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Cota P, Saber L, Taskin D, Jing C, Bastidas-Ponce A, Vanheusden M, Shahryari A, Sterr M, Burtscher I, Bakhti M, Lickert H. NEUROD2 function is dispensable for human pancreatic β cell specification. Front Endocrinol (Lausanne) 2023; 14:1286590. [PMID: 37955006 PMCID: PMC10634430 DOI: 10.3389/fendo.2023.1286590] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 10/09/2023] [Indexed: 11/14/2023] Open
Abstract
Introduction The molecular programs regulating human pancreatic endocrine cell induction and fate allocation are not well deciphered. Here, we investigated the spatiotemporal expression pattern and the function of the neurogenic differentiation factor 2 (NEUROD2) during human endocrinogenesis. Methods Using Crispr-Cas9 gene editing, we generated a reporter knock-in transcription factor (TF) knock-out human inducible pluripotent stem cell (iPSC) line in which the open reading frame of both NEUROD2 alleles are replaced by a nuclear histone 2B-Venus reporter (NEUROD2nVenus/nVenus). Results We identified a transient expression of NEUROD2 mRNA and its nuclear Venus reporter activity at the stage of human endocrine progenitor formation in an iPSC differentiation model. This expression profile is similar to what was previously reported in mice, uncovering an evolutionarily conserved gene expression pattern of NEUROD2 during endocrinogenesis. In vitro differentiation of the generated homozygous NEUROD2nVenus/nVenus iPSC line towards human endocrine lineages uncovered no significant impact upon the loss of NEUROD2 on endocrine cell induction. Moreover, analysis of endocrine cell specification revealed no striking changes in the generation of insulin-producing b cells and glucagon-secreting a cells upon lack of NEUROD2. Discussion Overall, our results suggest that NEUROD2 is expendable for human b cell formation in vitro.
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Affiliation(s)
- Perla Cota
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- School of Medicine, Technical University of Munich (TUM), Munich, Germany
| | - Lama Saber
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- School of Medicine, Technical University of Munich (TUM), Munich, Germany
| | - Damla Taskin
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
| | - Changying Jing
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Munich Medical Research School (MMRS), Ludwig Maximilian University (LMU), Munich, Germany
| | - Aimée Bastidas-Ponce
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Matthew Vanheusden
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
| | - Alireza Shahryari
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
| | - Michael Sterr
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Ingo Burtscher
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Mostafa Bakhti
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Heiko Lickert
- Institute of Diabetes and Regeneration Research, Helmholtz Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- School of Medicine, Technical University of Munich (TUM), Munich, Germany
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Gräf R, Grafe M, Meyer I, Mitic K, Pitzen V. The Dictyostelium Centrosome. Cells 2021; 10:cells10102657. [PMID: 34685637 PMCID: PMC8534566 DOI: 10.3390/cells10102657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 10/01/2021] [Accepted: 10/02/2021] [Indexed: 12/13/2022] Open
Abstract
The centrosome of Dictyostelium amoebae contains no centrioles and consists of a cylindrical layered core structure surrounded by a corona harboring microtubule-nucleating γ-tubulin complexes. It is the major centrosomal model beyond animals and yeasts. Proteomics, protein interaction studies by BioID and superresolution microscopy methods led to considerable progress in our understanding of the composition, structure and function of this centrosome type. We discuss all currently known components of the Dictyostelium centrosome in comparison to other centrosomes of animals and yeasts.
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Brito C, Barral DC, Pojo M. Subversion of Ras Small GTPases in Cutaneous Melanoma Aggressiveness. Front Cell Dev Biol 2020; 8:575223. [PMID: 33072757 PMCID: PMC7538714 DOI: 10.3389/fcell.2020.575223] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/28/2020] [Indexed: 12/25/2022] Open
Abstract
The rising incidence and mortality rate associated with the metastatic ability of cutaneous melanoma represent a major public health concern. Cutaneous melanoma is one of the most invasive human cancers, but the molecular mechanisms are poorly understood. Moreover, currently available therapies are not efficient in avoiding melanoma lethality. In this context, new biomarkers of prognosis, metastasis, and response to therapy are necessary to better predict the disease outcome. Additionally, the knowledge about the molecular alterations and dysregulated pathways involved in melanoma metastasis may provide new therapeutic targets. Members of the Ras superfamily of small GTPases regulate various essential cellular activities, from signaling to membrane traffic and cytoskeleton dynamics. Therefore, it is not surprising that they are differentially expressed, and their functions subverted in several types of cancer, including melanoma. Indeed, Ras small GTPases were found to regulate melanoma progression and invasion. Hence, a better understanding of the mechanisms regulated by Ras small GTPases that are involved in melanoma tumorigenesis and progression may provide new therapeutic strategies to block these processes. Here, we review the current knowledge on the role of Ras small GTPases in melanoma aggressiveness and the molecular mechanisms involved. Furthermore, we summarize the known involvement of these proteins in melanoma metastasis and how these players influence the response to therapy.
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Affiliation(s)
- Cheila Brito
- Unidade de Investigação em Patobiologia Molecular (UIPM) do Instituto Português de Oncologia de Lisboa Francisco Gentil E.P.E., Lisbon, Portugal
| | - Duarte C Barral
- CEDOC, Faculdade de Ciências Médicas, NOVA Medical School, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Marta Pojo
- Unidade de Investigação em Patobiologia Molecular (UIPM) do Instituto Português de Oncologia de Lisboa Francisco Gentil E.P.E., Lisbon, Portugal
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Chinen T, Yamamoto S, Takeda Y, Watanabe K, Kuroki K, Hashimoto K, Takao D, Kitagawa D. NuMA assemblies organize microtubule asters to establish spindle bipolarity in acentrosomal human cells. EMBO J 2020; 39:e102378. [PMID: 31782546 PMCID: PMC6960446 DOI: 10.15252/embj.2019102378] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 11/11/2019] [Accepted: 11/12/2019] [Indexed: 12/11/2022] Open
Abstract
In most animal cells, mitotic spindle formation is mediated by coordination of centrosomal and acentrosomal pathways. At the onset of mitosis, centrosomes promote spindle bipolarization. However, the mechanism through which the acentrosomal pathways facilitate the establishment of spindle bipolarity in early mitosis is not completely understood. In this study, we show the critical roles of nuclear mitotic apparatus protein (NuMA) in the generation of spindle bipolarity in acentrosomal human cells. In acentrosomal human cells, we found that small microtubule asters containing NuMA formed at the time of nuclear envelope breakdown. In addition, these asters were assembled by dynein and the clustering activity of NuMA. Subsequently, NuMA organized the radial array of microtubules, which incorporates Eg5, and thus facilitated spindle bipolarization. Importantly, in cells with centrosomes, we also found that NuMA promoted the initial step of spindle bipolarization in early mitosis. Overall, these data suggest that canonical centrosomal and NuMA-mediated acentrosomal pathways redundantly promote spindle bipolarity in human cells.
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Affiliation(s)
- Takumi Chinen
- Division of Centrosome BiologyDepartment of Molecular GeneticsNational Institute of GeneticsMishimaShizuokaJapan
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
| | - Shohei Yamamoto
- Division of Centrosome BiologyDepartment of Molecular GeneticsNational Institute of GeneticsMishimaShizuokaJapan
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
- Graduate Program in BioscienceGraduate School of ScienceUniversity of TokyoHongoTokyoJapan
| | - Yutaka Takeda
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
| | - Koki Watanabe
- Division of Centrosome BiologyDepartment of Molecular GeneticsNational Institute of GeneticsMishimaShizuokaJapan
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
- Department of GeneticsSchool of Life ScienceThe Graduate University for Advanced Studies (SOKENDAI)HayamaKanagawaJapan
| | - Kanako Kuroki
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
| | - Kaho Hashimoto
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
| | - Daisuke Takao
- Division of Centrosome BiologyDepartment of Molecular GeneticsNational Institute of GeneticsMishimaShizuokaJapan
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
| | - Daiju Kitagawa
- Division of Centrosome BiologyDepartment of Molecular GeneticsNational Institute of GeneticsMishimaShizuokaJapan
- Department of Physiological ChemistryGraduate School of Pharmaceutical ScienceThe University of TokyoBunkyoTokyoJapan
- Department of GeneticsSchool of Life ScienceThe Graduate University for Advanced Studies (SOKENDAI)HayamaKanagawaJapan
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Elsharkawi I, Parambath D, Saber-Ayad M, Khan AA, El-Serafi AT. Exploring the effect of epigenetic modifiers on developing insulin-secreting cells. Hum Cell 2019; 33:1-9. [PMID: 31755075 DOI: 10.1007/s13577-019-00292-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 10/11/2019] [Indexed: 12/24/2022]
Abstract
Diabetes is a worldwide health problem with increasing incidence. The current management modalities did not succeed to decrease comorbidities. This study aimed at enhancing the regenerative solution for diabetes by improving the differentiation of mesenchymal stromal cells (MSC) into glucose-sensitive, insulin-secreting cells through an epigenetic modification approach. A 3-day treatment protocol with the epigenetic modifiers, either decitabine (5-aza-2'-deoxycytidine; Aza); a DNA methylation inhibitor or Vorinostat (suberoylanilide hydroxamic acid; SAHA); a histone deacetylase inhibitor was added to two different human stem cell lines. The cells followed a multi-step differentiation protocol that provided the critical triggers in a temporal approach. Aza-pretreated group showed higher intracellular expression of insulin and the transcription factor 'PDX-1'. The cells responded to the high glucose challenge by secreting insulin in the media, as shown by ELISA. Gene expression showed induction of the genes for insulin, the glucose transporter 2, glucokinase, as well as the transcription factors MafA and NKX6.1. Although SAHA showed upregulation of insulin secretion, in comparison to control, the cells could not respond to the high glucose challenge. Interestingly, Aza-treated cells showed a significant decrease in the global DNA methylation level at the end of the culture. In conclusion, this additional step with Aza could enhance the response of MSC to the classical differentiation protocol for insulin-secreting cells and may help in establishing a regenerative solution for patients with diabetes.
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Affiliation(s)
| | | | - Maha Saber-Ayad
- College of Medicine, University of Sharjah, Sharjah, UAE.,Sharjah Institute for Medical Research, University of Sharjah, Sharjah, UAE.,College of Medicine, Cairo University, Cairo, Egypt
| | - Amir Ali Khan
- Department of Applied Biology, College of Science, University of Sharjah, Sharjah, UAE
| | - Ahmed T El-Serafi
- College of Medicine, University of Sharjah, Sharjah, UAE. .,Faculty of Medicine, Suez Canal University, Ismailia, Egypt. .,Department of Hand Surgery and Plastic Surgery and Burns, 401A, Building 462, Floor 11, Linköping University Hospital, P. O. Box: 581 85, Linköping, Sweden.
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Mel1c Mediated Monochromatic Light-Stimulated IGF-I Synthesis through the Intracellular G αq/PKC/ERK Signaling Pathway. Int J Mol Sci 2019; 20:ijms20071682. [PMID: 30987295 PMCID: PMC6480035 DOI: 10.3390/ijms20071682] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 03/09/2019] [Accepted: 03/29/2019] [Indexed: 02/06/2023] Open
Abstract
Previous studies have demonstrated that monochromatic light affects plasma melatonin (MEL) levels, which in turn regulates hepatic insulin-like growth factor I (IGF-I) secretion via the Mel1c receptor. However, the intracellular signaling pathway initiated by Mel1c remains unclear. In this study, newly hatched broilers, including intact, sham operation, and pinealectomy groups, were exposed to either white (WL), red (RL), green (GL), or blue (BL) light for 14 days. Experiments in vivo showed that GL significantly promoted plasma MEL formation, which was accompanied by an increase in the MEL receptor, Mel1c, as well as phosphorylated extracellular regulated protein kinases (p-ERK1/2), and IGF-I expression in the liver, compared to the other light-treated groups. In contrast, this GL stimulation was attenuated by pinealectomy. Exogenous MEL elevated the hepatocellular IGF-I level, which is consistent with increases in cyclic adenosine monophosphate (cAMP), Gαq, phosphorylated protein kinase C (p-PKC), and p-ERK1/2 expression. However, the Mel1c selective antagonist prazosin suppressed the MEL-induced expression of IGF-I, Gαq, p-PKC, and p-ERK1/2, while the cAMP concentration was barely affected. In addition, pretreatment with Ym254890 (a Gαq inhibitor), Go9863 (a PKC inhibitor), and PD98059 (an ERK1/2 inhibitor) markedly attenuated MEL-stimulated IGF-I expression and p-ERK1/2 activity. These results indicate that Mel1c mediates monochromatic GL-stimulated IGF-I synthesis through intracellular Gαq/PKC/ERK signaling.
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Hong F, Zhou Y, Ji J, Zhuang J, Sheng L, Wang L. Nano-TiO 2 Inhibits Development of the Central Nervous System and Its Mechanism in Offspring Mice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:11767-11774. [PMID: 30269504 DOI: 10.1021/acs.jafc.8b02952] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Nano titanium dioxide (Nano-TiO2) has been applied in food packaging systems and food additives, but it may cause potential neurotoxicity for human and animals. In our study, the effects of nano-TiO2 exposure during pregnancy/lactation on the development of the central nervous system in offspring mice were examined and its molecular mechanism involving Rho family was investigated. Our findings showed that pregnancy/lactation exposure to nano-TiO2 resulted in thinning of cerebral and cerebellar cortex, decrease in number of neurons per unit area of cerebrum, edema and nuclear condensation, dysplasia of neurites in hippocampal pyramidal cells, thinning in pyramidal cell layer in hippocampus, and decrease in learning and memory of offspring mice. Furthermore, expressions of Rac1 and Cdc42 involved in axon and dendritic development were decreased, whereas RhoA expression and ratio of RhoA/Rac1 were increased in offspring brain. It implies that exposure to nano-TiO2 during pregnancy/lactation could result in brain retardation and cognitive impairment in offspring mice, which was closely related to alterations in the expression of Rho protein family. Therefore, application of nano-TiO2 in daily life should be performed with caution.
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Affiliation(s)
| | | | | | | | - Lei Sheng
- Medical College , Soochow University , Suzhou 215123 , China
| | - Ling Wang
- Library of Soochow University , Suzhou 215123 , China
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8
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Akashi K, Yoshimura K, Kajikawa M, Hanada K, Kosaka R, Kato A, Katoh A, Nanasato Y, Tsujimoto H, Yokota A. Potential involvement of drought-induced Ran GTPase CLRan1 in root growth enhancement in a xerophyte wild watermelon. Biosci Biotechnol Biochem 2016; 80:1907-16. [DOI: 10.1080/09168451.2016.1191328] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Abstract
Enhanced root growth is known as the survival strategy of plants under drought. Previous proteome analysis in drought-resistant wild watermelon has shown that Ran GTPase, an essential regulator of cell division and proliferation, was induced in the roots under drought. In this study, two cDNAs were isolated from wild watermelon, CLRan1 and CLRan2, which showed a high degree of structural similarity with those of other plant Ran GTPases. Quantitative RT-PCR and promoter-GUS assays suggested that CLRan1 was expressed mainly in the root apex and lateral root primordia, whereas CLRan2 was more broadly expressed in other part of the roots. Immunoblotting analysis confirmed that the abundance of CLRan proteins was elevated in the root apex region under drought stress. Transgenic Arabidopsis overexpressing CLRan1 showed enhanced primary root growth, and the growth was maintained under osmotic stress, indicating that CLRan1 functions as a positive factor for maintaining root growth under stress conditions.
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Affiliation(s)
- Kinya Akashi
- Faculty of Agriculture, School of Agricultural, Biological and Environmental Sciences, Tottori University, Tottori, Japan
| | - Kazuya Yoshimura
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
| | - Masataka Kajikawa
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
| | - Kouhei Hanada
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
| | - Rina Kosaka
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
| | - Atsushi Kato
- Faculty of Agriculture, School of Agricultural, Biological and Environmental Sciences, Tottori University, Tottori, Japan
| | - Akira Katoh
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
| | - Yoshihiko Nanasato
- Faculty of Agriculture, School of Agricultural, Biological and Environmental Sciences, Tottori University, Tottori, Japan
| | | | - Akiho Yokota
- Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Japan
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Chen J, Hao H, Guo G, Li S, Xiao X. Effect of Rho-kinase pathway on neurite outgrowth of rat hippocampal neurons under atomic force microscopy. Neural Regen Res 2015; 7:496-500. [PMID: 25745434 PMCID: PMC4348994 DOI: 10.3969/j.issn.1673-5374.2012.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 02/06/2012] [Indexed: 12/17/2022] Open
Abstract
Hippocampal neurons of neonatal rats were cultured in serum-free culture medium for 5 days in vitro, and treated with the Rho-kinase inducer lysophosphatidic acid. Atomic force microscopy revealed that the numbers of level-1, -2 and -3 neurites protruding from rat hippocampal neurons was significantly reduced. After treatment with the Rho kinase inhibitor Y27632, a significant increase in the numbers of these neurites was observed. Our experimental findings indicate that the Rho-kinase pathway is closely associated with the neurites of hippocampal neurons.
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Affiliation(s)
- Jing Chen
- Institute of Gastroenterology, Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou 510655, Guangdong Province, China
| | - Hu Hao
- Laboratory of Inborn Errors of Metabolism, Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou 510655, Guangdong Province, China
| | - Guoqing Guo
- Department of Anatomy, Medical College of Jinan University, Guangzhou 510632, Guangdong Province, China
| | - Sitao Li
- Laboratory of Inborn Errors of Metabolism, Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou 510655, Guangdong Province, China
| | - Xin Xiao
- Laboratory of Inborn Errors of Metabolism, Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou 510655, Guangdong Province, China
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Chen K, Zhang W, Chen J, Li S, Guo G. Rho-associated protein kinase modulates neurite extension by regulating microtubule remodeling and vinculin distribution. Neural Regen Res 2014; 8:3027-35. [PMID: 25206623 PMCID: PMC4146208 DOI: 10.3969/j.issn.1673-5374.2013.32.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 09/25/2013] [Indexed: 01/11/2023] Open
Abstract
Rho-associated protein kinase is an essential regulator of cytoskeletal dynamics during the process of neurite extension. However, whether Rho kinase regulates microtubule remodeling or the distribution of adhesive proteins to mediate neurite outgrowth remains unclear. By specifically modulating Rho kinase activity with pharmacological agents, we studied the morpho-dynamics of neurite outgrowth. We found that lysophosphatidic acid, an activator of Rho kinase, inhibited neurite outgrowth, which could be reversed by Y-27632, an inhibitor of Rho kinase. Meanwhile, reorganization of microtubules was noticed during these processes, as indicated by their significant changes in the soma and growth cone. In addition, exposure to lysophosphatidic acid led to a decreased membrane distribution of vinculin, a focal adhesion protein in neurons, whereas Y-27632 recruited vinculin to the membrane. Taken together, our data suggest that Rho kinase regulates rat hippocampal neurite growth and microtubule formation via a mechanism associated with the redistribution of vinculin.
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Affiliation(s)
- Ke'en Chen
- Department of Neurosurgery, First Affiliated Hospital of Jinan University, Guangzhou 510630, Guangdong Province, China
| | - Wenbin Zhang
- Department of Emergency, First Affiliated Hospital of Jinan University, Guangzhou 510630, Guangdong Province, China
| | - Jing Chen
- Department of Anatomy, Medical College of Jinan University, Guangzhou 510630, Guangdong Province, China
| | - Sumei Li
- Department of Anatomy, Medical College of Jinan University, Guangzhou 510630, Guangdong Province, China
| | - Guoqing Guo
- Department of Anatomy, Medical College of Jinan University, Guangzhou 510630, Guangdong Province, China
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Identification of a PTC-containing DlRan transcript and its differential expression during somatic embryogenesis in Dimocarpus longan. Gene 2013; 529:37-44. [DOI: 10.1016/j.gene.2013.07.091] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 05/19/2013] [Accepted: 07/25/2013] [Indexed: 11/17/2022]
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12
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Schappi JM, Krbanjevic A, Rasenick MM. Tubulin, actin and heterotrimeric G proteins: coordination of signaling and structure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:674-81. [PMID: 24071592 DOI: 10.1016/j.bbamem.2013.08.026] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 08/19/2013] [Accepted: 08/26/2013] [Indexed: 01/17/2023]
Abstract
G proteins mediate signals from membrane G protein coupled receptors to the cell interior, evoking significant regulation of cell physiology. The cytoskeleton contributes to cell morphology, motility, division, and transport functions. This review will discuss the interplay between heterotrimeric G protein signaling and elements of the cytoskeleton. Also described and discussed will be the interplay between tubulin and G proteins that results in atypical modulation of signaling pathways and cytoskeletal dynamics. This will be extended to describe how tubulin and G proteins act in concert to influence various aspects of cellular behavior. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters.This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
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Affiliation(s)
- Jeffrey M Schappi
- Department of Physiology and Biophysics, University Of Illinois, Chicago, IL 60612, USA
| | - Aleksandar Krbanjevic
- Department of Physiology and Biophysics, University Of Illinois, Chicago, IL 60612, USA; Jesse Brown VAMC, Chicago, IL 60612, USA
| | - Mark M Rasenick
- Department of Physiology and Biophysics, University Of Illinois, Chicago, IL 60612, USA; Department of Psychiatry, University Of Illinois, Chicago, IL 60612, USA.
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Yi K, Rubinstein B, Li R. Symmetry breaking and polarity establishment during mouse oocyte maturation. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130002. [PMID: 24062576 DOI: 10.1098/rstb.2013.0002] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mammalian oocyte meiosis encompasses two rounds of asymmetric divisions to generate a totipotent haploid egg and, as by-products, two small polar bodies. Two intracellular events, asymmetric spindle positioning and cortical polarization, are critical to such asymmetric divisions. Actin but not microtubule cytoskeleton has been known to be directly involved in both events. Recent work has revealed a positive feedback loop between chromosome-mediated cortical activation and the Arp2/3-orchestrated cytoplasmic streaming that moves chromosomes. This feedback loop not only maintains meiotic II spindle position during metaphase II arrest, but also brings about symmetry breaking during meiosis I. Prior to an Arp2/3-dependent phase of fast movement, meiotic I spindle experiences a slow and non-directional first phase of migration driven by a pushing force from Fmn2-mediated actin polymerization. In addition to illustrating these molecular mechanisms, mathematical simulations are presented to elucidate mechanical properties of actin-dependent force generation in this system.
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Affiliation(s)
- Kexi Yi
- Stowers Institute for Medical Research, , 1000 East 50th Street, Kansas City, MO 64110, USA
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14
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The road to maturation: somatic cell interaction and self-organization of the mammalian oocyte. Nat Rev Mol Cell Biol 2013; 14:141-52. [PMID: 23429793 DOI: 10.1038/nrm3531] [Citation(s) in RCA: 343] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mammalian oocytes go through a long and complex developmental process while acquiring the competencies that are required for fertilization and embryogenesis. Recent advances in molecular genetics and quantitative live imaging reveal new insights into the molecular basis of the communication between the oocyte and ovarian somatic cells as well as the dynamic cytoskeleton-based events that drive each step along the pathway to maturity. Whereas self-organization of microtubules and motor proteins direct meiotic spindle assembly for achieving genome reduction, actin filaments are instrumental for spindle positioning and the establishment of oocyte polarity needed for extrusion of polar bodies. Meiotic chromatin provides key instructive signals while being 'chauffeured' by both cytoskeletal systems.
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15
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Actin cytoskeleton in cell polarity and asymmetric division during mouse oocyte maturation. Cytoskeleton (Hoboken) 2012; 69:727-37. [DOI: 10.1002/cm.21048] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/18/2012] [Accepted: 06/21/2012] [Indexed: 12/22/2022]
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Kuhnert O, Baumann O, Meyer I, Gräf R. Functional characterization of CP148, a novel key component for centrosome integrity in Dictyostelium. Cell Mol Life Sci 2012; 69:1875-88. [PMID: 22223109 PMCID: PMC11114716 DOI: 10.1007/s00018-011-0904-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 11/16/2011] [Accepted: 12/01/2011] [Indexed: 11/28/2022]
Abstract
The Dictyostelium centrosome consists of a layered core structure surrounded by a microtubule-nucleating corona. A tight linkage through the nuclear envelope connects the cytosolic centrosome with the clustered centromeres within the nuclear matrix. At G2/M the corona dissociates, and the core structure duplicates, yielding two spindle poles. CP148 is a novel coiled coil protein of the centrosomal corona. GFP-CP148 exhibited cell cycle-dependent presence and absence at the centrosome, which correlates with dissociation of the corona in prophase and its reformation in late telophase. During telophase, GFP-CP148 formed cytosolic foci, which coalesced and joined the centrosome. This explains the hypertrophic appearance of the corona upon strong overexpression of GFP-CP148. Depletion of CP148 by RNAi caused virtual loss of the corona and disorganization of interphase microtubules. Surprisingly, formation of the mitotic spindle and astral microtubules was unaffected. Thus, microtubule nucleation complexes associate with centrosomal core components through different means during interphase and mitosis. Furthermore, CP148 RNAi caused dispersal of centromeres and altered Sun1 distribution at the nuclear envelope, suggesting a role of CP148 in the linkage between centrosomes and centromeres. Taken together, CP148 is an essential factor for the formation of the centrosomal corona, which in turn is required for centrosome/centromere linkage.
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Affiliation(s)
- Oliver Kuhnert
- Department of Cell Biology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24–25, Haus 26, 14476 Potsdam-Golm, Germany
| | - Otto Baumann
- Department of Animal Physiology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24–25, Haus 26, 14476 Potsdam-Golm, Germany
| | - Irene Meyer
- Department of Cell Biology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24–25, Haus 26, 14476 Potsdam-Golm, Germany
| | - Ralph Gräf
- Department of Cell Biology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Strasse 24–25, Haus 26, 14476 Potsdam-Golm, Germany
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17
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Hwang M, Peddibhotla S, McHenry P, Chang P, Yochum Z, Park KU, Sears JC, Vargo-Gogola T. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells. Cancers (Basel) 2012; 4:475-89. [PMID: 22582143 PMCID: PMC3348653 DOI: 10.3390/cancers4020475] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP) deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis.
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Affiliation(s)
- Melissa Hwang
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
| | - Sirisha Peddibhotla
- Department of Molecular and Human Genetics, Baylor College of Medicine, John P. McGovern Campus, NABS-0250, Houston, TX 77030, USA; E-Mail:
| | - Peter McHenry
- Department of Biology, Southwestern Adventist University, 100 W. Hillcrest, Keene, TX 76059, USA; E-Mail:
| | - Peggy Chang
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
| | - Zachary Yochum
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
| | - Ko Un Park
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
| | - James Cooper Sears
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
| | - Tracy Vargo-Gogola
- Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617, USA; E-Mails: (M.H.); (P.C.); (Z.Y); (K.U.P.); (J.C.S)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-574-631-1587; Fax: +1-574-631-7821
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18
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Dubas E, Custers J, Kieft H, Wędzony M, van Lammeren AAM. Microtubule configurations and nuclear DNA synthesis during initiation of suspensor-bearing embryos from Brassica napus cv. Topas microspores. PLANT CELL REPORTS 2011; 30:2105-16. [PMID: 21779827 PMCID: PMC3192950 DOI: 10.1007/s00299-011-1117-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 06/16/2011] [Accepted: 06/23/2011] [Indexed: 05/21/2023]
Abstract
In the new Brassica napus microspore culture system, wherein embryos with suspensors are formed, ab initio mimics zygotic embryogenesis. The system provides a powerful in vitro tool for studying the diverse developmental processes that take place during early stages of plant embryogenesis. Here, we studied in this new culture system both the temporal and spatial distribution of nuclear DNA synthesis places and the organization of the microtubular (MT) cytoskeleton, which were visualized with a refined whole mount immunolocalization technology and 3D confocal laser scanning microscopy. A 'mild' heat stress induced microspores to elongate, to rearrange their MT cytoskeleton and to re-enter the cell cycle and perform a predictable sequence of divisions. These events led to the formation of a filamentous suspensor-like structure, of which the distal tip cell gave rise to the embryo proper. Cells of the developing pro-embryo characterized endoplasmic (EMTs) and cortical microtubules (CMTs) in various configurations in the successive stages of the cell cycle. However, the most prominent changes in MT configurations and nuclear DNA replication concerned the first sporophytic division occurring within microspores and the apical cell of the pro-embryo. Microspore embryogenesis was preceded by pre-prophase band formation and DNA synthesis. The apical cell of the pro-embryo exhibited a random organization of CMTs and, in relation to this, isotropic expansion occurred, mimicking the development of the apical cell of the zygotic situation. Moreover, the apical cell entered the S phase shortly before it divided transversally at the stage that the suspensor was 3-8 celled.
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Affiliation(s)
- Ewa Dubas
- Laboratory for Plant Cell Biology, Wageningen University, Droevendaalsesteeg 1, Radix building 107, W1 6708 PB, Wageningen, The Netherlands.
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19
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Wang ZB, Ou XH, Tong JS, Li S, Wei L, Ouyang YC, Hou Y, Schatten H, Sun QY. The SUMO pathway functions in mouse oocyte maturation. Cell Cycle 2011; 9:2640-6. [PMID: 20543581 DOI: 10.4161/cc.9.13.12120] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Sumoylation is an important post-translational modification in which SUMO (small ubiquitin-related modifier) proteins are bonded covalently to their substrates. Studies on the roles of sumoylation in cell cycle regulation have been emerging in both mitosis from yeast to mammals and meiosis in budding yeast, but the functions of sumoylation in mammalian meiosis, especially in oocyte meiotic maturation are not well known. Here, we examined the localization and expression of SUMO-1 and SUMO-2/3, the two basic proteins in the sumoylation pathway and investigated their roles through over-expression of Senp2 during mouse oocyte maturation. Immunofluorescent staining revealed differential patterns of SUMO-1 and SUMO-2/3 localization: SUMO-1 was localized to the spindle poles in prometaphase I, MI and MII stages, around the separating homologues in anaphase I and telophase I stages of first meiosis, while SUMO-2/3 was mainly concentrated near centromeres during mouse oocyte maturation. Immunoblot analysis uncovered the different expression profiles of SUMO-1 and SUMO-2/3 modified proteins during mouse oocyte maturation. Over-expression of Senp2, a SUMO-specific isopeptidase, caused changes of SUMO-modified proteins and led to defects in MII spindle organization in mature eggs. These results suggest that the SUMO pathway may play an indispensable role during mouse oocyte meiotic maturation.
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Affiliation(s)
- Zhen-Bo Wang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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20
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Abstract
Small GTPases are key molecular switches that bind and hydrolyze GTP in diverse membrane- and cytoskeleton-related cellular processes. Recently, mounting evidences have highlighted the role of various small GTPases, including the members in Arf/Arl, Rab, and Ran subfamilies, in cilia formation and function. Once overlooked as an evolutionary vestige, the primary cilium has attracted more and more attention in last decade because of its role in sensing various extracellular signals and the association between cilia dysfunction and a wide spectrum of human diseases, now called ciliopathies. Here we review recent advances about the function of small GTPases in the context of cilia, and the correlation between the functional impairment of small GTPases and ciliopathies. Understanding of these cellular processes is of fundamental importance for broadening our view of cilia development and function in normal and pathological states and for providing valuable insights into the role of various small GTPases in disease processes, and their potential as therapeutic targets.
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Affiliation(s)
- Yujie Li
- Department of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
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21
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Chen THH, Murata N. Glycinebetaine protects plants against abiotic stress: mechanisms and biotechnological applications. PLANT, CELL & ENVIRONMENT 2011; 34:52-64. [PMID: 20825577 DOI: 10.1111/j.1365-3040.2010.02225.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Various compatible solutes enable plants to tolerate abiotic stress, and glycinebetaine (GB) is one of the most-studied among such solutes. Early research on GB focused on the maintenance of cellular osmotic potential in plant cells. Subsequent genetically engineered synthesis of GB-biosynthetic enzymes and studies of transgenic plants demonstrated that accumulation of GB increases tolerance of plants to various abiotic stresses at all stages of their life cycle. Such GB-accumulating plants exhibit various advantageous traits, such as enlarged fruits and flowers and/or increased seed number under non-stress conditions. However, levels of GB in transgenic GB-accumulating plants are relatively low being, generally, in the millimolar range. Nonetheless, these low levels of GB confer considerable tolerance to various stresses, without necessarily contributing significantly to cellular osmotic potential. Moreover, low levels of GB, applied exogenously or generated by transgenes for GB biosynthesis, can induce the expression of certain stress-responsive genes, including those for enzymes that scavenge reactive oxygen species. Thus, transgenic approaches that increase tolerance to abiotic stress have enhanced our understanding of mechanisms that protect plants against such stress.
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Affiliation(s)
- Tony H H Chen
- Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA National Institute for Basic Biology, Okazaki 444-8585, Japan
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22
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Kuroda H, Saito K, Kuroda M, Suzuki Y. Differential expression of glu-tubulin in relation to mammary gland disease. Virchows Arch 2010; 457:477-82. [PMID: 20697907 DOI: 10.1007/s00428-010-0955-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 06/17/2010] [Accepted: 07/25/2010] [Indexed: 12/13/2022]
Abstract
Tubulin is one of the molecular components that regulate cytosketal structure relating to cell differentiation, invasion, and metastasis in cancer. Recently, glu-tubulin, in which the C-terminal tyrosine of α-tubulin is removed by tubulin carboxypeptidase, overexpression has been reported in malignant tumors of the mammary gland immunohistochemically. We identified 147 cases accessioned in the Department of Pathology, International University of Health and Welfare Hospital from 2003 to 2009. Of the 78 malignant tumor cases, staining for glu-tubulin was observed in 56 (71.8%), and only 22 cases showed no significant staining. However, in benign disease, glu-tubulin staining was detected in the cytoplasm of fibroblasts and endothelial cells, but was completely absent from epithelial cells in 64 of 69 cases. When the expression of glu-tubulin was compared between malignant tumor, benign tumor, and other benign disease, a significant differentiation was found among expressions of this protein. These results indicate that glu-tubulin represents a strong selective expression for cancer cells and may be useful to identify and quantify human breast cancer.
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Affiliation(s)
- Hajime Kuroda
- Department of Pathology, International University of Health and Welfare Hospital, Nasushiobara, Tochigi 329-2763, Japan.
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23
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Chang Y, Paramasivam M, Girgenti MJ, Walikonis RS, Bianchi E, LoTurco JJ. RanBPM regulates the progression of neuronal precursors through M-phase at the surface of the neocortical ventricular zone. Dev Neurobiol 2010; 70:1-15. [PMID: 19790105 DOI: 10.1002/dneu.20750] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Many of the mitoses that produce pyramidal neurons in neocortex occur at the dorsolateral surface of the lateral ventricles in the embryo. RanBPM was found in a yeast two-hybrid screen to potentially interact with citron kinase (CITK), a protein shown previously to localize to the surface of the lateral ventricles and to be essential to neurogenic mitoses. Similar to its localization in epithelia, RanBPM protein is concentrated at the adherens junctions in developing neocortex. The biochemical interaction between CITK and RanBPM was confirmed in coimmunoprecipitation and protein overlay experiments. To test for a functional role of RanPBM in vivo, we used in utero RNAi. RanBPM RNAi decreased the polarization of CITK to the ventricular surface, increased the number of cells in mitosis, and decreased the number of cells in cytokinesis. Finally, the effect of RanBPM knockdown on mitosis was reversed in embryos mutant for CITK. Together, these results indicate that RanBPM, potentially through interaction with CITK, plays a role in the progression of neocortical precursors through M-phase at the ventricular surface.
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Affiliation(s)
- Yoonjeung Chang
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
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24
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Sato M, Toda T. Space shuttling in the cell: nucleocytoplasmic transport and microtubule organization during the cell cycle. NUCLEUS (AUSTIN, TEX.) 2010; 1:231-6. [PMID: 21327068 DOI: 10.4161/nucl.1.3.11443] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 01/31/2010] [Accepted: 02/08/2010] [Indexed: 12/12/2022]
Abstract
Microtubules form a multifunctional filamentous structure essential for the cell. In interphase, microtubules form networks in the cytoplasm and play pivotal roles in cell polarity and intracellular transport of various biomolecules. In mitosis, microtubules dramatically change their morphology to assemble the mitotic spindle, thereby pulling the chromosomes toward the spindle poles. One long-standing question is how microtubules are reorganized upon mitotic entry. Yeast cells undergo closed mitosis, in which the nuclear envelope persists, whereas higher eukaryotes undergo open mitosis, in which the nuclear envelope breaks down. Microtubule reorganization must be controlled by selective localization of microtubule-assembly factors. Recent findings in fission yeast indicate that several microtubule-associated proteins (MAPs) shuttle between the cytoplasm and the nucleus through regulation by Ran GTPase, the universal organizer of nucleocytoplasmic transport. Furthermore, the synergistic interplay of Ran and cyclin-dependent kinase (CDK) induces the critical spatiotemporal shift of modes in microtubule assembly from cytoplasmic arrays to nuclear spindles. A MAP complex Alp7/TACC-Alp14/TOG undergoes nucleocytoplasmic shuttling in interphase, whereas it is retained in the mitotic nucleus through a decrease of its nuclear export by CDK. Our understanding of how microtubules are reorganized during the cell cycle is beginning to emerge.
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Affiliation(s)
- Masamitsu Sato
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Japan.
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25
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Abstract
Cytoskeletal systems are networks of polymers found in all eukaryotic and many prokaryotic cells. Their purpose is to transmit and integrate information across cellular dimensions and help turn a disorderly mob of macromolecules into a spatially organized, living cell. Information, in this context, includes physical and chemical properties relevant to cellular physiology, including: the number and activity of macromolecules, cell shape, and mechanical force. Most animal cells are 10-50 microns in diameter, whereas the macromolecules that comprise them are 10,000-fold smaller (2-20 nm). To establish long-range order over cellular length scales, individual molecules must, therefore, self-assemble into larger polymers, with lengths (0.1-20 m) comparable to the size of a cell. These polymers must then be cross-linked into organized networks that fill the cytoplasm. Such cell-spanning polymer networks enable different parts of the cytoplasm to communicate directly with each other, either by transmitting forces or by carrying cargo from one spot to another.
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Affiliation(s)
- R Dyche Mullins
- N312F Genentech Hall, UCSF School of Medicine, 600 16th Street, San Francisco, California 94158, USA.
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26
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Leishmania donovani Ran-GTPase interacts at the nuclear rim with linker histone H1. Biochem J 2009; 424:367-74. [DOI: 10.1042/bj20090576] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ran-GTPase regulates multiple cellular processes such as nucleocytoplasmic transport, mitotic spindle assembly, nuclear envelope assembly, cell-cycle progression and the mitotic checkpoint. The leishmanial Ran protein, in contrast with its mammalian counterpart which is predominately nucleoplasmic, is localized at the nuclear rim. The aim of the present study was to characterize the LdRan (Leishmania donovani Ran) orthologue with an emphasis on the Ran–histone association. LdRan was found to be developmentally regulated, expressed 3-fold less in the amastigote stage. LdRan overexpression caused a growth defect linked to a delayed S-phase progression in promastigotes as for its mammalian counterpart. We report for the first time that Ran interacts with a linker histone, histone H1, in vitro and that the two proteins co-localize at the parasite nuclear rim. Interaction of Ran with core histones H3 and H4, creating in metazoans a chromosomal Ran-GTP gradient important for mitotic spindle assembly, is speculative in Leishmania spp., not only because this parasite undergoes a closed mitosis, but also because the main localization of LdRan is different from that of core histone H3. Interaction of Ran with the leishmanial linker histone H1 (LeishH1) suggests that this association maybe involved in modulation of pathways other than those documented for the metazoan Ran–core histone association.
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27
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Medendorp K, van Groningen JJM, Vreede L, Hetterschijt L, van den Hurk WH, de Bruijn DRH, Brugmans L, Geurts van Kessel A. The mitotic arrest deficient protein MAD2B interacts with the small GTPase RAN throughout the cell cycle. PLoS One 2009; 4:e7020. [PMID: 19753112 PMCID: PMC2737141 DOI: 10.1371/journal.pone.0007020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 08/17/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Previously, we identified the mitotic arrest deficient protein MAD2B (MAD2L2) as a bona fide interactor of the renal cell carcinoma (RCC)-associated protein PRCC. In addition, we found that fusion of PRCC with the transcription factor TFE3 in t(X;1)(p11;q21)-positive RCCs results in an impairment of this interaction and, concomitantly, an abrogation of cell cycle progression. Although MAD2B is thought to inhibit the anaphase promoting complex (APC) by binding to CDC20 and/or CDH1(FZR1), its exact role in cell cycle control still remains to be established. METHODOLOGY/PRINCIPAL FINDINGS Using a yeast two-hybrid interaction trap we identified the small GTPase RAN, a well-known cell cycle regulator, as a novel MAD2B binding protein. Endogenous interaction was established in mammalian cells via co-localization and co-immunoprecipitation of the respective proteins. The interaction domain of RAN could be assigned to a C-terminal moiety of 60 amino acids, whereas MAD2B had to be present in its full-length conformation. The MAD2B-RAN interaction was found to persist throughout the cell cycle. During mitosis, co-localization at the spindle was observed. CONCLUSIONS/SIGNIFICANCE The small GTPase RAN is a novel MAD2B binding protein. This novel protein-protein interaction may play a role in (i) the control over the spindle checkpoint during mitosis and (ii) the regulation of nucleocytoplasmic trafficking during interphase.
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Affiliation(s)
- Klaas Medendorp
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Jan J. M. van Groningen
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Lilian Vreede
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Lisette Hetterschijt
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Wilhelmina H. van den Hurk
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Diederik R. H. de Bruijn
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Linda Brugmans
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Ad Geurts van Kessel
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
- * E-mail:
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28
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Nucleocytoplasmic transport of Alp7/TACC organizes spatiotemporal microtubule formation in fission yeast. EMBO Rep 2009; 10:1161-7. [PMID: 19696784 PMCID: PMC2731110 DOI: 10.1038/embor.2009.158] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 06/12/2009] [Accepted: 06/15/2009] [Indexed: 11/17/2022] Open
Abstract
Ran GTPase activates several target molecules to induce microtubule formation around the chromosomes and centrosomes. In fission yeast, in which the nuclear envelope does not break down during mitosis, Ran targets the centrosomal transforming acidic coiled-coil (TACC) protein Alp7 for spindle formation. Alp7 accumulates in the nucleus only during mitosis, although its underlying mechanism remains elusive. Here, we investigate the behaviour of Alp7 and its binding partner, Alp14/TOG, throughout the cell cycle. Interestingly, Alp7 enters the nucleus during interphase but is subsequently exported to the cytoplasm by the Exportin-dependent nuclear export machinery. The continuous nuclear export of Alp7 during interphase is essential for maintaining the array-like cytoplasmic microtubule structure. The mitosis-specific nuclear accumulation of Alp7 seems to be under the control of cyclin-dependent kinase (CDK). These results indicate that the spatiotemporal regulation of microtubule formation is established by the Alp7/TACC–Alp14/TOG complex through the coordinated interplay of Ran and CDK.
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29
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Tartakoff AM, Tao T. Comparative and evolutionary aspects of macromolecular translocation across membranes. Int J Biochem Cell Biol 2009; 42:214-29. [PMID: 19643202 DOI: 10.1016/j.biocel.2009.07.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/21/2009] [Accepted: 07/21/2009] [Indexed: 01/10/2023]
Abstract
Membrane barriers preserve the integrity of organelles of eukaryotic cells, yet the genesis and ongoing functions of the same organelles requires that their limiting membranes allow import and export of selected macromolecules. Multiple distinct mechanisms are used for this purpose, only some of which have been traced to prokaryotes. Some can accommodate both monomeric and also large heterooligomeric cargoes. The best characterized of these is nucleocytoplasmic transport. This synthesis compares the unidirectional and bidirectional mechanisms of macromolecular transport of the endoplasmic reticulum, mitochondria, peroxisomes and the nucleus, calls attention to the powerful experimental approaches which have been used for their elucidation, discusses their regulation and evolutionary origins, and highlights relatively unexplored areas.
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Affiliation(s)
- Alan M Tartakoff
- Department of Pathology & Cell Biology Program, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
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30
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Meiotic regulation of TPX2 protein levels governs cell cycle progression in mouse oocytes. PLoS One 2008; 3:e3338. [PMID: 18833336 PMCID: PMC2556383 DOI: 10.1371/journal.pone.0003338] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 09/12/2008] [Indexed: 01/17/2023] Open
Abstract
Formation of female gametes requires acentriolar spindle assembly during meiosis. Mitotic spindles organize from centrosomes and via local activation of the RanGTPase on chromosomes. Vertebrate oocytes present a RanGTP gradient centred on chromatin at all stages of meiotic maturation. However, this gradient is dispensable for assembly of the first meiotic spindle. To understand this meiosis I peculiarity, we studied TPX2, a Ran target, in mouse oocytes. Strikingly, TPX2 activity is controlled at the protein level through its accumulation from meiosis I to II. By RNAi depletion and live imaging, we show that TPX2 is required for spindle assembly via two distinct functions. It controls microtubule assembly and spindle pole integrity via the phosphorylation of TACC3, a regulator of MTOCs activity. We show that meiotic spindle formation in vivo depends on the regulation of at least a target of Ran, TPX2, rather than on the regulation of the RanGTP gradient itself.
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31
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Unsworth A, Masuda H, Dhut S, Toda T. Fission yeast kinesin-8 Klp5 and Klp6 are interdependent for mitotic nuclear retention and required for proper microtubule dynamics. Mol Biol Cell 2008; 19:5104-15. [PMID: 18799626 DOI: 10.1091/mbc.e08-02-0224] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Fission yeast has two kinesin-8s, Klp5 and Klp6, which associate to form a heterocomplex. Here, we show that Klp5 and Klp6 are mutually dependent on each other for nuclear mitotic localization. During interphase, they are exported to the cytoplasm. In sharp contrast, during mitosis, Klp5 and Klp6 remain in the nucleus, which requires the existence of each counterpart. Canonical nuclear localization signal (NLS) is identified in the nonkinesin C-terminal regions. Intriguingly individual NLS mutants (NLSmut) exhibit loss-of-function phenotypes, suggesting that Klp5 and Klp6 enter the nucleus separately. Indeed, although neither Klp5-NLSmut nor Klp6-NLSmut enters the nucleus, wild-type Klp6 or Klp5, respectively, does so with different kinetics. In the absence of Klp5/6, microtubule catastrophe/rescue frequency and dynamicity are suppressed, whereas growth and shrinkage rates are least affected. Remarkably, chimera strains containing only the N-terminal Klp5 kinesin domains cannot disassemble interphase microtubules during mitosis, leading to the coexistence of cytoplasmic microtubules and nuclear spindles with massive chromosome missegregation. In this strain, a marked reduction of microtubule dynamism, even higher than in klp5/6 deletions, is evident. We propose that Klp5 and Klp6 play a vital role in promoting microtubule dynamics, which is essential for the spatiotemporal control of microtubule morphogenesis.
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Affiliation(s)
- Amy Unsworth
- Laboratory of Cell Regulation Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, United Kingdom
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Verlhac MH, Dumont J. Interactions between chromosomes, microfilaments and microtubules revealed by the study of small GTPases in a big cell, the vertebrate oocyte. Mol Cell Endocrinol 2008; 282:12-7. [PMID: 18191018 DOI: 10.1016/j.mce.2007.11.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Meiotic divisions during oogenesis in higher eukaryotes are extremely asymmetric giving rise to one gamete, the oocyte, and two polar bodies. In most species, this asymmetric partitioning relies on the eccentric positioning of meiotic spindles. Recent work performed in mouse and frog oocytes has suggested the involvement of small GTPases, such as Cdc42, Rac and Ran both in the control of spindle organization and positioning. The present review summarizes these findings that shed light on the molecular mechanisms by which small GTPases control asymmetric cell divisions in vertebrate oocytes.
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Affiliation(s)
- Marie-Hélène Verlhac
- Equipe Divisions Méiotiques chez la souris, CNRS/Université Pierre et Marie Curie, UMR7622, Bat. C 5e, 9 quai Saint Bernard, 75005 Paris, France.
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Neuwald AF. Galpha Gbetagamma dissociation may be due to retraction of a buried lysine and disruption of an aromatic cluster by a GTP-sensing Arg Trp pair. Protein Sci 2008; 16:2570-7. [PMID: 17962409 DOI: 10.1110/ps.073098107] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The heterotrimeric G protein alpha subunit (Galpha) functions as a molecular switch by cycling between inactive GDP-bound and active GTP-bound states. When bound to GDP, Galpha interacts with high affinity to a complex of the beta and gamma subunits (Gbetagamma), but when bound to GTP, Galpha dissociates from this complex to activate downstream signaling pathways. Galpha's state is communicated to other cellular components via conformational changes within its switch I and II regions. To identify key determinants of Galpha's function as a signaling pathway molecular switch, a Bayesian approach was used to infer the selective constraints that most distinguish Galpha and closely related Arf family GTPases from distantly related translational and metabolic GTPases. The strongest of these constraints are imposed on seven residues within or near the switch II region. Likewise, constraints imposed on Galpha but not on other, closely related molecular switches correspond to four nearby residues. These constraints are explained by a proposed mechanism for GTP-induced dissociation of Galpha from Gbetagamma where an Arg-Trp pair senses the presence of bound GTP leading to conformational retraction of a nearby lysine and to disruption of an aromatic cluster. Within a complex of Gialpha, Gibetagamma, and GDP, this lysine establishes greater surface contact with Gibeta than does any other residue in Gialpha, whereas the aromatic cluster packs against a highly conserved tryptophan in Gibeta that establishes greater surface contact with Gialpha than does any other residue in Gibeta. Other structural features associated with Galpha functional divergence further support the proposed mechanism.
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Nadif Kasri N, Van Aelst L. Rho-linked genes and neurological disorders. Pflugers Arch 2007; 455:787-97. [PMID: 18004590 DOI: 10.1007/s00424-007-0385-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Accepted: 10/29/2007] [Indexed: 12/11/2022]
Abstract
Mental retardation (MR) is a common cause of intellectual disability and affects approximately 2 to 3% of children and young adults. Many forms of MR are associated with abnormalities in dendritic structure and/or dendritic spine morphology. Given that dendritic spine morphology has been tightly linked to synaptic activity, altered spine morphology has been suggested to underlie or contribute to the cognitive disabilities associated with MR. The structure and dynamics of dendritic spines is determined by its underlying actin cytoskeleton. Signaling molecules and cascades important for cytoskeletal regulation have therefore attracted a great deal of attention. As key regulators of both the actin and microtubule cytoskeletons, it is not surprising that the Rho GTPases have emerged as important regulators of dendrite and spine structural plasticity. Significantly, mutations in regulators and effectors of Rho GTPases have been associated with diseases affecting the nervous system, including MR and amyotrophic lateral sclerosis (ALS). Here, we will discuss Rho GTPase-related genes and their signaling pathways involved in MR and ALS.
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Affiliation(s)
- Nael Nadif Kasri
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Demerec Building, Cold Spring Harbor, NY 11724, USA.
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Kotwaliwale CV, Frei SB, Stern BM, Biggins S. A pathway containing the Ipl1/aurora protein kinase and the spindle midzone protein Ase1 regulates yeast spindle assembly. Dev Cell 2007; 13:433-45. [PMID: 17765685 PMCID: PMC2679386 DOI: 10.1016/j.devcel.2007.07.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 04/23/2007] [Accepted: 07/11/2007] [Indexed: 11/25/2022]
Abstract
It is critical to elucidate the pathways that mediate spindle assembly and therefore ensure accurate chromosome segregation during cell division. Our studies of a unique allele of the budding yeast Ipl1/Aurora protein kinase revealed that it is required for centrosome-mediated spindle assembly in the absence of the BimC motor protein Cin8. In addition, we found that the Ase1 spindle midzone-associated protein is required for bipolar spindle assembly. The cin8 ipl1 and cin8 ase1 double mutant cells exhibit similar defects, and Ase1 overexpression completely restores spindle assembly in cin8 ipl1 strains. Consistent with the possibility that Ipl1 regulates Ase1, an ase1 mutant lacking the Ipl1 consensus phosphorylation sites cannot assemble spindles in the absence of Cin8. In addition, Ase1 phosphorylation and localization were altered in an ipl1 mutant. We therefore propose that Ipl1/Aurora and Ase1 constitute a previously unidentified spindle assembly pathway that becomes essential in the absence of Cin8.
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Affiliation(s)
- Chitra V. Kotwaliwale
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, PO Box 19024, Seattle, Washington 98109
| | - Stéphanie Buvelot Frei
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, PO Box 19024, Seattle, Washington 98109
| | - Bodo M. Stern
- Harvard FAS Center for Systems Biology, Bauer Laboratory, 7 Divinity Avenue, Cambridge MA 02138
| | - Sue Biggins
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, PO Box 19024, Seattle, Washington 98109
- Contact: , 206-667-1351 (phone), 206-667-6526 (fax)
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Chen H, Firestein BL. RhoA regulates dendrite branching in hippocampal neurons by decreasing cypin protein levels. J Neurosci 2007; 27:8378-86. [PMID: 17670984 PMCID: PMC6673065 DOI: 10.1523/jneurosci.0872-07.2007] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The way a dendrite is patterned determines how a neuron will receive information. The Rho GTPases have been reported to play increasingly well defined roles in determining dendritic branch and spine development and morphology. Much is known about how these small GTPases regulate the actin cytoskeleton; however, very little is known about how they alter the microtubule cytoskeleton. Our laboratory previously cloned and characterized cypin, a guanine deaminase that increases dendrite number by binding to tubulin heterodimers and promoting microtubule assembly. In the present study, we show that cypin and RhoA are part of a common pathway that regulates dendrite number. Inhibition of Rho kinase activity does not affect cypin-mediated dendrite branching. Furthermore, cypin does not affect the activity of RhoA, as measured by GTP binding to RhoA. In fact, activated RhoA acts to inhibit cypin protein expression and, by doing so, decreases dendrite number. In addition, this decrease in cypin protein occurs via a translation-dependent mechanism. Together, our data suggest that cypin acts downstream of the small GTPase RhoA to regulate dendrite branching in hippocampal neurons, providing a novel mechanism for RhoA action on microtubule dynamics.
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Affiliation(s)
- Hongxin Chen
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854-8082
| | - Bonnie L. Firestein
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854-8082
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Ribbeck K, Raemaekers T, Carmeliet G, Mattaj IW. A role for NuSAP in linking microtubules to mitotic chromosomes. Curr Biol 2007; 17:230-6. [PMID: 17276916 DOI: 10.1016/j.cub.2006.11.050] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 11/12/2006] [Accepted: 11/16/2006] [Indexed: 10/23/2022]
Abstract
The spindle apparatus is a microtubule (MT)-based machinery that attaches to and segregates the chromosomes during mitosis and meiosis. Self-organization of the spindle around chromatin involves the assembly of MTs, their attachment to the chromosomes, and their organization into a bipolar array. One regulator of spindle self-organization is RanGTP. RanGTP is generated at chromatin and activates a set of soluble, Ran-regulated spindle factors such as TPX2, NuMA, and NuSAP . How the spindle factors direct and attach MTs to the chromosomes are key open questions. Nucleolar and Spindle-Associated Protein (NuSAP) was recently identified as an essential MT-stabilizing and bundling protein that is enriched at the central part of the spindle . Here, we show by biochemical reconstitution that NuSAP efficiently adsorbs to isolated chromatin and DNA and that it can directly produce and retain high concentrations of MTs in the immediate vicinity of chromatin or DNA. Moreover, our data reveal that NuSAP-chromatin interaction is subject to Ran regulation and can be suppressed by Importin alpha (Impalpha) and Imp7. We propose that the presence of MT binding agents such as NuSAP, which can be directly immobilized on chromatin, are critical for targeting MT production to vertebrate chromosomes during spindle self-organization.
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Affiliation(s)
- Katharina Ribbeck
- European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
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Dumont J, Petri S, Pellegrin F, Terret ME, Bohnsack MT, Rassinier P, Georget V, Kalab P, Gruss OJ, Verlhac MH. A centriole- and RanGTP-independent spindle assembly pathway in meiosis I of vertebrate oocytes. ACTA ACUST UNITED AC 2007; 176:295-305. [PMID: 17261848 PMCID: PMC2063956 DOI: 10.1083/jcb.200605199] [Citation(s) in RCA: 178] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spindle formation is essential for stable inheritance of genetic material. Experiments in various systems indicate that Ran GTPase is crucial for meiotic and mitotic spindle assembly. Such an important role for Ran in chromatin-induced spindle assembly was initially demonstrated in Xenopus laevis egg extracts. However, the requirement of RanGTP in living meiotic cells has not been shown. In this study, we used a fluorescence resonance energy transfer probe to measure RanGTP-regulated release of importin β. A RanGTP-regulated gradient was established during meiosis I and was centered on chromosomes throughout mouse meiotic maturation. Manipulating levels of RanGTP in mice and X. laevis oocytes did not inhibit assembly of functional meiosis I spindles. However, meiosis II spindle assembly did not tolerate changes in the level of RanGTP in both species. These findings suggest that a mechanism common to vertebrates promotes meiosis I spindle formation in the absence of chromatin-induced microtubule production and centriole-based microtubule organizing centers.
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Affiliation(s)
- Julien Dumont
- UMR7622, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, 75005 Paris, France
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Sato M, Toda T. Alp7/TACC is a crucial target in Ran-GTPase-dependent spindle formation in fission yeast. Nature 2007; 447:334-7. [PMID: 17476213 DOI: 10.1038/nature05773] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Accepted: 03/23/2007] [Indexed: 11/09/2022]
Abstract
Microtubules are essential intracellular structures involved in several cellular phenomena, including polarity establishment and chromosome segregation. Because the nuclear envelope persists during mitosis (closed mitosis) in fission yeast (Schizosaccharomyces pombe), cytoplasmic microtubules must be reorganized into the spindle in the compartmentalized nucleus on mitotic entry. An ideal mechanism might be to take advantage of an evolutionarily conserved microtubule formation system that uses the Ran-GTPase nuclear transport machinery, but no targets of Ran for spindle formation have been identified in yeast. Here we show that a microtubule-associated protein, Alp7, which forms a complex with Alp14, is a target of Ran in yeast for spindle formation. The Ran-deficient pim1 mutant (pim1-F201S) failed to show mitosis-specific nuclear accumulation of Alp7. Moreover, this mutant exhibited compromised spindle formation and early mitotic delay. Importantly, these defects were suppressed by Alp7 that was artificially targeted to the nucleus by a Ran-independent and importin-alpha-mediated system. Thus, Ran targets Alp7-Alp14 to achieve nuclear spindle formation, and might differentiate its targets depending on whether the organism undergoes closed or open mitosis.
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Affiliation(s)
- Masamitsu Sato
- Laboratory of Cell Regulation, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
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Sánchez-Soriano N, Tear G, Whitington P, Prokop A. Drosophila as a genetic and cellular model for studies on axonal growth. Neural Dev 2007; 2:9. [PMID: 17475018 PMCID: PMC1876224 DOI: 10.1186/1749-8104-2-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2007] [Accepted: 05/02/2007] [Indexed: 11/10/2022] Open
Abstract
One of the most fascinating processes during nervous system development is the establishment of stereotypic neuronal networks. An essential step in this process is the outgrowth and precise navigation (pathfinding) of axons and dendrites towards their synaptic partner cells. This phenomenon was first described more than a century ago and, over the past decades, increasing insights have been gained into the cellular and molecular mechanisms regulating neuronal growth and navigation. Progress in this area has been greatly assisted by the use of simple and genetically tractable invertebrate model systems, such as the fruit fly Drosophila melanogaster. This review is dedicated to Drosophila as a genetic and cellular model to study axonal growth and demonstrates how it can and has been used for this research. We describe the various cellular systems of Drosophila used for such studies, insights into axonal growth cones and their cytoskeletal dynamics, and summarise identified molecular signalling pathways required for growth cone navigation, with particular focus on pathfinding decisions in the ventral nerve cord of Drosophila embryos. These Drosophila-specific aspects are viewed in the general context of our current knowledge about neuronal growth.
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Affiliation(s)
- Natalia Sánchez-Soriano
- The Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
| | - Guy Tear
- MRC Centre for Developmental Neurobiology, Guy's Campus, King's College, London, UK
| | - Paul Whitington
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria, Australia
| | - Andreas Prokop
- The Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
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Kim HJ, Yano A, Wada Y, Sano H. Properties of a tobacco DNA methyltransferase, NtMET1 and its involvement in chromatin movement during cell division. ANNALS OF BOTANY 2007; 99:845-56. [PMID: 17337479 PMCID: PMC2802912 DOI: 10.1093/aob/mcm021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 12/05/2006] [Accepted: 01/09/2007] [Indexed: 05/12/2023]
Abstract
BACKGROUND AND AIMS Plants possess three types of DNA methyltransferase, among which methyltransferase type 1 (MET1) is considered to play a major role by maintaining the CpG methylation patterns. However, little information is available as to its enzymatic activity, interacting proteins and spatial and temporal behaviours during DNA replication. In the present study, one example, NtMET1 from tobacco plants, was selected and an analysis was made of its biochemical properties and cellular localization. METHODS NtMET1 was expressed in Sf9 insect cells, and a purified sample was subjected to a standard in vitro methylation assay. Intramolecular interaction was examined by the yeast two-hybrid and pull-down assays. Transgenic tobacco plants (Nicotiana tabacum) over-expressing NtMET1 were constructed via Agrobacterium-mediated transformation. Cellular localization was examined by fluorescence protein fusion, which was expressed in tobacco bright yellow 2 cells. KEY RESULTS In vitro assays showed no detectable methylation activity when both hemimethylated and unmethylated DNA samples were used as the substrate. In planta assays with over-expressing transgenic lines showed no hypermethylation but rather hypomethylation of genomc DNA. The inability of methylation was conceivably due to a tight intramolecular interaction between the N- and C-terminal regions with the catalytic domain residing on the C-terminus being completely masked. Cellular localization analyses indicated that NtMET1 localized to the nucleus in the resting stage and migrates to the cytoplasm during mitosis, particularly at metaphase. The pattern observed resembled that of Ran GTPase, and in vitro pull-down assays showed a clear interaction between NtMET1 and AtRAN3, an Arabidopsis orthologue of tobacco Ran GTPase, NtRan-A1. CONCLUSIONS The results suggest that enzymatic activity of NtMET1 is well adjusted by its own intra/intermolecular interaction and perhaps by interactions with other proteins, one of which was found to be Ran GTPase. Results also revealed that NtMET1 becomes localized to the vicinity of chromatin with the aid of Ran GTPase during cell division, and may play an important role in progress through mitosis independently of methylation activity.
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Affiliation(s)
| | | | | | - Hiroshi Sano
- Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Nara 630-0192, Japan
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Clausen T, Ribbeck K. Self-organization of anastral spindles by synergy of dynamic instability, autocatalytic microtubule production, and a spatial signaling gradient. PLoS One 2007; 2:e244. [PMID: 17330139 PMCID: PMC1797610 DOI: 10.1371/journal.pone.0000244] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Accepted: 01/24/2007] [Indexed: 02/06/2023] Open
Abstract
Assembly of the mitotic spindle is a classic example of macromolecular self-organization. During spindle assembly, microtubules (MTs) accumulate around chromatin. In centrosomal spindles, centrosomes at the spindle poles are the dominating source of MT production. However, many systems assemble anastral spindles, i.e., spindles without centrosomes at the poles. How anastral spindles produce and maintain a high concentration of MTs in the absence of centrosome-catalyzed MT production is unknown. With a combined biochemistry-computer simulation approach, we show that the concerted activity of three components can efficiently concentrate microtubules (MTs) at chromatin: (1) an external stimulus in form of a RanGTP gradient centered on chromatin, (2) a feed-back loop where MTs induce production of new MTs, and (3) continuous re-organization of MT structures by dynamic instability. The mechanism proposed here can generate and maintain a dissipative MT super-structure within a RanGTP gradient.
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Affiliation(s)
- Thomas Clausen
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - Katharina Ribbeck
- European Molecular Biology Laboratory, Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail:
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Goodman B, Zheng Y. Mitotic spindle morphogenesis: Ran on the microtubule cytoskeleton and beyond. Biochem Soc Trans 2007; 34:716-21. [PMID: 17052181 DOI: 10.1042/bst0340716] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Assembly and disassembly of the mitotic spindle are essential for both chromosome segregation and cell division. The small G-protein Ran has emerged as an important regulator of spindle assembly. In this review, we look at the role of Ran in different aspects of spindle assembly, including its effects on microtubule assembly dynamics and microtubule organization. In addition, we examine the possibility of a spindle matrix and the role Ran might play in such a structure.
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Affiliation(s)
- B Goodman
- Department of Embryology, Carnegie Institution of Washington, Johns Hopkins University, Baltimore, MD 21218, USA
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Abstract
Katanin is a conserved AAA ATPase with the ability to sever microtubules, but its biological function in animal cells has been obscure. A recent study using electron tomography has found that katanin stimulates the production of microtubules in the meiotic spindles of Caenorhabditis elegans oocytes.
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Affiliation(s)
- Katharina Ribbeck
- Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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45
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Lippert JW. Vascular disrupting agents. Bioorg Med Chem 2007; 15:605-15. [PMID: 17070061 DOI: 10.1016/j.bmc.2006.10.020] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 10/03/2006] [Accepted: 10/11/2006] [Indexed: 11/25/2022]
Abstract
A clear definition for vascular targeting agents (VTAs) and vascular disrupting agents (VDAs) has separated the two as distinct methods of cancer treatment. VDAs differ from VTAs (antiangiogenesis drugs) in their mechanism of action. VTAs attempt to keep new blood vessels from forming and do not act on blood vessels that already feed existing tumors. In contrast, VDAs cause the vascular structure inside a solid tumor to collapse, depriving the tumor of blood and oxygen it needs to survive. Therefore, VDAs are an attractive way to approach the cancer problem by combating developed tumors. The following review discusses six small molecule VDAs, namely DMXAA, ZD6126, TZT1027, CA4P, AVE8062, and Oxi4503, their synthesis, biological mechanism of action, and current clinical status.
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Affiliation(s)
- John W Lippert
- Medicinal Chemistry Department, Albany Molecular Research, Inc., PO Box 15098, Albany, NY 12212-5098, USA.
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46
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Huang B, Huffaker TC. Dynamic microtubules are essential for efficient chromosome capture and biorientation in S. cerevisiae. ACTA ACUST UNITED AC 2006; 175:17-23. [PMID: 17030980 PMCID: PMC2064488 DOI: 10.1083/jcb.200606021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Attachment of chromosomes to the mitotic spindle has been proposed to require dynamic microtubules that randomly search three-dimensional space and become stabilized upon capture by kinetochores. In this study, we test this model by examining chromosome capture in Saccharomyces cerevisiae mutants with attenuated microtubule dynamics. Although viable, these cells are slow to progress through mitosis. Preanaphase cells contain a high proportion of chromosomes that are attached to only one spindle pole and missegregate in the absence of the spindle assembly checkpoint. Measurement of the rates of chromosome capture and biorientation demonstrate that both are severely decreased in the mutants. These results provide direct evidence that dynamic microtubules are critical for efficient chromosome capture and biorientation and support the hypothesis that microtubule search and capture plays a central role in assembly of the mitotic spindle.
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Affiliation(s)
- Baoying Huang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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Albee AJ, Tao W, Wiese C. Phosphorylation of maskin by Aurora-A is regulated by RanGTP and importin beta. J Biol Chem 2006; 281:38293-301. [PMID: 17057251 DOI: 10.1074/jbc.m607203200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitotic spindle assembly in Xenopus egg extracts is regulated at least in part by importin beta and its regulator, the small GTPase, Ran. RanGTP stabilizes microtubules near the chromosomes during spindle assembly by selectively releasing spindle assembly factors from inhibition by importin alpha/beta in the vicinity of the chromosomes. Several spindle assembly factors are regulated in this manner. We identified maskin, the Xenopus member of the transforming acidic coiled coil family of proteins, as a potential candidate in a two-step affinity chromatography approach designed to uncover additional downstream targets of importin alpha/beta in mitosis. Here, we show that although maskin lacks a canonical nuclear localization sequence, it binds importin beta in a RanGTP-regulated manner. We further show that importin beta inhibits the regulatory phosphorylation of maskin by Aurora-A. This suggests a novel mechanism by which importin beta regulates the activity of a spindle assembly factor.
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Affiliation(s)
- Alison J Albee
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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48
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Xue GP, McIntyre CL, Chapman S, Bower NI, Way H, Reverter A, Clarke B, Shorter R. Differential gene expression of wheat progeny with contrasting levels of transpiration efficiency. PLANT MOLECULAR BIOLOGY 2006; 61:863-81. [PMID: 16927201 DOI: 10.1007/s11103-006-0055-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 03/27/2006] [Indexed: 05/11/2023]
Abstract
High water use efficiency or transpiration efficiency (TE) in wheat is a desirable physiological trait for increasing grain yield under water-limited environments. The identification of genes associated with this trait would facilitate the selection for genotypes with higher TE using molecular markers. We performed an expression profiling (microarray) analysis of approximately 16,000 unique wheat ESTs to identify genes that were differentially expressed between wheat progeny lines with contrasting TE levels from a cross between Quarrion (high TE) and Genaro 81 (low TE). We also conducted a second microarray analysis to identify genes responsive to drought stress in wheat leaves. Ninety-three genes that were differentially expressed between high and low TE progeny lines were identified. One fifth of these genes were markedly responsive to drought stress. Several potential growth-related regulatory genes, which were down-regulated by drought, were expressed at a higher level in the high TE lines than the low TE lines and are potentially associated with a biomass production component of the Quarrion-derived high TE trait. Eighteen of the TE differentially expressed genes were further analysed using quantitative RT-PCR on a separate set of plant samples from those used for microarray analysis. The expression levels of 11 of the 18 genes were positively correlated with the high TE trait, measured as carbon isotope discrimination (Delta(13)C). These data indicate that some of these TE differentially expressed genes are candidates for investigating processes that underlie the high TE trait or for use as expression quantitative trait loci (eQTLs) for TE.
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Affiliation(s)
- Gang-Ping Xue
- CSIRO Plant Industry, 306 Carmody Road, St Lucia, Qld, 4067, Australia.
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Tsai MY, Zheng Y. Aurora A kinase-coated beads function as microtubule-organizing centers and enhance RanGTP-induced spindle assembly. Curr Biol 2006; 15:2156-63. [PMID: 16332542 DOI: 10.1016/j.cub.2005.10.054] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 09/28/2005] [Accepted: 10/19/2005] [Indexed: 10/25/2022]
Abstract
The roles of the kinase Aurora A (AurA) in centrosome function and spindle assembly have been established in Drosophila, C. elegans, and Xenopus egg extracts . Recently, we have shown that AurA acts downstream of the RanGTPase signaling pathway to stimulate spindle assembly in mitosis . However, it is still not clear whether AurA can stimulate the formation of microtubule organizing centers (MTOC) on its own. Moreover, whether AurA is essential for spindle assembly in the absence of centrosomes has remained unclear . Here, we report the development of functional assays that allow us to show that activation of AurA by TPX2 is essential for Ran-stimulated spindle assembly in the presence or absence of centrosomes. Furthermore, AurA-coated magnetic beads function as MTOCs in the presence of RanGTP in Xenopus egg extracts and RanGTP stimulates AurA to recruit activities responsible for both MT nucleation and organization to the beads. The MTOC function of AurA-coated beads require both MT nucleators and motors. Compared to XMAP215-coated beads , AurA-coated beads increase the rate of bipolar spindle assembly in the presence of RanGTP, and the kinase activity of AurA is essential for the beads to function as MTOCs.
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Affiliation(s)
- Ming-Ying Tsai
- Department of Embryology, Carnegie Institution of Washington and Howard Hughes Medical Institute, Baltimore, Maryland 21218, USA
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Roszko I, Afonso C, Henrique D, Mathis L. Key role played by RhoA in the balance between planar and apico-basal cell divisions in the chick neuroepithelium. Dev Biol 2006; 298:212-24. [PMID: 16860308 DOI: 10.1016/j.ydbio.2006.06.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2006] [Revised: 06/13/2006] [Accepted: 06/15/2006] [Indexed: 10/24/2022]
Abstract
The cell division axis determines the position of daughter cells and is therefore critical for cell fate. During vertebrate neurogenesis, most cell divisions take place within the plane of the neuroepithelium (Das, T., Payer, B., Cayouette, M., and Harris, W.A. (2003). In vivo time-lapse imaging of cell divisions during neurogenesis in the developing zebrafish retina. Neuron 37, 597-609. Haydar, T.F., Ang, E., Jr., and Rakic, P. (2003). Mitotic spindle rotation and mode of cell division in the developing telencephalon. Proc Natl Acad Sci U S A 100, 2890-5. Kosodo, Y., Roper, K., Haubensak, W., Marzesco, A. M., Corbeil, D., and Huttner, W. B. (2004). Asymmetric distribution of the apical plasma membrane during neurogenic divisions of mammalian neuroepithelial cells. EMBO J. 23, 2314-24). The cellular constraints responsible for this preferential orientation are poorly understood. Combining electroporation and time-lapse confocal imaging of chick neural progenitors, the events responsible for positioning the mitotic spindle and their dependence on RhoA were investigated. The results indicate that the spindle forms with a random orientation. However, the final orientation of cell divisions is dependent on two main factors: (i) an early rotation of the spindle that aligns it within the plane of the neuroepithelium, and (ii) a specific limitation of spindle oscillations, despite free rotation around the apico-basal axis. Expressing a dominant-negative RhoA leads to apico-basal cell divisions after a correct initial rotation of the spindle. Our data reveal a specific role for RhoA in the maintenance of spindle orientation, prior to anaphase. Thus, RhoA could be a key player potentially regulated by the neurogenic program or by the neural stem cell environment to control the balance between planar and apico-basal divisions, during normal or pathological development.
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Affiliation(s)
- I Roszko
- Unité de Biologie Moléculaire du Développement, CNRS URA 2578, Institut Pasteur, 25, rue du Docteur Roux, 75724 Paris Cedex 15, France
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