse
|
12
|
Salomoni P, Ferguson BJ, Wyllie AH, Rich T. New insights into the role of PML in tumour suppression. Cell Res 2008; 18:622-40. [PMID: 18504460 DOI: 10.1038/cr.2008.58] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The PML gene is involved in the t(15;17) translocation of acute promyelocytic leukaemia (APL), which generates the oncogenic fusion protein PML (promyelocytic leukaemia protein)-retinoic acid receptor alpha. The PML protein localises to a subnuclear structure called the PML nuclear domain (PML-ND), of which PML is the essential structural component. In APL, PML-NDs are disrupted, thus implicating these structures in the pathogenesis of this leukaemia. Unexpectedly, recent studies indicate that PML and the PML-ND play a tumour suppressive role in several different types of human neoplasms in addition to APL. Because of PML's extreme versatility and involvement in multiple cellular pathways, understanding the mechanisms underlying its function, and therefore role in tumour suppression, has been a challenging task. In this review, we attempt to critically appraise the more recent advances in this field and propose new avenues of investigation.
Collapse
Affiliation(s)
- P Salomoni
- MRC Toxicology Unit, Lancaster Road Box 138, Leicester, LE 9HN, UK.
| | | | | | | |
Collapse
|
13
|
Leal-Sanchez J, Couzinet A, Rossin A, Abdel-Sater F, Chakrabandhu K, Luci C, Anjuere F, Stebe E, Hancock D, Hueber AO. Requirement for Daxx in mature T-cell proliferation and activation. Cell Death Differ 2006; 14:795-806. [PMID: 17082815 DOI: 10.1038/sj.cdd.4402056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The protein Daxx promotes Fas-mediated cell death through activation of apoptosis signal-regulating kinase 1, leading to the activation of the MAPKs JNK and p38. Owing to the in utero lethality of daxx-deficient mice, the in vivo role of Daxx has been so far difficult to analyze. We have generated transgenic mice expressing a dominant-negative form of Daxx (Daxx-DN) in the T-cell lineage. We show that Daxx is recruited to the Fas receptor upon FasL engagement and that Daxx-DN expression protects activated T cells from Fas-induced cell death, by preventing the death-inducing signal complex to be properly formed. Normal lymphocyte development and homeostasis are nevertheless observed. Interestingly, we report that both in vitro and in vivo stimulation of Daxx-DN T-lymphocytes leads to increased proliferative T-cell responses. This increased proliferation is associated with a marked increase in tyrosine phosphorylation of LAT and ZAP70 as Daxx-DN favor their recruitment to the T-cell receptor (TCR) complex. These findings identify Daxx as a critical regulator of T-lymphocyte homeostasis by decreasing TCR-induced cell proliferation and by promoting Fas-mediated cell death.
Collapse
Affiliation(s)
- J Leal-Sanchez
- Equipe Labellisée par La Ligue Nationale Centre le Cancer Institute of Signalling, Developmental Biology and Cancer Research, CNRS UMR 6543, Nice, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|