151
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Mouse norovirus 1 utilizes the cytoskeleton network to establish localization of the replication complex proximal to the microtubule organizing center. J Virol 2012; 86:4110-22. [PMID: 22301146 DOI: 10.1128/jvi.05784-11] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human noroviruses (family Caliciviridae) are the leading cause of nonbacterial gastroenteritis worldwide. Although Human noroviruses are significant enteric pathogens, there exists no reliable vaccine or therapy to treat infected individuals. To date, attempts to cultivate Human noroviruses within the laboratory have met with little success; however, the related murine norovirus mouse norovirus 1 (MNV-1) has provided an ideal model system to study norovirus replication due to the ease with which the virus is cultivated and the ability to infect a small animal model with this virus. Previously we have identified the association between MNV-1 and components of the host secretory pathway and proposed a role for the viral open reading frame 1 proteins in the replication cycle. Here we describe for the first time a role for cytoskeletal components in early MNV-1 replication events. We show that the MNV-1 utilizes microtubules to position the replication complex adjacent to the microtubule organizing center. Chemical disruption of the microtubule network disperses the sites of MNV-1 replication throughout the cell and impairs production of viral protein and infectious virus. Furthermore, we demonstrate the ability of MNV-1 to redistribute acetylated tubulin to the replication complex and that this association is potentially mediated via the MNV-1 major structural protein, VP1. Transient expression of MNV-1 VP1 exhibited extensive colocalization with both α-tubulin and acetylated tubulin and was observed to alter the distribution of acetylated tubulin in transfected cells. This study highlights the role of the cytoskeleton in early virus replication events and demonstrates the importance of this interaction in establishing the intracellular location of MNV-1 replication complexes.
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152
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Margolin G, Gregoretti IV, Cickovski TM, Li C, Shi W, Alber MS, Goodson HV. The mechanisms of microtubule catastrophe and rescue: implications from analysis of a dimer-scale computational model. Mol Biol Cell 2011; 23:642-56. [PMID: 22190741 PMCID: PMC3279392 DOI: 10.1091/mbc.e11-08-0688] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
ETOC: The behavior of a dimer-scale computational model predicts that short interprotofilament “cracks” (laterally unbonded regions between protofilaments) exist even at the tips of growing MTs and that rapid fluctuations in the depths of these cracks govern both catastrophe and rescue. Microtubule (MT) dynamic instability is fundamental to many cell functions, but its mechanism remains poorly understood, in part because it is difficult to gain information about the dimer-scale events at the MT tip. To address this issue, we used a dimer-scale computational model of MT assembly that is consistent with tubulin structure and biochemistry, displays dynamic instability, and covers experimentally relevant spans of time. It allows us to correlate macroscopic behaviors (dynamic instability parameters) with microscopic structures (tip conformations) and examine protofilament structure as the tip spontaneously progresses through both catastrophe and rescue. The model's behavior suggests that several commonly held assumptions about MT dynamics should be reconsidered. Moreover, it predicts that short, interprotofilament “cracks” (laterally unbonded regions between protofilaments) exist even at the tips of growing MTs and that rapid fluctuations in the depths of these cracks influence both catastrophe and rescue. We conclude that experimentally observed microtubule behavior can best be explained by a “stochastic cap” model in which tubulin subunits hydrolyze GTP according to a first-order reaction after they are incorporated into the lattice; catastrophe and rescue result from stochastic fluctuations in the size, shape, and extent of lateral bonding of the cap.
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Affiliation(s)
- Gennady Margolin
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, IN 46556, USA
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153
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Nabavi N, Khandani A, Camirand A, Harrison RE. Effects of microgravity on osteoclast bone resorption and osteoblast cytoskeletal organization and adhesion. Bone 2011; 49:965-74. [PMID: 21839189 DOI: 10.1016/j.bone.2011.07.036] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 07/19/2011] [Accepted: 07/23/2011] [Indexed: 01/09/2023]
Abstract
Exposure to microgravity has been associated with several physiological changes in astronauts, including an osteoporosis-like loss in bone mass. Despite many in vivo and in vitro studies in both microgravity and simulated microgravity conditions, the mechanism for bone loss is still not clear. The lack of weight-bearing forces makes microgravity an ideal physical stimulus to assess bone cell responses. In this work, we conduct a unique investigation of the effects of microgravity on bone-producing osteoblasts and, in parallel, on bone-resorbing osteoclasts. An increase in total number of discrete resorption pits is observed in osteoclasts that experienced microgravity versus ground controls. We further show that osteoblasts exposed to 5 days of microgravity have shorter and wavier microtubules (MTs), smaller and fewer focal adhesions, and thinner cortical actin and stress fibers. Space-flown osteoblasts present extended cell shapes as well as significantly more disrupted and often fragmented or condensed nuclei. The absence of gravitational forces therefore causes both an increase in bone resorption by osteoclasts, and a decrease in osteoblast cellular integrity. The observed effects on both major bone cell types likely accelerate bone loss in microgravity environments, and additionally offer a potential explanation to the development of disuse osteoporosis on Earth.
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Affiliation(s)
- Noushin Nabavi
- Department of Cell and Systems Biology, University of Toronto Scarborough, Toronto, Ontario, Canada
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154
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Alisaraie L, Tuszynski JA. Determination of Noscapine’s Localization and Interaction with the Tubulin-α/β Heterodimer. Chem Biol Drug Des 2011; 78:535-46. [DOI: 10.1111/j.1747-0285.2011.01189.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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155
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Wang S, Kurepa J, Hashimoto T, Smalle JA. Salt stress-induced disassembly of Arabidopsis cortical microtubule arrays involves 26S proteasome-dependent degradation of SPIRAL1. THE PLANT CELL 2011; 23:3412-27. [PMID: 21954463 PMCID: PMC3203425 DOI: 10.1105/tpc.111.089920] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 08/30/2011] [Accepted: 09/12/2011] [Indexed: 05/18/2023]
Abstract
The dynamic instability of cortical microtubules (MTs) (i.e., their ability to rapidly alternate between phases of growth and shrinkage) plays an essential role in plant growth and development. In addition, recent studies have revealed a pivotal role for dynamic instability in the response to salt stress conditions. The salt stress response includes a rapid depolymerization of MTs followed by the formation of a new MT network that is believed to be better suited for surviving high salinity. Although this initial depolymerization response is essential for the adaptation to salt stress, the underlying molecular mechanism has remained largely unknown. Here, we show that the MT-associated protein SPIRAL1 (SPR1) plays a key role in salt stress-induced MT disassembly. SPR1, a microtubule stabilizing protein, is degraded by the 26S proteasome, and its degradation rate is accelerated in response to high salinity. We show that accelerated SPR1 degradation is required for a fast MT disassembly response to salt stress and for salt stress tolerance.
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Affiliation(s)
- Songhu Wang
- Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546
| | - Jasmina Kurepa
- Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546
| | - Takashi Hashimoto
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
| | - Jan A. Smalle
- Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546
- Address correspondence to
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156
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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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157
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Smoter M, Bodnar L, Duchnowska R, Stec R, Grala B, Szczylik C. The role of Tau protein in resistance to paclitaxel. Cancer Chemother Pharmacol 2011; 68:553-7. [PMID: 21713447 PMCID: PMC3162141 DOI: 10.1007/s00280-011-1696-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Accepted: 06/15/2011] [Indexed: 12/05/2022]
Abstract
Resistance to taxanes, related to limited efficacy of systemic therapy in cancer patients, is multifactorial. Among mechanisms of resistance to taxanes, those related to microtubule-associated proteins (MAP), including protein Tau, are of great importance. Protein Tau (50–64 kD) binds to beta-tubulin in the same place as paclitaxel. In preclinical studies, low expression of Tau in cancer cells was associated with increased sensitivity to paclitaxel. High expression of Tau protein in ER-positive breast cancers indicates resistance to taxane-containing chemotherapy and sensitivity to hormonal treatment. This article reviews current knowledge on predictive value of protein Tau in response to taxanes. Better understanding of its role may facilitate patients selection to this sort of treatment and lead to treatment optimization.
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Affiliation(s)
- Marta Smoter
- Klinika Onkologii Kobiet, Wojskowy Instytut Medyczny, Ul. Szaserów 128, Warszawa, Poland.
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158
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Thiele A, Krentzlin K, Erdmann F, Rauh D, Hause G, Zerweck J, Kilka S, Pösel S, Fischer G, Schutkowski M, Weiwad M. Parvulin 17 promotes microtubule assembly by its peptidyl-prolyl cis/trans isomerase activity. J Mol Biol 2011; 411:896-909. [PMID: 21756916 DOI: 10.1016/j.jmb.2011.06.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 06/22/2011] [Accepted: 06/22/2011] [Indexed: 11/28/2022]
Abstract
The parvulin-type peptidyl-prolyl cis/trans isomerases (PPIases) have been shown to be involved in tumor progression and the pathogenesis of Alzheimer's disease and were therefore a subject of intense research. Here, we describe a role for parvulin 17 in microtubule assembly. Co-precipitation experiments and sedimentation assays demonstrated that parvulin 17 interacts with tubulin in a GTP-dependent manner and thereby promotes the formation of microtubules, as shown by transmission electron microscopy and a microtubule polymerization assay. The microtubule-assembly-promoting properties of parvulin 17 seem to depend on its PPIase activity. Thus, catalytic deficient variants of parvulin 17 were not able to promote microtubule formation. Accordingly, inhibitors of parvulin 17 activity also prevent parvulin-catalyzed tubulin polymerization. The analysis of tubulin interaction sites on parvulin using peptide microarrays revealed that tubulin interacts with the substrate binding pocket of parvulin. Additionally, β-tubulin peptide scan on microarrays demonstrates interaction of parvulin 17 with an Arg-Pro-Asp motif corresponding to proline residue 87 of β-tubulin. Confocal laser scanning microscopy points to a function of parvulin 17 in microtubule dynamics as well. Parvulin 17 is predominantly found in the cytosol and colocalizes with microtubules.
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Affiliation(s)
- Alexandra Thiele
- Max Planck Research Unit for Enzymology of Protein Folding, Weinbergweg 22, D-06120 Halle/Saale, Germany
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159
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Wang S, Kurepa J, Smalle JA. Ultra-small TiO(2) nanoparticles disrupt microtubular networks in Arabidopsis thaliana. PLANT, CELL & ENVIRONMENT 2011; 34:811-20. [PMID: 21276012 DOI: 10.1111/j.1365-3040.2011.02284.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In spite of the mounting concerns, current understanding of the extent and mechanisms of phytotoxicity of manufactured nanomaterials remains limited. Here we show that in Arabidopsis thaliana, ultra-small anatase TiO(2) nanoparticles cause reorganization and elimination of microtubules followed by the accelerated and 26S proteasome-dependent degradation of tubulin monomers. Similar to other microtubule-disrupting agents, TiO(2) nanoparticles induce isotropic growth of root cells. Because microtubules are essential for the normal function of all eukaryotic cells, these results reveal a potentially important consequence of environmental pollution by this widely used nanomaterial.
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Affiliation(s)
- Songhu Wang
- Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546, USA
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160
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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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161
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Tischfield MA, Cederquist GY, Gupta ML, Engle EC. Phenotypic spectrum of the tubulin-related disorders and functional implications of disease-causing mutations. Curr Opin Genet Dev 2011; 21:286-94. [PMID: 21292473 DOI: 10.1016/j.gde.2011.01.003] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 12/23/2010] [Accepted: 01/03/2011] [Indexed: 12/17/2022]
Abstract
A spectrum of neurological disorders characterized by abnormal neuronal migration, differentiation, and axon guidance and maintenance have recently been attributed to missense and splice-site mutations in the genes that encode α-tubulin and β-tubulin isotypes TUBA1A, TUBA8, TUBB2B, and TUBB3, all of which putatively coassemble into neuronal microtubules. The resulting nervous system malformations can include different types of cortical malformations, defects in commissural fiber tracts, and degeneration of motor and sensory axons. Many clinical phenotypes and brain malformations are shared among the various mutations regardless of structural location and/or isotype, while others segregate with distinct amino acids or functional domains within tubulin. Collectively, these disorders provide novel paradigms for understanding the biological functions of microtubules and their core components in normal health and disease.
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Affiliation(s)
- Max A Tischfield
- Department of Molecular Biology and Genetics, Johns Hopkins Medical School, 725 North Wolfe St., PCTB 804, Baltimore, MD 21205, United States
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162
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Lee NPY, Cheng CY. Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2011; 1:25-32. [PMID: 19794905 PMCID: PMC2715196 DOI: 10.4161/oxim.1.1.6856] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.
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Affiliation(s)
- Nikki P Y Lee
- Department of Medicine/Surgery, University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
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163
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Cheishvili D, Maayan C, Cohen-Kupiec R, Lefler S, Weil M, Ast G, Razin A. IKAP/Elp1 involvement in cytoskeleton regulation and implication for familial dysautonomia. Hum Mol Genet 2011; 20:1585-94. [PMID: 21273291 DOI: 10.1093/hmg/ddr036] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Deficiency in the IKAP/Elp1 protein leads to the recessive sensory autosomal congenital neuropathy which is called familial dysautonomia (FD). This protein was originally identified as a role player in transcriptional elongation being a subunit of the RNAPII transcriptional Elongator multi-protein complex. Subsequently, IKAP/Elp1 was shown to play various functions in the cytoplasm. Here, we describe experiments performed with IKAP/Elp1 downregulated cell lines and FD-derived cells and tissues. Immunostaining of the cytoskeleton component α-tubulin in IKAP/Elp1 downregulated cells revealed disorganization of the microtubules (MTs) that was reflected in aberrant cell shape and process formation. In contrast to a recent report on the decrease in α-tubulin acetylation in IKAP/Elp1 downregulated cells, we were unable to observe any effect of IKAP/Elp1 deficiency on α-tubulin acetylation in the FD cerebrum and in a variety of IKAP/Elp1 downregulated cell lines. To explore possible candidates involved in the observed aberrations in MTs, we focused on superior cervical ganglion-10 protein (SCG10), also called STMN2, which is known to be an MT destabilizing protein. We have found that SCG10 is upregulated in the IKAP/Elp1-deficient FD cerebrum, FD fibroblasts and in IKAP/Elp1 downregulated neuroblastoma cell line. To better understand the effect of IKAP/Elp1 deficiency on SCG10 expression, we investigated the possible involvement of RE-1-silencing transcription factor (REST), a known repressor of the SCG10 gene. Indeed, REST was downregulated in the IKAP/Elp1-deficient FD cerebrum and IKAP/Elp1 downregulated neuroblastoma cell line. These results could shed light on a possible link between IKAP/Elp1 deficiency and cytoskeleton destabilization.
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Affiliation(s)
- David Cheishvili
- Department of Developmental Biology and Cancer Research, Institute of Medical Research Israel-Canada, The Hebrew University Hadassah Medical School, Jerusalem, Israel
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164
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Xie R, Nguyen S, McKeehan WL, Liu L. Acetylated microtubules are required for fusion of autophagosomes with lysosomes. BMC Cell Biol 2010; 11:89. [PMID: 21092184 PMCID: PMC2995476 DOI: 10.1186/1471-2121-11-89] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 11/22/2010] [Indexed: 11/28/2022] Open
Abstract
Background Autophagy is a dynamic process during which isolation membranes package substrates to form autophagosomes that are fused with lysosomes to form autolysosomes for degradation. Although it is agreed that the LC3II-associated mature autophagosomes move along microtubular tracks, it is still in dispute if the conversion of LC3I to LC3II before autophagosomes are fully mature and subsequent fusion of mature autophagosomes with lysosomes require microtubules. Results We use biochemical markers of autophagy and a collection of microtubule interfering reagents to test the question. Results show that interruption of microtubules with either microtubule stabilizing paclitaxel or destabilizing nocodazole similarly impairs the conversion of LC3I to LC3II, but does not block the degradation of LC3II-associated autophagosomes. Acetylation of microtubules renders them resistant to nocodazole treatment. Treatment with vinblastine that causes depolymerization of both non-acetylated and acetylated microtubules results in impairment of both LC3I-LC3II conversion and LC3II-associated autophagosome fusion with lysosomes. Conclusions Acetylated microtubules are required for fusion of autophagosomes with lysosomes to form autolysosomes.
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Affiliation(s)
- Rui Xie
- Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030-3303, USA
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165
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Rendine S, Pieraccini S, Sironi M. Vinblastine perturbation of tubulin protofilament structure: a computational insight. Phys Chem Chem Phys 2010; 12:15530-6. [PMID: 20978652 DOI: 10.1039/c0cp00594k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Tubulin is a heterodimeric protein whose self assembly leads to the formation of protofilaments and of more complex structures called microtubules, key components of the cytoskeleton which have a fundamental role in the cell division process. Due to its biological function, tubulin is the target of many antitumoral molecules that exert their action on proliferating tumoral cells. Among these drugs, vinblastine has been widely used in therapy for a long time, albeit its mechanism of interaction with tubulin has remained elusive until recently. Vinblastine acts as a microtubule destabilizing agent and induces the formation of curved or ring-shaped tubulin polymers instead of linear protofilaments in vitro. In this paper we compare, using molecular dynamics simulations and free energy calculations, the network of interactions that allow the assembly of model linear protofilaments with those present in curved tubulin polymers complexed with vinblastine. It is shown that vinblastine, wedging between tubulin heterodimers, actually mediates part of the interactions between them and acts by crosslinking the two proteins, leading to the observed curved polymers rather than to their disassembly.
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Affiliation(s)
- Stefano Rendine
- Dipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano, Via Golgi 19, 20133, Milano, Italy
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166
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Kumar A, Heise H, Blommers MJJ, Krastel P, Schmitt E, Petersen F, Jeganathan S, Mandelkow EM, Carlomagno T, Griesinger C, Baldus M. Interaction of Epothilone B (Patupilone) with Microtubules as Detected by Two-Dimensional Solid-State NMR Spectroscopy. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201001946] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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167
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Kumar A, Heise H, Blommers MJJ, Krastel P, Schmitt E, Petersen F, Jeganathan S, Mandelkow EM, Carlomagno T, Griesinger C, Baldus M. Interaction of Epothilone B (Patupilone) with Microtubules as Detected by Two-Dimensional Solid-State NMR Spectroscopy. Angew Chem Int Ed Engl 2010; 49:7504-7. [DOI: 10.1002/anie.201001946] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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168
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Wang-Gillam A, Arnold SM, Bukowski RM, Rothenberg ML, Cooper W, Wang KK, Gauthier E, Lockhart AC. A phase I dose escalation study of TTI-237 in patients with advanced malignant solid tumors. Invest New Drugs 2010; 30:266-72. [DOI: 10.1007/s10637-010-9506-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 07/23/2010] [Indexed: 11/24/2022]
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169
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In vitro assays to study the tracking of shortening microtubule ends and to measure associated forces. Methods Cell Biol 2010; 95:657-76. [PMID: 20466158 DOI: 10.1016/s0091-679x(10)95033-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
Accurate segregation of mitotic chromosomes relies in part on a strong linkage between the kinetochores and the plus ends of spindle microtubules (MTs). These attachments are maintained even as the MTs shorten from their kinetochore-associated ends, and despite the large variability in the magnitude of load from the chromosomal "cargo." Analysis of the underlying mechanisms has recently been facilitated by the identification and purification of various kinetochore complexes. In this chapter we review some existing approaches to study the interaction of these protein complexes with the ends of shortening MTs in vitro. Specifically, we describe the application of a "segmented" MT technique, which allows quantitative characterization of the tracking of the shortening MT ends by fluorescent proteins and protein-coated beads, as well as controlled measurement of the associated forces. There is a marked similarity between these methods and the approaches that are used to study the motions and forces produced by ATP-dependent motor enzymes walking on coverslip-attached, stable MTs. However, optical resolution at the shortening ends of coverslip-tethered MTs is not as good and the thermal noise is high. Furthermore, there are significant differences in the mechanisms of motions of microbeads driven by motors and by MT depolymerization, as well as in the interpretation of the resulting forces. Clearly, the depolymerization-driven motions are difficult to study and the corresponding phenomenology and theories are more complex than in the motors field. We hope, however, that the relatively straightforward assays based on "segmented" MTs, which are described below, will become a routine methodology, thereby helping to advance the studies of the MT-depolymerization-dependent motility.
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170
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Sarkar S, Haldar S, Hajra S, Sinha P. The budding yeast protein Sum1 functions independently of its binding partners Hst1 and Sir2 histone deacetylases to regulate microtubule assembly. FEMS Yeast Res 2010; 10:660-73. [PMID: 20608984 DOI: 10.1111/j.1567-1364.2010.00655.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The budding yeast protein Sum1 is a transcription factor that associates with the histone deacetylase Hst1p or, in its absence, with Sir2p to form repressed chromatin. In this study, SUM1 has been identified as an allele-specific dosage suppressor of mutations in the major alpha-tubulin-coding gene TUB1. When cloned in a 2mu vector, SUM1 suppressed the cold-sensitive and benomyl-hypersensitive phenotypes associated with the tub1-1 mutation. The suppression was Hst1p- and Sir2p-independent, suggesting that it was not mediated by deacetylation events associated with Sum1p when it functions along with its known partner histone deacetylases. This protein was confined to the nucleus, but did not colocalize with the microtubules nor did it bind to alpha- or beta-tubulin. Cells deleted of SUM1 showed hypersensitivity to benomyl and cold-sensitive growth, phenotypes exhibited by mutants defective in microtubule function and cytoskeletal defects. These observations suggest that Sum1p is a novel regulator of microtubule function. We propose that as a dosage suppressor, Sum1p promotes the formation of microtubules by increasing the availability of the alphabeta-heterodimer containing the mutant alpha-tubulin subunit.
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Affiliation(s)
- Sourav Sarkar
- Department of Biochemistry, Bose Institute, Kolkata, India
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171
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Chen L, Ma W, Wang X, Niu C, Lei C. Analysis of pupal head proteome and its alteration in diapausing pupae of Helicoverpa armigera. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:247-252. [PMID: 19852966 DOI: 10.1016/j.jinsphys.2009.10.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 10/14/2009] [Accepted: 10/14/2009] [Indexed: 05/28/2023]
Abstract
The proteomic approach has proven to be an useful tool for understanding insect diapause processes. Using 2D gel electrophoresis and matrix assisted laser/desorption ionization (MALDI) time of flight (TOF), we identified 24 proteins in the head of Helicoverpa armigera pupae with diverse functional characteristics, including cytoskeleton proteins, heat-shock proteins, insect development regulation factors, ATPases, proteins regulating signal pathway and enzymes involved in metabolism, etc. A proteomic comparison between nondiapausing and diapausing pupae revealed three proteins that were present only in nondiapausing pupae, and six proteins represented >or=2.0-fold or <or=0.5-fold changes. The differentially expressed proteins, including heat-shock protein 90, chitin deacetylase, alpha-tubulin and transitional endoplasmic reticulum ATPase, etc. were reported for the first time in H. armigera. Identification of these proteins will enable us to further characterize the regulated functions of diapause in this important species.
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Affiliation(s)
- Lizhen Chen
- Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science & Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
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172
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Peloruside A inhibits microtubule dynamics in a breast cancer cell line MCF7. Invest New Drugs 2010; 29:615-26. [PMID: 20169398 DOI: 10.1007/s10637-010-9398-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 01/27/2010] [Indexed: 12/27/2022]
Abstract
Peloruside A (PelA), a novel microtubule-stabilizing agent and potential anti-cancer drug, isolated from the marine sponge Mycale hentscheli, binds to a distinct, non-taxoid binding site on tubulin. Using live-cell confocal microscopy, the effects of PelA on microtubule dynamics were quantified in a human breast adenocarcinoma cell line (MCF7) stably expressing GFP-α-tubulin. Changes in microtubule length were tracked over time in cells treated with PelA concentrations ranging from 3.8-100 nM. As with other microtubule-targeting drugs like paclitaxel and epothilone B, microtubule dynamics were suppressed in a concentration-dependent manner. At the PelA IC₅₀ concentrations for cell proliferation (3.8 nM) and G₂/M block (25 nM), PelA inhibited dynamicity by 23% and 45%, respectively. At 25 nM PelA, effects included a 24% and 41% reduction in average growth rate and growth length, respectively. Additionally, the total time spent in pause increased by 53% and coincided with a 36% reduction in the average amount of time spent growing. Rescue and catastrophe frequencies were not significantly affected by PelA, except for length-based catastrophe (67% increase). The results provide further insight into PelA's unique mode of stabilization and contribute to our understanding of how microtubule-targeting agents exert their anti-mitotic effects.
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173
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Donovan D. Management of peripheral neuropathy caused by microtubule inhibitors. Clin J Oncol Nurs 2010; 13:686-94. [PMID: 19948466 DOI: 10.1188/09.cjon.686-694] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Any patient receiving an agent that targets microtubules (e.g., taxanes, vinca alkaloids, epothilones) is at some risk for encountering peripheral neuropathy. This article provides tools and discussion to aid nurses in managing peripheral neuropathy in their patients through early identification and education. Some patients are at higher risk than others based on their chemotherapeutic regimen, pretreatment history, and comorbidities. When interacting with at-risk patients, nurses should be alert for primarily sensory neuropathy that presents as loss of sensation, numbness, or tingling, beginning at the distal ends of the extremities and moving proximally with a stocking or glove distribution. Clinical assessments for neuropathy generally employ grading scales, questionnaires, quantitative sensory testing, and psychometric assessments; each has benefits and limitations. Patients who experience moderate or severe neuropathy may require a dose reduction or delay until symptoms resolve; these patients may need a lower dose for the next treatment cycle. No known agents have proven to prevent or treat severe neuropathy more effectively than regular neurologic examinations, early intervention, and patient education. In this respect, nurses can make a substantial difference in the impact of neuropathy on treatment efficacy and patients' quality of life.
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Affiliation(s)
- Diana Donovan
- Weill Cornell Breast Center, Cornell University, New York, NY, USA.
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174
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175
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Smith C. The ‘hard problem’ and the quantum physicists. Part 2: Modern times. Brain Cogn 2009; 71:54-63. [DOI: 10.1016/j.bandc.2007.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 08/19/2007] [Accepted: 09/13/2007] [Indexed: 11/24/2022]
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176
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Perez EA. Microtubule inhibitors: Differentiating tubulin-inhibiting agents based on mechanisms of action, clinical activity, and resistance. Mol Cancer Ther 2009; 8:2086-95. [PMID: 19671735 DOI: 10.1158/1535-7163.mct-09-0366] [Citation(s) in RCA: 372] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Microtubules are important cellular targets for anticancer therapy because of their key role in mitosis. Microtubule inhibitors (MTI) such as taxanes, vinca alkaloids, and epothilones stabilize or destabilize microtubules, thereby suppressing microtubule dynamics required for proper mitotic function, effectively blocking cell cycle progression and resulting in apoptosis. In spite of their antitumor activity, innate or acquired drug resistance to MTIs such as the taxanes is common, limiting their overall clinical efficacy. Further insight into the mechanisms of action of microtubule-targeting drugs has lead to the discovery of novel agents that may provide higher efficacy with limited toxicity and help overcome resistance to conventional MTIs. This review will focus on the different mechanisms of action of MTIs, potential factors related to resistance and tolerability, and will discuss the recent approval as well as the development of new antineoplastic agents.
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Affiliation(s)
- Edith A Perez
- Division of Hematology and Oncology, Mayo Clinic, Jacksonville, FL32224, USA.
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177
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Acetylated tubulin associates with the fifth cytoplasmic domain of Na(+)/K(+)-ATPase: possible anchorage site of microtubules to the plasma membrane. Biochem J 2009; 422:129-37. [PMID: 19476441 DOI: 10.1042/bj20082410] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We showed previously that NKA (Na(+)/K(+)-ATPase) interacts with acetylated tubulin resulting in inhibition of its catalytic activity. In the present work we determined that membrane-acetylated tubulin, in the presence of detergent, behaves as an entity of discrete molecular mass (320-400 kDa) during molecular exclusion chromatography. We also found that microtubules assembled in vitro are able to bind to NKA when incubated with a detergent-solubilized membrane preparation, and that isolated native microtubules have associated NKA. Furthermore, we determined that CD5 (cytoplasmic domain 5 of NKA) is capable of interacting with acetylated tubulin. Taken together, our results are consistent with the idea that NKA may act as a microtubule-plasma membrane anchorage site through an interaction between acetylated tubulin and CD5.
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178
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Obstacles on the microtubule reduce the processivity of Kinesin-1 in a minimal in vitro system and in cell extract. Biophys J 2009; 96:3341-53. [PMID: 19383477 DOI: 10.1016/j.bpj.2009.01.015] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 12/19/2008] [Accepted: 01/08/2009] [Indexed: 11/23/2022] Open
Abstract
Inside cells, a multitude of molecular motors and other microtubule-associated proteins are expected to compete for binding to a limited number of binding sites available on microtubules. Little is known about how competition for binding sites affects the processivity of molecular motors and, therefore, cargo transport, organelle positioning, and microtubule organization, processes that all depend on the activity of more or less processive motors. Very few studies have been performed in the past to address this question directly. Most studies reported only minor effects of crowding on the velocity of motors. However, a controversy appears to exist regarding the effect of crowding on motor processivity. Here, we use single-molecule imaging of mGFP-labeled minimal dimeric kinesin-1 constructs in vitro to study the effects of competition on kinesin's processivity. For competitors, we use kinesin rigor mutants as static roadblocks, minimal wild-type kinesins as motile obstacles, and a cell extract as a complex mixture of microtubule-associated proteins. We find that mGFP-labeled kinesin-1 detaches prematurely from microtubules when it encounters obstacles, leading to a strong reduction of its processivity, a behavior that is largely independent of the type of obstacle used here. Kinesin has a low probability to wait briefly when encountering roadblocks. Our data suggest, furthermore, that kinesin can occasionally pass obstacles on the protofilament track.
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179
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Kim M, Denlinger DL. Decrease in expression of beta-tubulin and microtubule abundance in flight muscles during diapause in adults of Culex pipiens. INSECT MOLECULAR BIOLOGY 2009; 18:295-302. [PMID: 19523062 DOI: 10.1111/j.1365-2583.2009.00870.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The cDNA encoding beta-tubulin in the mosquito Culex pipiens has high similarity with the beta-tubulins reported in other insects. In this study, we examine expression of this gene and microtubule abundance in relation to diapause and low temperature. While non-diapausing mosquitoes express beta-tubulin highly in their thoracic muscles, expression is quite low during adult diapause. The abundance of microtubules was also much lower in flight muscles of diapausing adults than in flight muscles from non-diapausing individuals, as confirmed by laser confocal microscopy of tubulins stained using indirect immunofluorescence. Low temperatures decreased microtubule abundance in midguts of non-diapausing mosquitoes, but microtubule abundance in diapausing mosquitoes was already low and remained unchanged by low temperature exposure. Overall, pixel intensity averages were higher in the flight muscles than in the midguts, and again low temperatures decreased microtubule abundance in the flight muscles of non-diapausing females, while levels remained consistently low in diapausing females. These results clearly indicate that a decrease in microtubule abundance is evoked both by the programming of diapause and, in non-diapausing females, by exposure to low temperatures. Quite possibly the reduced microtubule abundance in the flight muscles and reduced expression of beta-tubulin are functionally correlated to the reduction in flight activity that is associated with low temperature and diapause.
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Affiliation(s)
- M Kim
- Department of Entomology, The Ohio State University, Columbus, 43210, USA.
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180
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Cauwe B, Martens E, Proost P, Opdenakker G. Multidimensional degradomics identifies systemic autoantigens and intracellular matrix proteins as novel gelatinase B/MMP-9 substrates. Integr Biol (Camb) 2009; 1:404-26. [PMID: 20023747 DOI: 10.1039/b904701h] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The action radius of matrix metalloproteinases or MMPs is not restricted to massive extracellular matrix (ECM) degradation, it extends to the proteolysis of numerous secreted and membrane-bound proteins. Although many instances exist in which cells disintegrate, often in conjunction with induction of MMPs, the intracellular MMP substrate repertoire or degradome remains relatively unexplored. We started an unbiased exploration of the proteolytic modification of intracellular proteins by MMPs, using gelatinase B/MMP-9 as a model enzyme. To this end, multidimensional degradomics technology was developed by the integration of broadly available biotechniques. In this way, 100-200 MMP-9 candidate substrates were isolated, of which 69 were identified. Integration of these results with the known biological functions of the substrates revealed many novel MMP-9 substrates from the intracellular matrix (ICM), such as actin, tubulin, gelsolin, moesin, ezrin, Arp2/3 complex subunits, filamin B and stathmin. About 2/3 of the identified candidates were autoantigens described in multiple autoimmune conditions and in cancer (e.g. annexin I, nucleolin, citrate synthase, HMGB1, alpha-enolase, histidyl-tRNA synthetase, HSP27, HSC70, HSP90, snRNP D3). These findings led to the insight that MMPs and other proteases may have novel (immuno)regulatory properties by the clearance of toxic and immunogenic burdens of abundant ICM proteins released after extensive necrosis. In line with the extracellular processing of organ-specific autoantigens, proteolysis might also assist in the generation of immunodominant 'neo-epitopes' from systemic autoantigens. The study of proteolysis of ICM molecules, autoantigens, alarmins and other crucial intracellular molecules may result in the discovery of novel roles for proteolytic modification.
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Affiliation(s)
- Bénédicte Cauwe
- Department of Microbiology and Immunology, Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Minderbroedersstraat 10, Leuven, Belgium
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181
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Microtubule assembly, organization and dynamics in axons and dendrites. Nat Rev Neurosci 2009; 10:319-32. [PMID: 19377501 DOI: 10.1038/nrn2631] [Citation(s) in RCA: 762] [Impact Index Per Article: 50.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During the past decade enormous advances have been made in our understanding of the basic molecular machinery that is involved in the development of neuronal polarity. Far from being mere structural elements, microtubules are emerging as key determinants of neuronal polarity. Here we review the current understanding of the regulation of microtubule assembly, organization and dynamics in axons and dendrites. These studies provide new insight into microtubules' function in neuronal development and their potential contribution to plasticity.
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182
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Mulder AM, Glavis-Bloom A, Moores CA, Wagenbach M, Carragher B, Wordeman L, Milligan RA. A new model for binding of kinesin 13 to curved microtubule protofilaments. ACTA ACUST UNITED AC 2009; 185:51-7. [PMID: 19332892 PMCID: PMC2700504 DOI: 10.1083/jcb.200812052] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kinesin motor proteins use adenosine triphosphate hydrolysis to do work on microtubules (MTs). Most kinesins walk along the MT, but class 13 kinesins instead uniquely recognize MT ends and depolymerize MT protofilaments. We have used electron microscopy (EM) to understand the molecular interactions by which kinesin 13 performs these tasks. Although a construct of only the motor domain of kinesin 13 binds to every heterodimer of a tubulin ring, a construct containing the neck and the motor domain occupies alternate binding sites. Likewise, EM maps of the dimeric full-length (FL) protein exhibit alternate site binding but reveal density for only one of two motor heads. These results indicate that the second head of dimeric kinesin 13 does not have access to adjacent binding sites on the curved protofilament and suggest that the neck alone is sufficient to obstruct access. Additionally, the FL construct promotes increased stacking of rings compared with other constructs. Together, these data suggest a model for kinesin 13 depolymerization in which increased efficiency is achieved by binding of one kinesin 13 molecule to adjacent protofilaments.
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Affiliation(s)
- Anke M Mulder
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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183
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Nishiyama M, Kimura Y, Nishiyama Y, Terazima M. Pressure-induced changes in the structure and function of the kinesin-microtubule complex. Biophys J 2009; 96:1142-50. [PMID: 19186149 PMCID: PMC2716646 DOI: 10.1016/j.bpj.2008.10.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 10/21/2008] [Indexed: 11/26/2022] Open
Abstract
Kinesin-1 is an ATP-driven molecular motor that "walks" along a microtubule by working two heads in a "hand-over-hand" fashion. The stepping motion is well-coordinated by intermolecular interactions between the kinesin head and microtubule, and is sensitively changed by applied forces. We demonstrate that hydrostatic pressure works as an inhibitory action on kinesin motility. We developed a high-pressure microscope that enables the application of hydrostatic pressures of up to 200 MPa (2000 bar). Under high-pressure conditions, taxol-stabilized microtubules were shortened from both ends at the same speed. The sliding velocity of kinesin motors was reversibly changed by pressure, and reached half-maximal value at approximately 100 MPa. The pressure-velocity relationship was very close to the force-velocity relationship of single kinesin molecules, suggesting a similar inhibitory mechanism on kinesin motility. Further analysis showed that the pressure mainly affects the stepping motion, but not the ATP binding reaction. The application of pressure is thought to enhance the structural fluctuation and/or association of water molecules with the exposed regions of the kinesin head and microtubule. These pressure-induced effects could prevent kinesin motors from completing the stepping motion.
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Affiliation(s)
- Masayoshi Nishiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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184
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Translocation of incoming pseudorabies virus capsids to the cell nucleus is delayed in the absence of tegument protein pUL37. J Virol 2009; 83:3389-96. [PMID: 19144717 DOI: 10.1128/jvi.02090-08] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
After fusion of the envelope of herpesvirus particles with the host cell plasma membrane, incoming nucleocapsids are transported to nuclear pores. Inner tegument proteins pUL36, pUL37, and pUS3 remain attached to the nucleocapsid after entry and therefore might mediate interactions between the nucleocapsid and cellular microtubule-associated motor proteins during transport. To assay for the role of pUL37 in this process, we constructed a pUL37-deleted pseudorabies virus mutant, PrV-DeltaUL37/UL35GFP, which expresses a fusion protein of green fluorescent protein (GFP) and the nonessential small capsid protein pUL35, resulting in the formation of fluorescently labeled capsids. Confocal laser-scanning microscopy of rabbit kidney cells infected with PrV-DeltaUL37/UL35GFP revealed that, whereas penetration was not affected in the absence of pUL37, nuclear translocation of incoming particles was delayed by approximately 1 h compared to PrV-UL35GFP, but not abolished. In contrast, phenotypically complemented pUL37-containing virions of PrV-DeltaUL37/UL35GFP exhibited wild type-like entry kinetics. Thus, the presence of pUL37 is required for rapid nuclear translocation of incoming nucleocapsids.
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185
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Gertsch J, Meier S, Müller M, Altmann KH. Differential Effects of Natural Product Microtubule Stabilizers on Microtubule Assembly: Single Agent and Combination Studies with Taxol, Epothilone B, and Discodermolide. Chembiochem 2009; 10:166-75. [DOI: 10.1002/cbic.200800556] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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186
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Lee NPY, Cheng CY. Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 636:172-85. [PMID: 19856168 DOI: 10.1007/978-0-387-09597-4_10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.
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Affiliation(s)
- Nikki P Y Lee
- Department of Medicine and Surgery, University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
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187
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Altmann KH. Preclinical pharmacology and structure-activity studies of epothilones. FORTSCHRITTE DER CHEMIE ORGANISCHER NATURSTOFFE = PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS. PROGRES DANS LA CHIMIE DES SUBSTANCES ORGANIQUES NATURELLES 2009; 90:157-220. [PMID: 19209843 DOI: 10.1007/978-3-211-78207-1_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Karl-Heinz Altmann
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland.
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188
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Clinical Development of Ixabepilone and Other Epothilones in Patients with Advanced Solid Tumors. Oncologist 2008; 13:1207-23. [DOI: 10.1634/theoncologist.2008-0143] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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189
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The Tubulin Binding Mode of MT Stabilizing and Destabilizing Agents Studied by NMR. Top Curr Chem (Cham) 2008; 286:151-208. [DOI: 10.1007/128_2008_22] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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190
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Azarenko O, Okouneva T, Singletary KW, Jordan MA, Wilson L. Suppression of microtubule dynamic instability and turnover in MCF7 breast cancer cells by sulforaphane. Carcinogenesis 2008; 29:2360-8. [PMID: 18952594 DOI: 10.1093/carcin/bgn241] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Sulforaphane (SFN), a prominent isothiocyanate present in cruciferous vegetables, is believed to be responsible along with other isothiocyanates for the cancer preventive activity of such vegetables. SFN arrests mitosis, possibly by affecting spindle microtubule function. A critical property of microtubules is their rapid and time-sensitive growth and shortening dynamics (dynamic instability), and suppression of dynamics by antimitotic anticancer drugs (e.g. taxanes and the vinca alkaloids) is central to the anticancer mechanisms of such drugs. We found that at concentrations that inhibited proliferation and mitosis of MCF7-green fluorescent protein-alpha-tubulin breast tumor cells by approximately 50% (~15 microM), SFN significantly modified microtubule organization in arrested spindles without modulating the spindle microtubule mass, in a manner similar to that of much more powerful antimitotic drugs. By using quantitative fluorescence video microscopy, we determined that at its mitotic concentration required to inhibit mitosis by 50%, SFN suppressed the dynamic instability of the interphase microtubules in these cells, strongly reducing the rate and extent of growth and shortening and decreasing microtubule turnover, without affecting the polymer mass. SFN suppressed the dynamics of purified microtubules in a similar fashion at concentrations well below those required to depolymerize microtubules, indicating that the suppression of dynamic instability by SFN in cells is due to a direct effect on the microtubules. The results indicate that SFN arrests proliferation and mitosis by stabilizing microtubules in a manner weaker than but similar to more powerful clinically used antimitotic anticancer drugs and strongly support the hypothesis that inhibition of mitosis by microtubule stabilization is important for SFN's chemopreventive activity.
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Affiliation(s)
- Olga Azarenko
- Department of Molecular, Cellular, and Developmental Biology and the Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA
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191
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Verdier-Pinard P, Pasquier E, Xiao H, Burd B, Villard C, Lafitte D, Miller LM, Angeletti RH, Horwitz SB, Braguer D. Tubulin proteomics: towards breaking the code. Anal Biochem 2008; 384:197-206. [PMID: 18840397 DOI: 10.1016/j.ab.2008.09.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 09/12/2008] [Accepted: 09/15/2008] [Indexed: 01/02/2023]
Affiliation(s)
- Pascal Verdier-Pinard
- INSERM UMR 911 CRO2, Aix-Marseille Université, Faculté de Pharmacie, 27 bd Jean Moulin, 13285 Marseille cedex 05, France.
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192
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Jordan MA, Horwitz SB, Lobert S, Correia JJ. Exploring the mechanisms of action of the novel microtubule inhibitor vinflunine. Semin Oncol 2008; 35:S6-S12. [PMID: 18538179 DOI: 10.1053/j.seminoncol.2008.01.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microtubules have been identified as a suitable target for anticancer therapy, primarily based on their biological importance in coordinating chromosomal segregation at mitosis. Two main classes of microtubule-targeted agents, the taxanes and vinca alkaloids, suppress the dynamic behavior of spindle microtubules, inducing mitotic arrest and subsequent apoptotic cell death. Clinical activity of taxanes and first-generation vinca alkaloids in the treatment of solid tumors and hematologic malignancies, respectively, has prompted further research for novel analogs with improved clinical efficacy and safety. Such efforts have led to the development of vinflunine, a bifluorinated vinca alkaloid endowed with unique antitumor properties. Highlighted in this review are the key features of vinflunine that lead to effective suppression of microtubule dynamics and induction of cell death in cancer cells.
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Affiliation(s)
- Mary Ann Jordan
- Department of Molecular, Cellular and Developmental Biology, University of California-Santa Barbara, Santa Barbara, CA 93106, USA.
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Doudican N, Rodriguez A, Osman I, Orlow SJ. Mebendazole induces apoptosis via Bcl-2 inactivation in chemoresistant melanoma cells. Mol Cancer Res 2008; 6:1308-15. [PMID: 18667591 DOI: 10.1158/1541-7786.mcr-07-2159] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Most metastatic melanoma patients fail to respond to available therapy, underscoring the need for novel approaches to identify new effective treatments. In this study, we screened 2,000 compounds from the Spectrum Library at a concentration of 1 micromol/L using two chemoresistant melanoma cell lines (M-14 and SK-Mel-19) and a spontaneously immortalized, nontumorigenic melanocyte cell line (melan-a). We identified 10 compounds that inhibited the growth of the melanoma cells yet were largely nontoxic to melanocytes. Strikingly, 4 of the 10 compounds (mebendazole, albendazole, fenbendazole, and oxybendazole) are benzimidazoles, a class of structurally related, tubulin-disrupting drugs. Mebendazole was prioritized to further characterize its mechanism of melanoma growth inhibition based on its favorable pharmacokinetic profile. Our data reveal that mebendazole inhibits melanoma growth with an average IC(50) of 0.32 micromol/L and preferentially induces apoptosis in melanoma cells compared with melanocytes. The intrinsic apoptotic response is mediated through phosphorylation of Bcl-2, which occurs rapidly after treatment with mebendazole in melanoma cells but not in melanocytes. Phosphorylation of Bcl-2 in melanoma cells prevents its interaction with proapoptotic Bax, thereby promoting apoptosis. We further show that mebendazole-resistant melanocytes can be sensitized through reduction of Bcl-2 protein levels, showing the essential role of Bcl-2 in the cellular response to mebendazole-mediated tubulin disruption. Our results suggest that this screening approach is useful for identifying agents that show promise in the treatment of even chemoresistant melanoma and identifies mebendazole as a potent, melanoma-specific cytotoxic agent.
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Affiliation(s)
- Nicole Doudican
- New York University School of Medicine, New York, NY 10016, USA
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Abstract
Microtubules play a number of important mechanical roles in almost all cell types in nearly all major phylogenetic trees. We have used a molecular mechanics approach to perform tensile tests on individual tubulin monomers and determined values for the axial and circumferential moduli for all currently known complete sequences. The axial elastic moduli, in vacuo, were found to be 1.25 GPa and 1.34 GPa for alpha- and beta-bovine tubulin monomers. In the circumferential direction, these moduli were 378 MPa for alpha- and 460 MPa for beta-structures. Using bovine tubulin as a template, 269 homologous tubulin structures were also subjected to simulated tensile loads yielding an average axial elastic modulus of 1.10 +/- 0.14 GPa for alpha-tubulin structures and 1.39 +/- 0.68 GPa for beta-tubulin. Circumferentially the alpha- and beta-moduli were 936 +/- 216 MPa and 658 +/- 134 MPa, respectively. Our primary finding is that that the axial elastic modulus of tubulin diminishes as the length of the monomer increases. However, in the circumferential direction, no correlation exists. These predicted anisotropies and scale dependencies may assist in interpreting the macroscale behavior of microtubules during mitosis or cell growth. Additionally, an intergenomic approach to investigating the mechanical properties of proteins may provide a way to elucidate the evolutionary mechanical constraints imposed by nature upon individual subcellular components.
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195
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Zuckerman ST, Kao WJ. LC/MS identification of 12 intracellular cytoskeletal and inflammatory proteins from monocytes adherent on surface-adsorbed fibronectin-derived peptides. J Biomed Mater Res A 2008; 85:513-29. [PMID: 17729253 PMCID: PMC5578865 DOI: 10.1002/jbm.a.31306] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The extent and duration of the host response determines device efficacy, yet the mechanism is poorly understood. U937 promonocytic cells were cultured on peptide-adsorbed tissue-culture polystyrene to better understand surface-modulated intracellular events. Phosphotyrosine proteins were enriched by immunoprecipitation and analyzed by nanospray HPLC-coupled tandem mass spectrometry (LC/MS). Tyrosine-phosphorylated proteins were chosen based on physiological significance and previous densitometry results, which identified a set of proteins ranging from approximately 200 to approximately 23 kDa showing altered phosphorylation levels in response to various surface-adsorbed ligands and phosphorylation inhibitor AG18. Although LC/MS has been used for nearly a decade, its application to the field of biomaterials is relatively novel. Twelve intracellular proteins identified by nanospray LC/MS are potentially related to the host response. Eight of the twelve proteins are related to the cytoskeleton including: moesin, heat shock protein 90beta, alpha-tubulin, elongation factor 1alpha, beta actin, vimentin, plasminogen activator inhibitor 2, and heterogeneous ribonuclear protein A2. The remaining four proteins: high mobility group box 1, caspase recruitment domain 5, glycoprotein 96, and heterogeneous nuclear ribonucleoprotein D0 modulate inflammation. The specific effect each peptide has upon modulating the phosphorylation state of these proteins cannot be determined from this work; however, 12 viable targets have been identified for further investigation into the role each plays in the surface-mediated monocyte response.
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Affiliation(s)
- Sean T. Zuckerman
- Department of Biomedical Engineering, University of Wisconsin-Madison, WI, 53705 USA
- School of Pharmacy, University of Wisconsin-Madison, WI, 53705 USA
| | - Weiyuan John Kao
- Department of Biomedical Engineering, University of Wisconsin-Madison, WI, 53705 USA
- School of Pharmacy, University of Wisconsin-Madison, WI, 53705 USA
- Correspondence should be addressed to 777 Highland Ave., University of Wisconsin-Madison, Madison, WI 53705. Tel: 608 263-2998, Fax: 608 262-5345,
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197
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Abstract
Small-molecule inhibition of the direct protein-protein interactions that mediate many important biological processes is an emerging and challenging area in drug design. Conventional drug design has mainly focused on the inhibition of a single protein, usually an enzyme or receptor, since these proteins often contain a clearly defined ligand-binding site with which a small-molecule drug can be designed to interact. Designing a small molecule to bind to a protein-protein interface and subsequently inhibit the interaction poses several challenges, including the initial identification of suitable protein-protein interactions, the surface area of the interface (it is often large), and the location of 'hot spots' (small regions suitable for drug binding). This article reviews the general approach to designing inhibitors of protein-protein interactions, and then focuses on recent advances in the use of small molecules targeted against a variety of protein-protein interactions that have therapeutic potential for cancer.
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198
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Schulze H, Dose M, Korpal M, Meyer I, Italiano JE, Shivdasani RA. RanBP10 is a cytoplasmic guanine nucleotide exchange factor that modulates noncentrosomal microtubules. J Biol Chem 2008; 283:14109-19. [PMID: 18347012 DOI: 10.1074/jbc.m709397200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Microtubule spindle assembly in mitosis is stimulated by Ran.GTP, which is generated along condensed chromosomes by the guanine nucleotide exchange factor (GEF) RCC1. This relationship suggests that similar activities might modulate other microtubule structures. Interphase microtubules usually extend from the centrosome, although noncentrosomal microtubules function in some differentiated cells, including megakaryocytes. In these cells, platelet biogenesis requires massive mobilization of microtubules in the cell periphery, where they form proplatelets, the immediate precursors of platelets, in the apparent absence of centrioles. Here we identify a cytoplasmic Ran-binding protein, RanBP10, as a factor that binds beta-tubulin and associates with megakaryocyte microtubules. Unexpectedly, RanBP10 harbors GEF activity toward Ran. A point mutation in the candidate GEF domain abolishes exchange activity, and our results implicate RanBP10 as a localized cytoplasmic Ran-GEF. RNA interference-mediated loss of RanBP10 in cultured megakaryocytes disrupts microtubule organization. These results lead us to propose that spatiotemporally restricted generation of cytoplasmic Ran.GTP may influence organization of the specialized microtubules required in thrombopoiesis and that RanBP10 might serve as a molecular link between Ran and noncentrosomal microtubules.
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199
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Layden BT, Saengsawang W, Donati RJ, Yang S, Mulhearn DC, Johnson ME, Rasenick MM. Structural model of a complex between the heterotrimeric G protein, Gsalpha, and tubulin. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:964-73. [PMID: 18373982 DOI: 10.1016/j.bbamcr.2008.02.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Revised: 02/11/2008] [Accepted: 02/13/2008] [Indexed: 11/17/2022]
Abstract
A number of studies have demonstrated interplay between the cytoskeleton and G protein signaling. Many of these studies have determined a specific interaction between tubulin, the building block of microtubules, and G proteins. The alpha subunits of some heterotrimeric G proteins, including Gsalpha, have been shown to interact strongly with tubulin. Binding of Galpha to tubulin results in increased dynamicity of microtubules due to activation of GTPase of tubulin. Tubulin also activates Gsalpha via a direct transfer of GTP between these molecules. Structural insight into the interaction between tubulin and Gsalpha was required, and was determined, in this report, through biochemical and molecular docking techniques. Solid phase peptide arrays suggested that a portion of the amino terminus, alpha2-beta4 (the region between switch II and switch III) and alpha3-beta5 (just distal to the switch III region) domains of Gsalpha are important for interaction with tubulin. Molecular docking studies revealed the best-fit models based on the biochemical data, showing an interface between the two molecules that includes the adenylyl cyclase/Gbetagamma interaction regions of Gsalpha and the exchangeable nucleotide-binding site of tubulin. These structural models explain the ability of tubulin to facilitate GTP exchange on Galpha and the ability of Galpha to activate tubulin GTPase.
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Affiliation(s)
- Brian T Layden
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Moores CA, Milligan RA. Visualisation of a kinesin-13 motor on microtubule end mimics. J Mol Biol 2008; 377:647-54. [PMID: 18294653 DOI: 10.1016/j.jmb.2008.01.079] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 01/17/2008] [Accepted: 01/23/2008] [Indexed: 11/25/2022]
Abstract
An expanding collection of proteins localises to microtubule ends to regulate cytoskeletal dynamics and architecture by unknown molecular mechanisms. Electron microscopy is invaluable for studying microtubule structure, but because microtubule ends are heterogeneous, their structures are difficult to determine. We therefore investigated whether tubulin oligomers induced by the drug dolastatin could mimic microtubule ends. The microtubule end-dependent ATPase of kinesin-13 motors is coupled to microtubule depolymerisation. Significantly, kinesin-13 motor ATPase activity is stimulated by dolastatin-tubulin oligomers, suggesting, first, that these oligomers share properties with microtubule ends and, second, that the physical presence of an end is less important than terminal tubulin flexibility for microtubule end recognition by the kinesin-13 motor. Using electron microscopy, we visualised the kinesin-13 motor-dolastatin-tubulin oligomer interaction in nucleotide states mimicking steps in the ATPase cycle. This enabled us to detect conformational changes that the motor undergoes during depolymerisation. Our data suggest that such tubulin oligomers can be used to examine other microtubule end-binding proteins.
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Affiliation(s)
- Carolyn A Moores
- School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK.
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