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Li DZ, Yang ZY, Leng A, Zhang Q, Zhang XD, Bian YC, Xiao R, Ren JJ. Targeting AGTPBP1 inhibits pancreatic cancer progression via regulating microtubules and ERK signaling pathway. Mol Med 2024; 30:119. [PMID: 39129004 PMCID: PMC11318240 DOI: 10.1186/s10020-024-00892-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 08/05/2024] [Indexed: 08/13/2024] Open
Abstract
BACKGROUND AGTPBP1 is a cytosolic carboxypeptidase that cleaves poly-glutamic acids from the C terminus or side chains of α/β tubulins. Although its dysregulated expression has been linked to the development of non-small cell lung cancer, the specific roles and mechanisms of AGTPBP1 in pancreatic cancer (PC) have yet to be fully understood. In this study, we examined the role of AGTPBP1 on PC in vitro and in vivo. METHODS Immunohistochemistry was used to examine the expression of AGTPBP1 in PC and non-cancerous tissues. Additionally, we assessed the malignant behaviors of PC cells following siRNA-mediated AGTPBP1 knockdown both in vitro and in vivo. RNA sequencing and bioinformatics analysis were performed to identify the differentially expressed genes regulated by AGTPBP1. RESULTS We determined that AGTPBP1 was overexpressed in PC tissues and the higher expression of AGTPBP1 was closely related to the location of tumors. AGTPBP1 inhibition can significantly decrease cell progression in vivo and in vitro. Moreover, the knockdown of AGTPBP1 inhibited the expression of ERK1/2, P-ERK1/2, MYLK, and TUBB4B proteins via the ERK signaling pathway. CONCLUSION Our research indicates that AGTPBP1 may be a putative therapeutic target for PC.
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Affiliation(s)
- Ding-Zhong Li
- Department of Hepatobiliary, Pancreatic and Splenic Surgery, The Affiliated Hospital of Inner Mongolia Medical University, #1, Tongdao North Street, Huhhot, 010051, PR China
| | - Zhe-Yu Yang
- Department of Hepatobiliary, Pancreatic and Splenic Surgery, The Affiliated Hospital of Inner Mongolia Medical University, #1, Tongdao North Street, Huhhot, 010051, PR China
| | - Asi Leng
- Medical Simulation Center, Inner Mongolia Medical University, Huhhot, 010059, PR China
| | - Qian Zhang
- Department of Hepatobiliary, Pancreatic and Splenic Surgery, The Affiliated Hospital of Inner Mongolia Medical University, #1, Tongdao North Street, Huhhot, 010051, PR China
| | - Xiao-Dong Zhang
- Department of Hepatobiliary, Pancreatic and Splenic Surgery, The Affiliated Hospital of Inner Mongolia Medical University, #1, Tongdao North Street, Huhhot, 010051, PR China
| | - Yan-Chao Bian
- Inner Mongolia Key Laboratory of Molecular Pathology, Inner Mongolia Medical University, #5, Xin Hua Street, Huhhot, 010059, PR China
| | - Rui Xiao
- Inner Mongolia Key Laboratory of Molecular Pathology, Inner Mongolia Medical University, #5, Xin Hua Street, Huhhot, 010059, PR China.
| | - Jian-Jun Ren
- Department of Hepatobiliary, Pancreatic and Splenic Surgery, The Affiliated Hospital of Inner Mongolia Medical University, #1, Tongdao North Street, Huhhot, 010051, PR China.
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2
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Kar S, Mukherjee R, Guha S, Talukdar D, Das G, Murmu N. Modulating the acetylation of α-tubulin by LncRNAs and microRNAs helps in the progression of cancer. Cell Biochem Funct 2024; 42:e3953. [PMID: 38414166 DOI: 10.1002/cbf.3953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/20/2024] [Accepted: 02/06/2024] [Indexed: 02/29/2024]
Abstract
Malignant tumor cells go through morphological and gene expression alterations, including rearrangement of cytoskeleton proteins that promote invasion and metastasis. Microtubules form a major cytoskeleton component that plays a significant role in regulating multiple cellular activities and function depending on the presence of posttranslational modification (PTM). Acetylation is a type of PTM that generally occurs in the lysine 40 region of α-tubulin and is known to be critically associated with cancer metastasis. Current evidence demonstrates that noncoding RNAs, such as long noncoding RNA (lncRNA) and microRNA (or miRNA), which are correlated with gene regulation modulate the expression of acetylated tubulin in the development and metastasis of cancer. This review provides an overview about the role of lncRNA and miRNA in regulation of tubulin acetylation in various types of cancer.
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Affiliation(s)
- Sneha Kar
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
| | - Rimi Mukherjee
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
| | - Subhabrata Guha
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
| | - Debojit Talukdar
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
| | - Gaurav Das
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
| | - Nabendu Murmu
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, India
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Costa G, Ribeiro FF, Sebastião AM, Muir EM, Vaz SH. Bridging the gap of axonal regeneration in the central nervous system: A state of the art review on central axonal regeneration. Front Neurosci 2022; 16:1003145. [PMID: 36440273 PMCID: PMC9682039 DOI: 10.3389/fnins.2022.1003145] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 10/19/2022] [Indexed: 08/26/2023] Open
Abstract
Neuronal regeneration in the central nervous system (CNS) is an important field of research with relevance to all types of neuronal injuries, including neurodegenerative diseases. The glial scar is a result of the astrocyte response to CNS injury. It is made up of many components creating a complex environment in which astrocytes play various key roles. The glial scar is heterogeneous, diverse and its composition depends upon the injury type and location. The heterogeneity of the glial scar observed in different situations of CNS damage and the consequent implications for axon regeneration have not been reviewed in depth. The gap in this knowledge will be addressed in this review which will also focus on our current understanding of central axonal regeneration and the molecular mechanisms involved. The multifactorial context of CNS regeneration is discussed, and we review newly identified roles for components previously thought to solely play an inhibitory role in central regeneration: astrocytes and p75NTR and discuss their potential and relevance for deciding therapeutic interventions. The article ends with a comprehensive review of promising new therapeutic targets identified for axonal regeneration in CNS and a discussion of novel ways of looking at therapeutic interventions for several brain diseases and injuries.
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Affiliation(s)
- Gonçalo Costa
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - Filipa F. Ribeiro
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Ana M. Sebastião
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Elizabeth M. Muir
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Sandra H. Vaz
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
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4
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Sen S, Lagas S, Roy A, Kumar H. Cytoskeleton saga: Its regulation in normal physiology and modulation in neurodegenerative disorders. Eur J Pharmacol 2022; 925:175001. [PMID: 35525310 DOI: 10.1016/j.ejphar.2022.175001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/31/2022] [Accepted: 04/29/2022] [Indexed: 11/25/2022]
Abstract
Cells are fundamental units of life. To ensure the maintenance of homeostasis, integrity of structural and functional counterparts is needed to be essentially balanced. The cytoskeleton plays a vital role in regulating the cellular morphology, signalling and other factors involved in pathological conditions. Microtubules, actin (microfilaments), intermediate filaments (IF) and their interactions are required for these activities. Various proteins associated with these components are primary requirements for directing their functions. Disruption of this organization due to faulty genetics, oxidative stress or impaired transport mechanisms are the major causes of dysregulated signalling cascades leading to various pathological conditions like Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD) or amyotrophic lateral sclerosis (ALS), hereditary spastic paraplegia (HSP) or any traumatic injury like spinal cord injury (SCI). Novel or conventional therapeutic approaches may be specific or non-specific, targeting either three basic components of the cytoskeleton or various cascades that serve as a cue to numerous pathways like ROCK signalling or the GSK-3β pathway. An enormous number of drugs have been redirected for modulating the cytoskeletal dynamics and thereby may pave the way for inhibiting the progression of these diseases and their complications.
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Affiliation(s)
- Santimoy Sen
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Sheetal Lagas
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Abhishek Roy
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Hemant Kumar
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India.
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Nurieva EV, Zefirov NA, Temnyakova NS, Kuznetsov SA, Zefirova ON. C(7)-Derivatives of colchicine with guanosine and biphenyl moieties: molecular modeling, synthesis, and tubulin clustering effect in cancer cells. Russ Chem Bull 2020. [DOI: 10.1007/s11172-020-3025-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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6
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Vukušić K, Buđa R, Tolić IM. Force-generating mechanisms of anaphase in human cells. J Cell Sci 2019; 132:132/18/jcs231985. [DOI: 10.1242/jcs.231985] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ABSTRACT
What forces drive chromosome segregation remains one of the most challenging questions in cell division. Even though the duration of anaphase is short, it is of utmost importance for genome fidelity that no mistakes are made. Seminal studies in model organisms have revealed different mechanisms operating during chromosome segregation in anaphase, but the translation of these mechanisms to human cells is not straightforward. Recent work has shown that kinetochore fiber depolymerization during anaphase A is largely motor independent, whereas spindle elongation during anaphase B is coupled to sliding of interpolar microtubules in human cells. In this Review, we discuss the current knowledge on the mechanisms of force generation by kinetochore, interpolar and astral microtubules. By combining results from numerous studies, we propose a comprehensive picture of the role of individual force-producing and -regulating proteins. Finally, by linking key concepts of anaphase to most recent data, we summarize the contribution of all proposed mechanisms to chromosome segregation and argue that sliding of interpolar microtubules and depolymerization at the kinetochore are the main drivers of chromosome segregation during early anaphase in human cells.
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Affiliation(s)
- Kruno Vukušić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Renata Buđa
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Iva M. Tolić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
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7
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Rodríguez‐Sevilla P, Sanz‐Rodríguez F, Peláez RP, Delgado‐Buscalioni R, Liang L, Liu X, Jaque D. Upconverting Nanorockers for Intracellular Viscosity Measurements During Chemotherapy. ACTA ACUST UNITED AC 2019; 3:e1900082. [DOI: 10.1002/adbi.201900082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/22/2019] [Indexed: 11/06/2022]
Affiliation(s)
| | - Francisco Sanz‐Rodríguez
- Fluorescence Imaging Group Departamento de Biología Facultad de CienciasUniversidad Autónoma de Madrid 28049 Madrid Spain
- Nanobiology GroupInstituto Ramón y Cajal de Investigación Sanitaria Hospital Ramón y Cajal. Ctra. De Colmenar Viejo Km. 9100 28034 Madrid Spain
| | - Raúl P. Peláez
- Departamento de Física Teórica de la Materia Condensada Facultad de CienciasUniversidad Autónoma de Madrid 28049 Madrid Spain
| | - Rafael Delgado‐Buscalioni
- Departamento de Física Teórica de la Materia Condensada Facultad de CienciasUniversidad Autónoma de Madrid 28049 Madrid Spain
| | - Liangliang Liang
- Department of ChemistryNational University of Singapore Science Drive 3 Singapore 117543 Singapore
| | - Xiaogang Liu
- Department of ChemistryNational University of Singapore Science Drive 3 Singapore 117543 Singapore
| | - Daniel Jaque
- Nanobiology GroupInstituto Ramón y Cajal de Investigación Sanitaria Hospital Ramón y Cajal. Ctra. De Colmenar Viejo Km. 9100 28034 Madrid Spain
- Fluorescence Imaging Group Departamento de Fisica de MaterialesUniversidad Autónoma de Madrid 28049 Madrid Spain
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8
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Tubulin heterogeneity regulates functions and dynamics of microtubules and plays a role in the development of drug resistance in cancer. Biochem J 2019; 476:1359-1376. [DOI: 10.1042/bcj20190123] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 04/21/2019] [Accepted: 04/24/2019] [Indexed: 01/01/2023]
Abstract
Abstract
Microtubules, composed of αβ-tubulin heterodimers, exhibit diverse structural and functional properties in different cell types. The diversity in the microtubule structure originates from tubulin heterogeneities, namely tubulin isotypes and their post-translational modifications (PTMs). These heterogeneities confer differential stability to microtubules and provide spatial cues for the functioning of the cell. Furthermore, the altered expressions of tubulin isotypes and PTMs are prominent factors for the development of resistance against some cancer drugs. In this review, we summarize our current knowledge of the tubulin isotypes and PTMs and how, together, they control the cellular functions of the microtubules. We also describe how cancer cells use this tubulin heterogeneity to acquire resistance against clinical agents and discuss existing attempts to counter the developed resistance.
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9
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Chu S, Baker MR, Leong G, Letcher RJ, Li QX. Covalent binding of the organophosphate insecticide profenofos to tyrosine on α- and β-tubulin proteins. CHEMOSPHERE 2018; 199:154-159. [PMID: 29433029 PMCID: PMC5847477 DOI: 10.1016/j.chemosphere.2018.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 01/31/2018] [Accepted: 02/01/2018] [Indexed: 06/08/2023]
Abstract
Organophosphorus (OP) compounds can bind covalently to many types of proteins and form protein adducts. These protein adducts can indicate the exposure to and neurotoxicity of OPs. In the present work, we studied adduction of tubulin with the OP insecticide profenofos in vitro and optimized the method for detection of adducted peptides. Porcine tubulin was incubated with profenofos and was then digested with trypsin, followed by mass spectrometric identification of the profenofos-modified tubulin and binding sites. With solvent-assisted digestion (80% acetonitrile in digestion solution), the protein was digested for peptide identification, especially for some peptides with low mass. The MALDI-TOF-MS and LC-ESI-TOF-MS analysis results showed that profenofos bound covalently to Tyr83 in porcine α-tubulin (TGTY*83R) and to Tyr281 in porcine β-tubulin (GSQQY*281R) with a mass increase of 166.02 Da from the original peptide fragments of porcine tubulin proteins. Tyrosine adduct sites were also confirmed by MALDI-TOF/TOF-MS analysis. This result may partially explain the neurotoxicity of profenofos at low doses and prolonged periods of exposure.
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Affiliation(s)
- Shaogang Chu
- Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Science Directorate, National Wildlife Research Centre, Environment and Climate Change Canada, 1125 Colonel By Dr., Carleton University, Ottawa, ON, K1A 0H3, Canada
| | - Margaret R Baker
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, 1955 East West Road, Honolulu, HI, 96822, USA
| | - Gladys Leong
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, 1955 East West Road, Honolulu, HI, 96822, USA
| | - Robert J Letcher
- Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Science Directorate, National Wildlife Research Centre, Environment and Climate Change Canada, 1125 Colonel By Dr., Carleton University, Ottawa, ON, K1A 0H3, Canada
| | - Qing X Li
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, 1955 East West Road, Honolulu, HI, 96822, USA.
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10
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Majumdar S, Ghosh Dastidar S. Ligand Binding Swaps between Soft Internal Modes of α,β-Tubulin and Alters Its Accessible Conformational Space. J Phys Chem B 2016; 121:118-128. [DOI: 10.1021/acs.jpcb.6b11322] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sarmistha Majumdar
- Bioinformatics Centre, Bose Institute, P-1/12 C.I.T. Scheme VII M, Kolkata 700054, India
| | - Shubhra Ghosh Dastidar
- Bioinformatics Centre, Bose Institute, P-1/12 C.I.T. Scheme VII M, Kolkata 700054, India
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11
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Recent advances in design, synthesis and bioactivity of paclitaxel-mimics. Fitoterapia 2016; 110:26-37. [DOI: 10.1016/j.fitote.2016.02.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/17/2016] [Accepted: 02/18/2016] [Indexed: 11/18/2022]
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12
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Barata JF, Zamarrón A, Neves MGP, Faustino MAF, Tomé AC, Cavaleiro JA, Röder B, Juarranz Á, Sanz-Rodríguez F. Photodynamic effects induced by meso-tris(pentafluorophenyl)corrole and its cyclodextrin conjugates on cytoskeletal components of HeLa cells. Eur J Med Chem 2015; 92:135-44. [DOI: 10.1016/j.ejmech.2014.12.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 12/12/2014] [Accepted: 12/13/2014] [Indexed: 01/28/2023]
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13
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Abstract
Axon regeneration after damage is widespread in the animal kingdom, and the nematode Caenorhabditis elegans has recently emerged as a tractable model in which to study the genetics and cell biology of axon regrowth in vivo. A key early step in axon regrowth is the conversion of part of a mature axon shaft into a growth cone-like structure, involving coordinated alterations in the microtubule, actin, and neurofilament systems. Recent attention has focused on microtubule dynamics as a determinant of axon-regrowth ability in several organisms. Live imaging studies have begun to reveal how the microtubule cytoskeleton is remodeled after axon injury, as well as the regulatory pathways involved. The dual leucine zipper kinase family of mixed-lineage kinases has emerged as a critical sensor of axon damage and plays a key role in regulating microtubule dynamics in the damaged axon.
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Affiliation(s)
- Andrew D Chisholm
- Division of Biological Sciences, Section of Neurobiology, University of California, San Diego, La Jolla, California 92093;
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14
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Vitriol EA, Zheng JQ. Growth cone travel in space and time: the cellular ensemble of cytoskeleton, adhesion, and membrane. Neuron 2012; 73:1068-81. [PMID: 22445336 DOI: 10.1016/j.neuron.2012.03.005] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2012] [Indexed: 10/28/2022]
Abstract
Growth cones, found at the tip of axonal projections, are the sensory and motile organelles of developing neurons that enable axon pathfinding and target recognition for precise wiring of the neural circuitry. To date, many families of conserved guidance molecules and their corresponding receptors have been identified that work in space and time to ensure billions of axons to reach their targets. Research in the past two decades has also gained significant insight into the ways in which growth cones translate extracellular signals into directional migration. This review aims to examine new progress toward understanding the cellular mechanisms underlying directional motility of the growth cone and to discuss questions that remain to be addressed. Specifically, we will focus on the cellular ensemble of cytoskeleton, adhesion, and membrane and examine how the intricate interplay between these processes orchestrates the directed movement of growth cones.
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Affiliation(s)
- Eric A Vitriol
- Department of Cell Biology and Neurology, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322, USA
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15
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KAPOOR SONIA, RANJITH P, PANDA DULAL. ENGINEERING AND THERAPEUTIC APPLICATIONS OF MICROTUBULES. INTERNATIONAL JOURNAL OF NANOSCIENCE 2011. [DOI: 10.1142/s0219581x11009325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Living organisms are fascinating systems. The macromolecules that make up a living cell possess equally astounding structural and functional characteristics. By taking simple cues from how these biopolymers organize and work inside the cell, one can draw inspiration to utilize them outside their natural environment for several purposes. Microtubules are example of biopolymers that demonstrate extraordinary properties of hierarchical self-organization, dynamic remodeling and mechanical rigidity. Mimicking the principles and properties of microtubules and improving them have opened novel engineering avenues. In addition, due to the functions that microtubules perform during cell division, they are excellent therapeutic drug targets for anticancer agents. In this work, we describe the biological properties and functions of microtubules, and discuss their engineering and therapeutic applications.
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Affiliation(s)
- SONIA KAPOOR
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - P. RANJITH
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - DULAL PANDA
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
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16
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Abstract
The mechanisms that move chromatids poleward during anaphase A have fascinated researchers for decades. There is now growing evidence that this movement is tightly linked to the active depolymerization of both ends of kinetochore-associated microtubules, a mechanism we refer to as "Pacman-Flux." Contemporary data suggest that this is catalyzed by the integration of multiple enzymatic activities including (1) microtubule-end depolymerases housed at the pole or kinetochore, (2) microtubule-severing enzymes used to uncap the ends of kinetochore-associated microtubules, and (3) molecular motors which drive tubulins towards the pole or into kinetochores.
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17
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Macroscopic simulations of microtubule dynamics predict two steady-state processes governing array morphology. Comput Biol Chem 2011; 35:269-81. [PMID: 22000798 DOI: 10.1016/j.compbiolchem.2011.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/10/2011] [Accepted: 06/17/2011] [Indexed: 01/21/2023]
Abstract
Microtubule polymers typically function through their collective organization into a patterned array. The formation of the pattern, whether it is a relatively simple astral array or a highly complex mitotic spindle, relies on controlled microtubule nucleation and the basal dynamics parameters governing polymer growth and shortening. We have investigated the interaction between the microtubule nucleation and dynamics parameters, using macroscopic Monte Carlo simulations, to determine how these parameters contribute to the underlying microtubule array morphology (i.e. polymer density and length distribution). In addition to the well-characterized steady state achieved between free tubulin subunits and microtubule polymer, we propose that microtubule nucleation and extinction constitute a second, interdependent steady state process. Our simulation studies show that the magnitude of both nucleation and extinction additively impacts the final steady state free subunit concentration. We systematically varied individual microtubule dynamics parameters to survey the effects on array morphology and find specific sensitivity to perturbations of catastrophe frequency. Altering the cellular context for the microtubule array, we find that nucleation template number plays a defining role in shaping the microtubule length distribution and polymer density.
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Stanton RA, Gernert KM, Nettles JH, Aneja R. Drugs that target dynamic microtubules: a new molecular perspective. Med Res Rev 2011; 31:443-81. [PMID: 21381049 DOI: 10.1002/med.20242] [Citation(s) in RCA: 387] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Microtubules have long been considered an ideal target for anticancer drugs because of the essential role they play in mitosis, forming the dynamic spindle apparatus. As such, there is a wide variety of compounds currently in clinical use and in development that act as antimitotic agents by altering microtubule dynamics. Although these diverse molecules are known to affect microtubule dynamics upon binding to one of the three established drug domains (taxane, vinca alkaloid, or colchicine site), the exact mechanism by which each drug works is still an area of intense speculation and research. In this study, we review the effects of microtubule-binding chemotherapeutic agents from a new perspective, considering how their mode of binding induces conformational changes and alters biological function relative to the molecular vectors of microtubule assembly or disassembly. These "biological vectors" can thus be used as a spatiotemporal context to describe molecular mechanisms by which microtubule-targeting drugs work.
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19
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Malcos JL, Hancock WO. Engineering tubulin: microtubule functionalization approaches for nanoscale device applications. Appl Microbiol Biotechnol 2011; 90:1-10. [PMID: 21327409 DOI: 10.1007/s00253-011-3140-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 01/05/2011] [Accepted: 01/05/2011] [Indexed: 11/28/2022]
Abstract
With the emergences of engineered devices at microscale and nanoscale dimensions, there is a growing need for controlled actuation and transport at these length scales. The kinesin-microtubule system provides a highly evolved biological transport system well suited for these tasks. Accordingly, there is an ongoing effort to create hybrid nanodevices that integrate biological components with engineered materials for applications such as biological separations, nanoscale assembly, and sensing. Adopting microtubules for these applications generally requires covalent attachment of biotin, fluorophores, or other biomolecules to tubulin enable surface or cargo attachment, or visualization. This review summarizes different strategies for functionalizing microtubules for application-focused as well as basic biological research. These functionalization strategies must maintain the integrity of microtubule proteins so that they do not depolymerize and can be transported by kinesin motors, while adding utility such as the ability to reversibly bind cargo. The relevant biochemical and electrical properties of microtubules are discussed, as well as strategies for microtubule stabilization and long-term storage. Next, attachment strategies, such as antibodies and DNA hybridization that have proven useful to date, are discussed in the context of ongoing hybrid nanodevice research. The review concludes with a discussion of less explored opportunities, such as harnessing the utility of tubulin posttranslational modifications and the use of recombinant tubulin that may enable future progress in nanodevice development.
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Affiliation(s)
- Jennelle L Malcos
- Department of Biology, The Pennsylvania State University, 208 Muller Lab, University Park, PA 16802, USA
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Maiato H, Lince-Faria M. The perpetual movements of anaphase. Cell Mol Life Sci 2010; 67:2251-69. [PMID: 20306325 PMCID: PMC11115923 DOI: 10.1007/s00018-010-0327-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 12/29/2022]
Abstract
One of the most extraordinary events in the lifetime of a cell is the coordinated separation of sister chromatids during cell division. This is truly the essence of the entire mitotic process and the reason for the most profound morphological changes in cytoskeleton and nuclear organization that a cell may ever experience. It all occurs within a very short time window known as "anaphase", as if the cell had spent the rest of its existence getting ready for this moment in an ultimate act of survival. And there is a good reason for this: no space for mistakes. Problems in the distribution of chromosomes during cell division have been correlated with aneuploidy, a common feature observed in cancers and several birth defects, and the main cause of spontaneous abortion in humans. In this paper, we critically review the mechanisms of anaphase chromosome motion that resisted the scrutiny of more than 100 years of research, as part of a tribute to the pioneering work of Miguel Mota.
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Affiliation(s)
- Helder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal.
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21
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Griseofulvin stabilizes microtubule dynamics, activates p53 and inhibits the proliferation of MCF-7 cells synergistically with vinblastine. BMC Cancer 2010; 10:213. [PMID: 20482847 PMCID: PMC2885362 DOI: 10.1186/1471-2407-10-213] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 05/19/2010] [Indexed: 11/10/2022] Open
Abstract
Background Griseofulvin, an antifungal drug, has recently been shown to inhibit proliferation of various types of cancer cells and to inhibit tumor growth in athymic mice. Due to its low toxicity, griseofulvin has drawn considerable attention for its potential use in cancer chemotherapy. This work aims to understand how griseofulvin suppresses microtubule dynamics in living cells and sought to elucidate the antimitotic and antiproliferative action of the drug. Methods The effects of griseofulvin on the dynamics of individual microtubules in live MCF-7 cells were measured by confocal microscopy. Immunofluorescence microscopy, western blotting and flow cytometry were used to analyze the effects of griseofulvin on spindle microtubule organization, cell cycle progression and apoptosis. Further, interactions of purified tubulin with griseofulvin were studied in vitro by spectrophotometry and spectrofluorimetry. Docking analysis was performed using autodock4 and LigandFit module of Discovery Studio 2.1. Results Griseofulvin strongly suppressed the dynamic instability of individual microtubules in live MCF-7 cells by reducing the rate and extent of the growing and shortening phases. At or near half-maximal proliferation inhibitory concentration, griseofulvin dampened the dynamicity of microtubules in MCF-7 cells without significantly disrupting the microtubule network. Griseofulvin-induced mitotic arrest was associated with several mitotic abnormalities like misaligned chromosomes, multipolar spindles, misegregated chromosomes resulting in cells containing fragmented nuclei. These fragmented nuclei were found to contain increased concentration of p53. Using both computational and experimental approaches, we provided evidence suggesting that griseofulvin binds to tubulin in two different sites; one site overlaps with the paclitaxel binding site while the second site is located at the αβ intra-dimer interface. In combination studies, griseofulvin and vinblastine were found to exert synergistic effects against MCF-7 cell proliferation. Conclusions The study provided evidence suggesting that griseofulvin shares its binding site in tubulin with paclitaxel and kinetically suppresses microtubule dynamics in a similar manner. The results revealed the antimitotic mechanism of action of griseofulvin and provided evidence suggesting that griseofulvin alone and/or in combination with vinblastine may have promising role in breast cancer chemotherapy.
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Ikeda K, Semenova I, Zhapparova O, Rodionov V. Melanophores for microtubule dynamics and motility assays. Methods Cell Biol 2010; 97:401-14. [PMID: 20719282 DOI: 10.1016/s0091-679x(10)97021-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Microtubules (MTs) are cytoskeletal structures essential for cell division, locomotion, intracellular transport, and spatial organization of the cytoplasm. In most interphase cells, MTs are organized into a polarized radial array with minus-ends clustered at the centrosome and plus-ends extended to the cell periphery. This array directs transport of organelles driven by MT-based motor proteins that specifically move either to plus- or to minus-ends. Along with using MTs as tracks for cargo, motor proteins can organize MTs into a radial array in the absence of the centrosome. Transport of organelles and motor-dependent radial organization of MTs require MT dynamics, continuous addition and loss of tubulin subunits at minus- and plus-ends. A unique experimental system for studying the role of MT dynamics in these processes is the melanophore, which provides a useful tool for imaging of both dynamic MTs and moving membrane organelles. Melanophores are filled with pigment granules that are synchronously transported by motor proteins in response to hormonal stimuli. The flat shape of the cell and the radial organization of MTs facilitate imaging of dynamic MT plus-ends and monitoring of their interaction with membrane organelles. Microsurgically produced cytoplasmic fragments of melanophores are used to study the centrosome-independent rearrangement of MTs into a radial array. Here we describe the experimental approaches to study the role of MT dynamics in intracellular transport and centrosome-independent MT organization in melanophores. We focus on the preparation of cell cultures, microsurgery and microinjection, fluorescence labeling, and live imaging of MTs.
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Affiliation(s)
- Kazuho Ikeda
- Department of Cell Biology, R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut 06032-1507, USA
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23
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Hinow P, Rezania V, Tuszyński JA. Continuous model for microtubule dynamics with catastrophe, rescue, and nucleation processes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:031904. [PMID: 19905143 DOI: 10.1103/physreve.80.031904] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 05/14/2009] [Indexed: 05/28/2023]
Abstract
Microtubules are a major component of the cytoskeleton distinguished by highly dynamic behavior both in vitro and in vivo referred to as dynamic instability. We propose a general mathematical model that accounts for the growth, catastrophe, rescue, and nucleation processes in the polymerization of microtubules from tubulin dimers. Our model is an extension of various mathematical models developed earlier formulated in order to capture and unify the various aspects of tubulin polymerization. While attempting to use a minimal number of adjustable parameters, the proposed model covers a broad range of behaviors and has predictive features discussed in the paper. We have analyzed the range of resultant dynamical behavior of the microtubules by changing each of the parameter values at a time and observing the emergence of various dynamical regimes that agree well with the previously reported experimental data and behavior.
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Affiliation(s)
- Peter Hinow
- Institute for Mathematics and its Applications, University of Minnesota, 114 Lind Hall, Minneapolis, Minnesota 55455, USA.
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24
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Fabian L, Troscianczuk J, Forer A. Calyculin A, an enhancer of myosin, speeds up anaphase chromosome movement. CELL & CHROMOSOME 2007; 6:1. [PMID: 17381845 PMCID: PMC1847834 DOI: 10.1186/1475-9268-6-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Accepted: 03/24/2007] [Indexed: 12/23/2022]
Abstract
Actin and myosin inhibitors often blocked anaphase movements in insect spermatocytes in previous experiments. Here we treat cells with an enhancer of myosin, Calyculin A, which inhibits myosin-light-chain phosphatase from dephosphorylating myosin; myosin thus is hyperactivated. Calyculin A causes anaphase crane-fly spermatocyte chromosomes to accelerate poleward; after they reach the poles they often move back toward the equator. When added during metaphase, chromosomes at anaphase move faster than normal. Calyculin A causes prometaphase chromosomes to move rapidly up and back along the spindle axis, and to rotate. Immunofluorescence staining with an antibody against phosphorylated myosin regulatory light chain (p-squash) indicated increased phosphorylation of cleavage furrow myosin compared to control cells, indicating that calyculin A indeed increased myosin phosphorylation. To test whether the Calyculin A effects are due to myosin phosphatase or to type 2 phosphatases, we treated cells with okadaic acid, which inhibits protein phosphatase 2A at concentrations similar to Calyculin A but requires much higher concentrations to inhibit myosin phosphatase. Okadaic acid had no effect on chromosome movement. Backward movements did not require myosin or actin since they were not affected by 2,3-butanedione monoxime or LatruculinB. Calyculin A affects the distribution and organization of spindle microtubules, spindle actin, cortical actin and putative spindle matrix proteins skeletor and titin, as visualized using immunofluorescence. We discuss how accelerated and backwards movements might arise.
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Affiliation(s)
- Lacramioara Fabian
- Department of Biology, York University, Toronto, Ontario, M3J 1P3, Canada
| | | | - Arthur Forer
- Department of Biology, York University, Toronto, Ontario, M3J 1P3, Canada
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25
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Johansen KM, Johansen J. Cell and Molecular Biology of the Spindle Matrix. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 263:155-206. [PMID: 17725967 DOI: 10.1016/s0074-7696(07)63004-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The concept of a spindle matrix has long been proposed to account for incompletely understood features of microtubule spindle dynamics and force production during mitosis. In its simplest formulation, the spindle matrix is hypothesized to provide a stationary or elastic molecular matrix that can provide a substrate for motor molecules to interact with during microtubule sliding and which can stabilize the spindle during force production. Although this is an attractive concept with the potential to greatly simplify current models of microtubule spindle behavior, definitive evidence for the molecular nature of a spindle matrix or for its direct role in microtubule spindle function has been lagging. However, as reviewed here multiple studies spanning the evolutionary spectrum from lower eukaryotes to vertebrates have provided new and intriguing evidence that a spindle matrix may be a general feature of mitosis.
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Affiliation(s)
- Kristen M Johansen
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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26
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Affiliation(s)
- E Karsenti
- Cell Biology Program, EMBL, Meyerhofstrasse 1 Heidelberg, D-6900, Germany
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Anderson DE, Gueiros-Filho FJ, Erickson HP. Assembly dynamics of FtsZ rings in Bacillus subtilis and Escherichia coli and effects of FtsZ-regulating proteins. J Bacteriol 2004; 186:5775-81. [PMID: 15317782 PMCID: PMC516820 DOI: 10.1128/jb.186.17.5775-5781.2004] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
FtsZ is the major cytoskeletal component of the bacterial cell division machinery. It forms a ring-shaped structure (the Z ring) that constricts as the bacterium divides. Previous in vivo experiments with green fluorescent protein-labeled FtsZ and fluorescence recovery after photobleaching have shown that the Escherichia coli Z ring is extremely dynamic, continually remodeling itself with a half time of 30 s, similar to microtubules in the mitotic spindle. In the present work, under different experimental conditions, we have found that the half time for fluorescence recovery of E. coli Z rings is even shorter (approximately 9 s). As before, the turnover appears to be coupled to GTP hydrolysis, since the mutant FtsZ84 protein, with reduced GTPase in vitro, showed an approximately 3-fold longer half time. We have also extended the studies to Bacillus subtilis and found that this species exhibits equally rapid dynamics of the Z ring (half time, approximately 8 s). Interestingly, null mutations of the FtsZ-regulating proteins ZapA, EzrA, and MinCD had only modest effects on the assembly dynamics. This suggests that these proteins do not directly regulate FtsZ subunit exchange in and out of polymers. In B. subtilis, only 30 to 35% of the FtsZ protein was in the Z ring, from which we conclude that a Z ring only 2 or 3 protofilaments thick can function for cell division.
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Affiliation(s)
- David E Anderson
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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28
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Forer A, Spurck T, Pickett-Heaps JD, Wilson PJ. Structure of kinetochore fibres in crane-fly spermatocytes after irradiation with an ultraviolet microbeam: Neither microtubules nor actin filaments remain in the irradiated region. ACTA ACUST UNITED AC 2003; 56:173-92. [PMID: 14569597 DOI: 10.1002/cm.10144] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We studied chromosome movement after kinetochore microtubules were severed. Severing a kinetochore fibre in living crane-fly spermatocytes with an ultraviolet microbeam creates a kinetochore stub, a birefringent remnant of the spindle fibre connected to the kinetochore and extending only to the edge of the irradiated region. After the irradiation, anaphase chromosomes either move poleward led by their stubs or temporarily stop moving. We examined actin and/or microtubules in irradiated cells by means of confocal fluorescence microscopy or serial-section reconstructions from electron microscopy. For each cell thus examined, chromosome movement had been recorded continuously until the moment of fixation. Kinetochore microtubules were completely severed by the ultraviolet microbeam in cells in which chromosomes continued to move poleward after the irradiation: none were seen in the irradiated regions. Similarly, actin filaments normally present in kinetochore fibres were severed by the ultraviolet microbeam irradiations: the irradiated regions contained no actin filaments and only local spots of non-filamentous actin. There was no difference in irradiated regions when the associated chromosomes continued to move versus when they stopped moving. Thus, one cannot explain motion with severed kinetochore microtubules in terms of either microtubules or actin-filaments bridging the irradiated region. The data seem to negate current models for anaphase chromosome movement and support a model in which poleward chromosome movement results from forces generated within the spindle matrix that propel kinetochore fibres or kinetochore stubs poleward.
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Affiliation(s)
- Arthur Forer
- Biology Department, York University, Toronto, Ontario, Canada.
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29
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Howarth J, Kenny P, McDonnell S, O'Connor A. The design and synthesis of guanosine compounds with in vitro activity against the colon cancer cell line SW480: non-taxane derived mimics of taxol? Bioorg Med Chem Lett 2003; 13:2693-7. [PMID: 12873496 DOI: 10.1016/s0960-894x(03)00543-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the course of our investigation into the use of taxol as a lead compound to design new molecules with anti-cancer activity, we have synthesized four compounds based on protected guanosine coupled to taxol isoserine side-chain analogues. These analogues show in vitro anti-cancer activity against the colon cancer cell line SW480 that their constituent parts do not.
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Affiliation(s)
- Joshua Howarth
- School of Chemical Sciences, Dublin City University, Dublin 9, Ireland.
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Jung YJ, Isaacs JS, Lee S, Trepel J, Neckers L. Microtubule disruption utilizes an NFkappa B-dependent pathway to stabilize HIF-1alpha protein. J Biol Chem 2003; 278:7445-52. [PMID: 12488445 DOI: 10.1074/jbc.m209804200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hypoxia-inducible factor (HIF)-1alpha levels are elevated in normoxic cells undergoing physiological processes involving large scale microtubule reorganization, such as embryonic development, wound healing, and tumor cell metastasis. Although alterations in microtubules affect numerous cellular responses, no data have yet implicated microtubule dynamics in HIF-1alpha regulation. To investigate the effect of microtubule change upon HIF-1alpha regulation, we treated cells with the microtubule-depolymerizing agents (MDAs) colchicine, vinblastine or nocodazole. We demonstrate that these agents are able to induce transcriptionally active HIF-1. MDA-mediated induction of HIF-1alpha required microtubule depolymerization, since HIF-1alpha levels were unchanged in cells treated with either the microtubule-stabilizing agent paclitaxel, or an inactive form of colchicine, or in colchicine-resistant cells. HIF-1 induction was dependent upon cellular transcription, as transcription inhibitors abrogated HIF-1alpha protein up-regulation. The ability of transcriptional inhibitors to interfere with HIF-1alpha accumulation was specific to the MDA-initiated pathway, as they were ineffective in preventing hypoxia-mediated HIF-1 induction, which occurs by a distinct post-translational pathway. Moreover, we provide evidence implicating a requirement for NFkappaB transcription in the HIF-1 induction mediated by MDAs. The ability of MDAs to induce HIF-1alpha is dependent upon activation of NFkappaB, since inhibition of NFkappaB either pharmacologically or by transfection of an NFkappaB super-repressor plasmid abrogated this induction. Collectively, these data support a model in which NFkappaB is a focal point for the convergence of MDA-mediated signaling events leading to HIF-1 induction, thus revealing a novel aspect of HIF-1alpha regulation and function.
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Affiliation(s)
- Yun-Jin Jung
- Cell and Cancer Biology Branch, Center for Cancer Research, NCI, National Institutes of Health, Rockville, Maryland 20850, USA
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31
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Stebbings H. Cytoskeleton-dependent transport and localization of mRNA. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 211:1-31. [PMID: 11597002 DOI: 10.1016/s0074-7696(01)11016-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Messenger RNAs are localized in both somatic and germ cells as a means of focusing the translation of proteins at specific cellular sites. The signals for this lie within the mRNA, and these are recognized by proteins in the cell. The latter appear to be attached via linker proteins to the transport machinery for localization. In some instances it is a myosin motor which translocates along actin microfilaments, and in others kinesin or dynein motors appear to be responsible for driving the movement of mRNA along microtubule substrates. The way that cytoskeleton-based mRNA translocation is regulated is speculated upon.
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Affiliation(s)
- H Stebbings
- School of Biological Sciences, Washington Singer Laboratories, University of Exeter, United Kingdom
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32
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Forer A, Wilson PJ. Evidence that kinetochore fibre microtubules shorten predominantly at the pole in anaphase flea-beetle spermatocytes. Chromosome Res 2000; 8:151-63. [PMID: 10780704 DOI: 10.1023/a:1009298620707] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Kinetochore spindle fibres in flea-beetle metaphase primary spermatocytes have two regions with distinct morphologies. As seen after staining with antibodies against tubulin, the kinetochore microtubules are tightly bundled in the 5 microm closest to the kinetochore but they splay out in the region closest to the pole. This morphology persists throughout anaphase. This distinct morphology allows one to deduce the site where kinetochore microtubules depolymerise during anaphase. During poleward movement of the autosomes in anaphase, the bundled region shortens by about 0.25 microm for each 1 microm the chromosome moves poleward; this suggests that, during anaphase, 75% of the kinetochore microtubule shortening occurs at the pole end. Sex chromosomes in metaphase cells are separated from the autosomes and do not move poleward at the same time as the autosomes: they are reported to move poleward when the autosomes are in metaphase, to stop part way to the poles, and to move poleward again as the autosomes do (Virkki 1970). Kinetochore microtubules of the sex chromosomes also have bundled and splayed regions; measurements of those regions suggest that these chromosomes may move poleward before the autosomes enter anaphase, but not afterwards.
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Affiliation(s)
- A Forer
- Biology Department, York University, North York, Ontario, Canada.
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Moore RC, Zhang M, Cassimeris L, Cyr RJ. In vitro assembled plant microtubules exhibit a high state of dynamic instability. CELL MOTILITY AND THE CYTOSKELETON 2000; 38:278-86. [PMID: 9384218 DOI: 10.1002/(sici)1097-0169(1997)38:3<278::aid-cm6>3.0.co;2-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Higher plants possess four distinct microtubule arrays. One of these, the cortical array, is involved in orienting the deposition of cellulose microfibrils. This plant interphase array is also notable because it contains exceptionally dynamic microtubules. Although the primary sequence of plant and animal tubulin is similar (79-87% amino acid identity overall) there are some regions of divergence. Thus, one possible explanation for the high state of polymer assembly and turnover that is observed in plant interphase arrays is that the tubulins have evolved differently and possess a higher intrinsic dynamic character than their animal counterparts. This hypothesis was tested using highly purified plant tubulin assembled in vitro. Using high-resolution DIC video-enhanced microscopy, we quantified the four characteristic parameters of dynamic instability of plant microtubules and compared them with animal microtubules. The elongation velocities between plant and animal microtubules are similar, but plant microtubules undergo catastrophes more frequently, do not exhibit any rescues, and have an average shortening velocity of 195 microm/min (compared with 21 microm/min for animal microtubules). These data support the hypothesis that plant tubulin forms microtubules that are intrinsically more dynamic than those of animals.
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Affiliation(s)
- R C Moore
- Department of Biology and Intercollege Program in Plant Physiology, Penn State University, University Park, Pennsylvania 16802, USA
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Spurck T, Forer A, Pickett-Heaps J. Ultraviolet microbeam irradiations of epithelial and spermatocyte spindles suggest that forces act on the kinetochore fibre and are not generated by its disassembly. CELL MOTILITY AND THE CYTOSKELETON 2000; 36:136-48. [PMID: 9015202 DOI: 10.1002/(sici)1097-0169(1997)36:2<136::aid-cm4>3.0.co;2-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ultraviolet (UV) microbeam irradiations of crane-fly spermatocyte and newt epithelial spindles severed kinetochore fibres (KT-fibres), creating areas of reduced birefringence (ARBs): the remnant KT-fibre consists of two "stubs," a pole-stub attached to the pole and a KT-stub attached to the kinetochore. KT-stubs remained visible but pole-stubs soon became undetectable [Forer et al., 1996]. At metaphase, in both cell types the KT-stub often changed orientation immediately after irradiation and its tip steadily moved poleward. In spermatocytes, the chromosome attached to the KT-stub remained at the equator as the KT-stub elongated. In epithelial cells, the KT-stub sometimes elongated as the associated chromosome remained at the equator; other times the associated chromosome moved poleward together with the KT-stub, albeit only a short distance toward the pole. When an ARB was generated at anaphase, chromosome(s) with a KT-stub often continued to move poleward. In spermatocytes, this movement was accompanied by steady elongation of the KT-stub. In epithelial cells, chromosomes accelerated polewards after irradiation until the KT-stubs reached the pole, after which chromosome movement returned to normal speeds. In some epithelial cells fine birefringent fibres by chance were present along one edge of ARBs; these remnant fibres buckled and broke as the KT-stub and chromosome moved polewards. Similarly, KT-stubs that moved into pole stubs (or astral fibres) caused the pole stubs (or astral fibres) to bend sharply from the point of impact. Our results contradict models of chromosome movement that postulate that force is generated by the kinetochore disassembling the KT-fibre. Instead, these results suggest that poleward directed forces act on the KT-fibre and the KT-stub and suggest that continuity of microtubules between kinetochore and pole is not obligatory for achieving anaphase motion to the pole.
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Affiliation(s)
- T Spurck
- School of Botany, University of Melbourne, Parkville, Vic., Australia
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Moore RC, Durso NA, Cyr RJ. Elongation factor-1alpha stabilizes microtubules in a calcium/calmodulin-dependent manner. CELL MOTILITY AND THE CYTOSKELETON 2000; 41:168-80. [PMID: 9786091 DOI: 10.1002/(sici)1097-0169(1998)41:2<168::aid-cm7>3.0.co;2-a] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Elongation factor-1alpha (EF-1alpha), a highly conserved protein named for its role in protein translation, is also a microtubule-associated protein (MAP). We used high-resolution differential interference contrast microscopy to quantify the effect of substoichiometric amounts of EF-1alpha (isolated from Daucus carota) on the dynamic instability of microtubules assembled in vitro from either animal or plant tubulin. EF-1alpha modulates the dynamic behavior of microtubules assembled from either tubulin source, resulting in longer and more persistent microtubules. EF-1alpha, at a 1:20 molar ratio to tubulin, significantly (P < 0.05) reduces the frequency of catastrophe threefold and decreases shortening velocities almost twofold for microtubules assembled from animal tubulin. For microtubules assembled from plant tubulin, substoichiometric amounts of EF-1alpha significantly (P < 0.05) suppress the frequency of catastrophe greater than twofold and causes an almost threefold reduction in shortening velocities. Elongation velocities increase almost twofold and rescues, which are not observed in the absence of EF-1alpha, occur. In addition, calcium/calmodulin (Ca2+/CaM), which regulates the ability of EF-1alpha to bundle taxol-stabilized microtubules in vitro, also modulates the effect of EF-1alpha on the dynamic behavior of microtubules assembled in vitro from animal tubulin. Microtubule severing in the presence of EF-1alpha was never observed. These data support the hypothesis that EF-1alpha modulates the dynamic behavior of microtubules assembled in vitro in a Ca2+/CaM-dependent manner.
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Affiliation(s)
- R C Moore
- Department of Biology, Penn State University, University Park 16802, USA
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36
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Wilson PJ, Forer A. Effects of nanomolar taxol on crane-fly spermatocyte spindles indicate that acetylation of kinetochore microtubules can be used as a marker of poleward tubulin flux. CELL MOTILITY AND THE CYTOSKELETON 2000; 37:20-32. [PMID: 9142436 DOI: 10.1002/(sici)1097-0169(1997)37:1<20::aid-cm3>3.0.co;2-l] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Kinetochore microtubules (kMTs) in meiosis-I crane-fly spermatocytes label strongly with antibodies to acetylated alpha-tubulin, except near the kinetochore, where there is a "gap" in labelling [Wilson and Forer, 1989: Cell Motil. Cytoskeleton 14:237-250]. Previously we measured the length of gaps in metaphase and anaphase cells, and from these data deduced that during anaphase kMTs disassemble primarily at the pole [Wilson et al., 1994: J. Cell Sci. 107:3015-3027]. However, the study rested on our assumption that the gap is due to a time lag between polymerisation at the kinetochore and acetylation of the polymerised MTs: the subunits enter kMTs at the kinetochore and do not become acetylated until they have moved poleward. In the present study we tested our interpretation of the gap by treating spermatocytes with paclitaxel (taxol) to reduce microtubule dynamics [e.g. Jordan et al., 1993: Proc. Natl. Acad. Sci. U.S.A. 90:9552-9556]. We expected that if our assumptions were correct, taxol would slow tubulin addition at the kinetochore but acetylation would continue, and the gap in acetylation would get smaller. We found that 5 to 50 nM taxol results in increased acetylation of kMTs at the kinetochore, supporting our interpretation of the gap. Nanomolar taxol also increases the level of acetylation in other microtubule populations and causes changes in spindle morphology.
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Affiliation(s)
- P J Wilson
- Biology Department, York University, North York, Ontario, Canada
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38
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Abstract
The polymerization dynamics of microtubules are central to their biological functions. Polymerization dynamics allow microtubules to adopt spatial arrangements that can change rapidly in response to cellular needs and, in some cases, to perform mechanical work. Microtubules utilize the energy of GTP hydrolysis to fuel a unique polymerization mechanism termed dynamic instability. In this review, we first describe progress toward understanding the mechanism of dynamic instability of pure tubulin and then discuss the function and regulation of microtubule dynamic instability in living cells.
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Affiliation(s)
- A Desai
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143, USA.
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39
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Gordon SR, Buxar RM. Inhibition of cytoskeletal reorganization stimulates actin and tubulin syntheses during injury-induced cell migration in the corneal endothelium. J Cell Biochem 1997. [DOI: 10.1002/(sici)1097-4644(19971201)67:3<409::aid-jcb12>3.0.co;2-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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40
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Pérez M, Aloria K, Zabala JC, Avila J. A putative beta-tubulin phosphate-binding motif is involved in lateral microtubule protofilament interactions. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 248:840-7. [PMID: 9342237 DOI: 10.1111/j.1432-1033.1997.t01-1-00840.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have investigated the role of a putative GTP-binding beta-tubulin motif in microtubule polymerization. A peptide containing residues 126-142 of the beta-tubulin subunit (peptide G) was synthesised and an antibody against it raised. Peptide G prevents the binding of GTP to tubulin and also microtubule polymerization but not the formation of vinblastine-induced tubulin spirals, suggesting that it may prevent lateral but not longitudinal tubulin-tubulin interactions. The antibody to peptide G shows little reaction with the interphase microtubule network, mitotic spindles or midbody of cultured cells, whereas it clearly reacts with vinblastine-induced paracrystals. These results suggest that this putative phosphate-binding site present in beta-tubulin could be involved in the lateral tubulin-tubulin interactions along the microtubule structure.
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Affiliation(s)
- M Pérez
- Centro de Biología Molecular (CSIC-UAM) Facultad de Ciencias, Universidad Autónoma de Madrid, Spain
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41
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Barton NR, Goldstein LS. Going mobile: microtubule motors and chromosome segregation. Proc Natl Acad Sci U S A 1996; 93:1735-42. [PMID: 8700828 PMCID: PMC39850 DOI: 10.1073/pnas.93.5.1735] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Proper chromosome segregation in eukaryotes depends upon the mitotic and meiotic spindles, which assemble at the time of cell division and then disassemble upon its completion. These spindles are composed in large part of microtubules, which either generate force by controlled polymerization and depolymerization or transduce force generated by molecular microtubule motors. In this review, we discuss recent insights into chromosome segregation mechanisms gained from the analyses of force generation during meiosis and mitosis. These analyses have demonstrated that members of the kinesin superfamily and the dynein family are essential in all organisms for proper chromosome and spindle behavior. It is also apparent that forces generated by microtubule polymerization and depolymerization are capable of generating forces sufficient for chromosome movement in vitro; whether they do so in vivo is as yet unclear. An important realization that has emerged is that some spindle activities can be accomplished by more than one motor so that functional redundancy is evident. In addition, some meiotic or mitotic movements apparently occur through the cooperative action of independent semiredundant processes. Finally, the molecular characterization of kinesin-related proteins has revealed that variations both in primary sequence and in associations with other proteins can produce motor complexes that may use a variety of mechanisms to transduce force in association with microtubules. Much remains to be learned about the regulation of these activities and the coordination of opposing and cooperative events involved in chromosome segregation; this set of problems represents one of the most important future frontiers of research.
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Affiliation(s)
- N R Barton
- Howard Hughes Medical Institute, Department of Pharmacology, University of California San Diego, La Jolla 92093-0683, USA
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42
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Gard DL, Cha BJ, Schroeder MM. Confocal immunofluorescence microscopy of microtubules, microtubule-associated proteins, and microtubule-organizing centers during amphibian oogenesis and early development. Curr Top Dev Biol 1996; 31:383-431. [PMID: 8746671 DOI: 10.1016/s0070-2153(08)60234-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- D L Gard
- Department of Biology, University of Utah, Salt Lake City 84112, USA
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43
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Abstract
Most mammalian microtubules disassemble at low temperature, but some are cold stable. This probably has little to do with a need for cold-stable microtubules, but reflects that certain populations of microtubules must be stabilized for specific functions. There are several routes by which to achieve cold stability. Factors that interact with microtubules, such as microtubule-associated proteins, STOPs (stable tubule only polypeptides), histones, and possibly capping factors, are involved. Specific tubulin isotypes and posttranslational modifications might also be of importance. More permanent stable microtubules can be achieved by bundling factors, associations to membranes, as well as by assembly of microtubule doublets and triplets. This is, however, not the explanation for cold adaptation of microtubules from poikilothermic animals, that is, animals that must have all their microtubules adapted to low temperatures. All evidence so far suggests that cold adaptation is intrinsic to the tubulins, but it is unknown whether it depends on different amino acid sequences or posttranslational modifications.
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Affiliation(s)
- M Wallin
- Department of Zoophysiology, University of Göteborg, Sweden
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44
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Wilson PJ, Forer A, Leggiadro C. Evidence that kinetochore microtubules in crane-fly spermatocytes disassemble during anaphase primarily at the poleward end. J Cell Sci 1994; 107 ( Pt 11):3015-27. [PMID: 7699001 DOI: 10.1242/jcs.107.11.3015] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Anaphase chromosome motion involves the disassembly of kinetochore microtubules. We wished to determine the site of kinetochore microtubule disassembly during anaphase in crane-fly spermatocytes. In crane-fly spermatocyte spindles, monoclonal antibody 6–11B-1 to acetylated alpha-tubulin labels kinetochore microtubules almost exclusively, with an area immediately adjacent to the kinetochore being weakly or not labelled. This ‘gap’ in acetylation at the kinetochore serves as a natural marker of kinetochore microtubules in the kinetochore fibre. We measured the length of the gap on kinetochore fibres in metaphase and anaphase in order to deduce the fate of the gap during anaphase; we used this information to determine where kinetochore microtubules disassemble in anaphase. Gap lengths were measured from confocal microscope images of fixed spermatocytes dual labelled with 6–11B-1 to acetylated alpha-tubulin and YL1/2 to tyrosinated alpha-tubulin, the latter being used to determine the positions of kinetochores. In metaphase the average gap length was 1.7 microns. In anaphase, the gap appeared to decrease in length abruptly by about 0.4 microns, after which it decreased in length by about 0.2 microns for every 1 microns that the chromosome moved poleward. PacMan models of chromosome movement predict that this ‘gap’ in staining should disappear in anaphase at a rate equal to that of chromosome movement. Thus, our results do not support theories of chromosome motion that require disassembly solely at the kinetochore; rather, in crane-fly spermatocytes kinetochore microtubule disassembly in anaphase seems to take place primarily at the poles.
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Affiliation(s)
- P J Wilson
- Biology Department, York University, North York, Ontario, Canada
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45
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47
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Cassimeris L, Rieder CL, Salmon ED. Microtubule assembly and kinetochore directional instability in vertebrate monopolar spindles: implications for the mechanism of chromosome congression. J Cell Sci 1994; 107 ( Pt 1):285-97. [PMID: 8175915 DOI: 10.1242/jcs.107.1.285] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have proposed previously a kinetochore motor-polar ejection model for chromosome congression to the metaphase plate where forces generated at the kinetochore are antagonized by away-from-the pole forces generated within each half-spindle on the chromosome arms. This model was based in large part on observations of the behavior of chromosomes on monopolar spindles. In these cells chromosomes typically become attached to the pole by only one kinetochore fiber. These mono-oriented chromosomes move to positions away from the pole even though they are pulled poleward at their kinetochores. Their arms are also ejected away from the pole when severed from the centromere. Here we have characterized further the properties of monopolar spindles in newt lung epithelial cells to determine the similarities between monopolar and bipolar spindles. We found no significant differences between monopolar and bipolar spindles over the parameters examined, which included: microtubule dynamics as measured by fluorescence redistribution after photobleaching; the ability of polar microtubule arrays to push chromosome arms away from the pole; the dependence of chromosome position relative to the pole on microtubule assembly; the number of kinetochore microtubules per kinetochore; and the directional instability of kinetochore motion during chromosome oscillations poleward and away-from-the-pole. As in bipolar spindles, kinetochore directional instability is characterized by abrupt switching between constant velocity phases of poleward and away-from-the-pole motion. From these data we conclude that the mechanism(s) responsible for chromosome positioning in monopolar spindles are fundamentally the same as those in bipolar spindles; only the geometry of the two spindle forms and the interplay between sister kinetochore directional instabilities are different. We also found no correlation in the kinetochore-to-pole distance with kinetochore microtubule number in monopolar spindles, but a strong qualitative correlation with microtubule density. This finding indicates that oscillations of mono-oriented chromosomes in both monopolar and bipolar spindles occur because chromosomes persist in poleward motion until they reach a density of polar microtubules sufficiently high to promote switching to away-from-the-pole motion. As the kinetochore and chromosome arms move away-from-the-pole, microtubule density decreases and the kinetochore switches to poleward motion, pulling the chromosome arms back into regions of higher microtubule density. The mechanism regulating kinetochore switching between poleward and away-from-the-pole motion is poorly understood, but may depend on tension at the kinetochore generated by pushing forces on the chromosome arms produced by the polar microtubule arrays.
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Affiliation(s)
- L Cassimeris
- Department of Molecular Biology, Lehigh University, Bethlehem, PA 18015
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48
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Martin SR, Schilstra MJ, Bayley PM. Dynamic instability of microtubules: Monte Carlo simulation and application to different types of microtubule lattice. Biophys J 1993; 65:578-96. [PMID: 8218889 PMCID: PMC1225761 DOI: 10.1016/s0006-3495(93)81091-9] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Dynamic instability is the term used to describe the transition of an individual microtubule, apparently at random, between extended periods of slow growth and brief periods of rapid shortening. The typical sawtooth growth and shortening transition behavior has been successfully simulated numerically for the 13-protofilament microtubule A-lattice by a lateral cap model (Bayley, P. M., M. J. Schilstra, and S. R. Martin. 1990. J. Cell Sci. 95:33-48). This kinetic model is now extended systematically to other related lattice geometries, namely the 13-protofilament B-lattice and the 14-protofilament A-lattice, which contain structural "seams". The treatment requires the assignment of the free energies of specific protein-protein interactions in terms of the basic microtubule lattice. It is seen that dynamic instability is not restricted to the helically symmetric 13-protofilament A-lattice but is potentially a feature of all A- and B-lattices, irrespective of protofilament number. The advantages of this general energetic approach are that it allows a consistent treatment to be made for both ends of any microtubule lattice. Important features are the predominance of longitudinal interactions between tubulin molecules within the same protofilament and the implication of a relatively favorable interaction of tubulin-GDP with the growing microtubule end. For the three lattices specifically considered, the treatment predicts the dependence of the transition behavior upon tubulin concentration as a cooperative process, in good agreement with recent experimental observations. The model rationalizes the dynamic properties in terms of a metastable microtubule lattice of tubulin-GDP, stabilized by the kinetic process of tubulin-GTP addition. It provides a quantitative basis for the consideration of in vitro microtubule behaviour under both steady-state and non-steady-state conditions, for comparison with experimental data on the dilution-induced disassembly of microtubules. Similarly, the effects of small tubulin-binding molecules such as GDP and nonhydrolyzable GTP analogues are readily treated. An extension of the model allows a detailed quantitative examination of possible modes of substoichiometric action of a number of antimitotic drugs relevant to cancer chemotherapy.
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Affiliation(s)
- S R Martin
- Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London, England
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49
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Liu B, Marc J, Joshi HC, Palevitz BA. A gamma-tubulin-related protein associated with the microtubule arrays of higher plants in a cell cycle-dependent manner. J Cell Sci 1993; 104 ( Pt 4):1217-28. [PMID: 7686171 DOI: 10.1242/jcs.104.4.1217] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An antibody specific for a conserved gamma-tubulin peptide identifies a plant polypeptide of 58 kDa. gamma-Tubulin antibody affinity purified from this polypeptide recognizes the centrosome in mammalian cells. Using immunofluorescence microscopy, we determined the distribution of this gamma-tubulin-related polypeptide during the complex changes in microtubule arrays that occur throughout the plant cell cycle. We report a punctate association of gamma-tubulin-related polypeptide with the cortical microtubule array and the preprophase band. As cells enter prophase, gamma-tubulin-related polypeptide accumulates around the nucleus and forms a polar cap from which early spindle microtubules radiate. During metaphase and anaphase, gamma-tubulin-related polypeptide preferentially associates with kinetochore fibers and eventually accumulates at the poles. In telophase, localization occurs over the phragmoplast. gamma-Tubulin-related polypeptide appears to be excluded from the plus ends of microtubules at the metaphase plate and cell plate. Its distribution during the cell cycle may be significant in light of differences in the behavior and organization of plant microtubules. The identification of gamma-tubulin-related polypeptide could help characterize microtubule organizing centers in these organisms.
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Affiliation(s)
- B Liu
- Department of Botany, University of Georgia, Athens 30602
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50
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Pryer NK, Walker RA, Skeen VP, Bourns BD, Soboeiro MF, Salmon ED. Brain microtubule-associated proteins modulate microtubule dynamic instability in vitro. Real-time observations using video microscopy. J Cell Sci 1992; 103 ( Pt 4):965-76. [PMID: 1487507 DOI: 10.1242/jcs.103.4.965] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used video assays to study the dynamic instability behavior of individual microtubules assembled in vitro with purified tau, purified MAP2 or a preparation of unfractionated heat-stable MAPs. Axoneme-nucleated microtubules were assembled from pure tubulin at concentrations between 4 and 9 microM in the presence of MAPs, and observed by video-differential interference contrast microscopy. Microtubules co-assembled with each MAP preparation exhibited the elongation and rapid shortening phases and the abrupt transitions (catastrophe and rescue) characteristic of dynamic instability. Each MAP preparation increased the microtubule elongation rate above that for purified tubulin alone by decreasing the tubulin subunit dissociation rate during elongation. The brain MAPs used in this study reduced the rate of microtubule rapid shortening, but allowed significant loss of polymer during the shortening phase. Purified tau and MAP2 decreased the frequency of catastrophe and increased the frequency of rescue, while the heat-stable MAPs suppressed catastrophe at all but the lowest tubulin concentrations. Thus, each of these MAPs modulates, but does not abolish, dynamic instability behavior of microtubules. We propose a model to explain how MAP2 and tau bind to the microtubule lattice at sites along protofilaments so that the MAPs promote polymerization, but do not significantly block the mechanism of rapid shortening inherent in the tubulin lattice. Rapid shortening, when it occurs, proceeds primarily by the dissociation of short fragments of protofilaments, which contain the bound MAPs.
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Affiliation(s)
- N K Pryer
- Department of Biology, University of North Carolina, Chapel Hill 27599
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