101
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Niethammer P, Kronja I, Kandels-Lewis S, Rybina S, Bastiaens P, Karsenti E. Discrete states of a protein interaction network govern interphase and mitotic microtubule dynamics. PLoS Biol 2007; 5:e29. [PMID: 17227146 PMCID: PMC1769425 DOI: 10.1371/journal.pbio.0050029] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Accepted: 11/28/2006] [Indexed: 11/23/2022] Open
Abstract
The cytoplasm of eukaryotic cells is thought to adopt discrete “states” corresponding to different steady states of protein networks that govern changes in subcellular organization. For example, in Xenopus eggs, the interphase to mitosis transition is induced solely by activation of cyclin-dependent kinase 1 (CDK1) that phosphorylates many proteins leading to a reorganization of the nucleus and assembly of the mitotic spindle. Among these changes, the large array of stable microtubules that exists in interphase is replaced by short, highly dynamic microtubules in metaphase. Using a new visual immunoprecipitation assay that quantifies pairwise protein interactions in a non-perturbing manner in Xenopus egg extracts, we reveal the existence of a network of interactions between a series of microtubule-associated proteins (MAPs). In interphase, tubulin interacts with XMAP215, which is itself interacting with XKCM1, which connects to APC, EB1, and CLIP170. In mitosis, tubulin interacts with XMAP215, which is connected to EB1. We show that in interphase, microtubules are stable because the catastrophe-promoting activity of XKCM1 is inhibited by its interactions with the other MAPs. In mitosis, microtubules are short and dynamic because XKCM1 is free and has a strong destabilizing activity. In this case, the interaction of XMAP215 with EB1 is required to counteract the strong activity of XKCM1. This provides the beginning of a biochemical description of the notion of “cytoplasmic states” regarding the microtubule system. When eukaryotic cells undergo cell division, a dramatic reorganization occurs during the transition from interphase to metaphase. The cell rounds up, chromosomes condense, the nuclear envelope breaks down, and microtubules (proteins that help maintain the cell's shape) become very short and dynamic before assembly of the mitotic spindle (the structure that pulls chromosomes apart). Although it is known that the CDK1 kinase induces this reorganization, the precise mechanisms that regulate such coordinated changes are not yet understood. To investigate the regulation of microtubule dynamics, we applied a new method, called visual immunoprecipitation (VIP), that enables simultaneous visualization of multiple protein interactions in cell extracts. There are two known major regulators of microtubule dynamics: a stabilizer (XMAP215) and a destabilizer (XKCM1); a series of other molecules (EB1, APC, and CLIP 170) are also involved, although their roles in the global regulation of microtubule dynamic instability are not as clear. We show here that microtubules are stable during interphase because the destabilizer is inhibited by the other molecules. During mitosis, however, the destabilizer is released, triggering the alteration of microtubule structure and dynamics. Thus, microtubule dynamics change in response to a dramatic switch in the interactions of a set of proteins. Previously unknown interactions between different microtubule-associated proteins (MAPs) are identified via a new technique, termed visual immunoprecipitation.
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Affiliation(s)
- Philipp Niethammer
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Iva Kronja
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Stefanie Kandels-Lewis
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Sonja Rybina
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Philippe Bastiaens
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail: (PB); (EK)
| | - Eric Karsenti
- Cell Biology and Biophysics Department, European Molecular Biology Laboratory, Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail: (PB); (EK)
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102
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Shaw RM, Fay AJ, Puthenveedu MA, von Zastrow M, Jan YN, Jan LY. Microtubule plus-end-tracking proteins target gap junctions directly from the cell interior to adherens junctions. Cell 2007; 128:547-60. [PMID: 17289573 PMCID: PMC1955433 DOI: 10.1016/j.cell.2006.12.037] [Citation(s) in RCA: 380] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 06/20/2006] [Accepted: 12/06/2006] [Indexed: 10/23/2022]
Abstract
Gap junctions are intercellular channels that connect the cytoplasms of adjacent cells. For gap junctions to properly control organ formation and electrical synchronization in the heart and the brain, connexin-based hemichannels must be correctly targeted to cell-cell borders. While it is generally accepted that gap junctions form via lateral diffusion of hemichannels following microtubule-mediated delivery to the plasma membrane, we provide evidence for direct targeting of hemichannels to cell-cell junctions through a pathway that is dependent on microtubules; through the adherens-junction proteins N-cadherin and beta-catenin; through the microtubule plus-end-tracking protein (+TIP) EB1; and through its interacting protein p150(Glued). Based on live cell microscopy that includes fluorescence recovery after photobleaching (FRAP), total internal reflection fluorescence (TIRF), deconvolution, and siRNA knockdown, we propose that preferential tethering of microtubule plus ends at the adherens junction promotes delivery of connexin hemichannels directly to the cell-cell border. These findings support an unanticipated mechanism for protein delivery to points of cell-cell contact.
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Affiliation(s)
- Robin M. Shaw
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, CA 94143
| | - Alex J. Fay
- Graduate Group in Biophysics, University of California, San Francisco, CA 94143
| | - Manojkumar A. Puthenveedu
- Departments of Psychiatry and Cellular & Molecular Pharmacology, University of California, San Francisco, CA 94143
| | - Mark von Zastrow
- Departments of Psychiatry and Cellular & Molecular Pharmacology, University of California, San Francisco, CA 94143
| | - Yuh-Nung Jan
- Howard Hughes Medical Institute and Departments of Physiology and Biochemistry, University of California, San Francisco, CA 94143, USA
| | - Lily Y. Jan
- Howard Hughes Medical Institute and Departments of Physiology and Biochemistry, University of California, San Francisco, CA 94143, USA
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103
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Gu C, Zhou W, Puthenveedu MA, Xu M, Jan YN, Jan LY. The Microtubule Plus-End Tracking Protein EB1 Is Required for Kv1 Voltage-Gated K+ Channel Axonal Targeting. Neuron 2006; 52:803-16. [PMID: 17145502 DOI: 10.1016/j.neuron.2006.10.022] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Revised: 12/29/2005] [Accepted: 10/20/2006] [Indexed: 01/25/2023]
Abstract
Axonal Kv1 channels regulate action potential propagation-an evolutionarily conserved function important for the control of motor behavior as evidenced from the linkage of human Kv1 channel mutations to myokymia/episodic ataxia type 1 (EA1) and the Shaker mutant phenotype in Drosophila. To search for the machinery that mediates axonal targeting of Kv1 channels composed of both alpha and beta subunits, we first demonstrate that Kvbeta2 is responsible for targeting Kv1 channels to the axon. Next, we show that Kvbeta2 axonal targeting depends on its ability to associate with the microtubule (MT) plus-end tracking protein (+TIP) EB1. Not only do Kvbeta2 and EB1 move in unison down the axon, Brefeldin A-sensitive Kv1-containing vesicles can also be found at microtubule ends near the cell membrane. In addition, we found that Kvbeta2 associates with KIF3/kinesin II as well. Indeed, Kv1 channels rely on both KIF3/kinesin II and EB1 for their axonal targeting.
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Affiliation(s)
- Chen Gu
- Howard Hughes Medical Institute, Departments of Physiology and Biochemistry, University of California, San Francisco, San Francisco, California 94143, USA.
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104
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Honnappa S, Okhrimenko O, Jaussi R, Jawhari H, Jelesarov I, Winkler FK, Steinmetz MO. Key interaction modes of dynamic +TIP networks. Mol Cell 2006; 23:663-71. [PMID: 16949363 DOI: 10.1016/j.molcel.2006.07.013] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 06/27/2006] [Accepted: 07/13/2006] [Indexed: 11/22/2022]
Abstract
Dynamic microtubule plus-end tracking protein (+TIP) networks are implicated in all functions of microtubules, but the molecular determinants of their interactions are largely unknown. Here, we have explored key binding modes of +TIPs by analyzing the interactions between selected CAP-Gly, EB-like, and carboxy-terminal EEY/F-COO(-) sequence motifs. X-ray crystallography and biophysical binding studies demonstrate that the beta2-beta3 loop of CAP-Gly domains determines EB-like motif binding specificity. They further show how CAP-Gly domains serve as recognition domains for EEY/F-COO(-) motifs, which represent characteristic and functionally important sequence elements in EB, CLIP-170, and alpha-tubulin. Our findings provide a molecular basis for understanding the modular interaction modes between alpha-tubulin, CLIPs, EB proteins, and the dynactin-dynein motor complex and suggest that multiple low-affinity binding sites in different combinations control dynamic +TIP networks at microtubule ends. They further offer insights into the structural consequences of genetic CAP-Gly domain defects found in severe human disorders.
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Affiliation(s)
- Srinivas Honnappa
- Biomolecular Research, Structural Biology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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105
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Peris L, Thery M, Fauré J, Saoudi Y, Lafanechère L, Chilton JK, Gordon-Weeks P, Galjart N, Bornens M, Wordeman L, Wehland J, Andrieux A, Job D. Tubulin tyrosination is a major factor affecting the recruitment of CAP-Gly proteins at microtubule plus ends. ACTA ACUST UNITED AC 2006; 174:839-49. [PMID: 16954346 PMCID: PMC2064338 DOI: 10.1083/jcb.200512058] [Citation(s) in RCA: 256] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Tubulin-tyrosine ligase (TTL), the enzyme that catalyzes the addition of a C-terminal tyrosine residue to α-tubulin in the tubulin tyrosination cycle, is involved in tumor progression and has a vital role in neuronal organization. We show that in mammalian fibroblasts, cytoplasmic linker protein (CLIP) 170 and other microtubule plus-end tracking proteins comprising a cytoskeleton-associated protein glycine-rich (CAP-Gly) microtubule binding domain such as CLIP-115 and p150 Glued, localize to the ends of tyrosinated microtubules but not to the ends of detyrosinated microtubules. In vitro, the head domains of CLIP-170 and of p150 Glued bind more efficiently to tyrosinated microtubules than to detyrosinated polymers. In TTL-null fibroblasts, tubulin detyrosination and CAP-Gly protein mislocalization correlate with defects in both spindle positioning during mitosis and cell morphology during interphase. These results indicate that tubulin tyrosination regulates microtubule interactions with CAP-Gly microtubule plus-end tracking proteins and provide explanations for the involvement of TTL in tumor progression and in neuronal organization.
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Affiliation(s)
- Leticia Peris
- Laboratoire du Cytosquelette, Institut National de la Santé et de la Recherche Médicale U366, Département Réponse et Dynamique Cellulaire, Commisariat à l'Energie Atomique Grenoble, 38054 Grenoble, France
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106
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Watson P, Stephens DJ. Microtubule plus-end loading of p150(Glued) is mediated by EB1 and CLIP-170 but is not required for intracellular membrane traffic in mammalian cells. J Cell Sci 2006; 119:2758-67. [PMID: 16772339 PMCID: PMC1630633 DOI: 10.1242/jcs.02999] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microtubule dynamics and function are regulated, at least in part, by a family of proteins that localize to microtubule plus-ends, and include EB1, CLIP-170 and the dynactin component p150(Glued). Plus-end pools of these proteins, notably dynactin, have been invoked in a number of ;search-and-capture' mechanisms, including the attachment of microtubules to kinetochores during mitosis and to endomembranes prior to the initiation of intracellular transport. Here we show that, in mammalian cells, EB1 is required for the plus-end localization of CLIP-170, and that this is in turn required to localize p150(Glued) to plus-ends. Specific depletion of CLIP-170 results in defects in microtubule dynamics, cell polarization in response to scratch wounding and a loss of p150(Glued) from plus ends. By contrast, removal of p150(Glued) from plus-ends by depletion of either EB1 or CLIP-170 caused no defects in the localization of intracellular organelles, the dynamics of ER-to-Golgi transport, the efficiency of transferrin uptake or the motility of early endosomes or lysosomes. In addition to labelling microtubule plus-ends, we show that GFP-p150(Glued) becomes incorporated into the dynactin complex and labels small, highly dynamic, punctate structures that move along microtubules. A subset of these structures colocalizes with ER-Golgi transport intermediates. Together, these data show that the function of CLIP-170 and p150(Glued) in membrane trafficking is not associated with their plus-end localization.
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Affiliation(s)
- Peter Watson
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK
| | - David J. Stephens
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK
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107
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Levy JR, Sumner CJ, Caviston JP, Tokito MK, Ranganathan S, Ligon LA, Wallace KE, LaMonte BH, Harmison GG, Puls I, Fischbeck KH, Holzbaur ELF. A motor neuron disease-associated mutation in p150Glued perturbs dynactin function and induces protein aggregation. ACTA ACUST UNITED AC 2006; 172:733-45. [PMID: 16505168 PMCID: PMC2063705 DOI: 10.1083/jcb.200511068] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The microtubule motor cytoplasmic dynein and its activator dynactin drive vesicular transport and mitotic spindle organization. Dynactin is ubiquitously expressed in eukaryotes, but a G59S mutation in the p150Glued subunit of dynactin results in the specific degeneration of motor neurons. This mutation in the conserved cytoskeleton-associated protein, glycine-rich (CAP-Gly) domain lowers the affinity of p150Glued for microtubules and EB1. Cell lines from patients are morphologically normal but show delayed recovery after nocodazole treatment, consistent with a subtle disruption of dynein/dynactin function. The G59S mutation disrupts the folding of the CAP-Gly domain, resulting in aggregation of the p150Glued protein both in vitro and in vivo, which is accompanied by an increase in cell death in a motor neuron cell line. Overexpression of the chaperone Hsp70 inhibits aggregate formation and prevents cell death. These data support a model in which a point mutation in p150Glued causes both loss of dynein/dynactin function and gain of toxic function, which together lead to motor neuron cell death.
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Affiliation(s)
- Jennifer R Levy
- Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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108
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Hashimoto T, Kato T. Cortical control of plant microtubules. CURRENT OPINION IN PLANT BIOLOGY 2006; 9:5-11. [PMID: 16324879 DOI: 10.1016/j.pbi.2005.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Accepted: 11/20/2005] [Indexed: 05/05/2023]
Abstract
The cortical microtubule array of plant cells appears in early G(1) and remodels during the progression of the cell cycle and differentiation, and in response to various stimuli. Recent studies suggest that cortical microtubules are mostly formed on pre-existing microtubules and, after detachment from the initial nucleation sites, actively interact with each other to attain distinct distribution patterns. The plus end of growing microtubules is thought to accumulate protein complexes that regulate both microtubule dynamics and interactions with cortical targets. The ROP family of small GTPases and the mitogen-activated protein kinase pathways have emerged as key players that mediate the cortical control of plant microtubules.
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Affiliation(s)
- Takashi Hashimoto
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.
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109
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Ligon LA, Shelly SS, Tokito MK, Holzbaur EL. Microtubule binding proteins CLIP-170, EB1, and p150Glued form distinct plus-end complexes. FEBS Lett 2006; 580:1327-32. [PMID: 16455083 PMCID: PMC1550970 DOI: 10.1016/j.febslet.2006.01.050] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 01/13/2006] [Accepted: 01/17/2006] [Indexed: 11/29/2022]
Abstract
Microtubule plus-end proteins CLIP-170 and EB1 dynamically track the tips of growing microtubules in vivo. Here we examine the association of these proteins with microtubules in vitro. CLIP-170 binds tubulin dimers and co-assembles into growing microtubules. EB1 binds tubulin dimers more weakly, so no co-assembly is observed. However, EB1 binds to CLIP-170, and forms a co-complex with CLIP-170 and tubulin that is recruited to growing microtubule plus ends. The interaction between CLIP-170 and EB1 is competitively inhibited by the related CAP-Gly protein p150Glued, which also localizes to microtubule plus ends in vivo. Based on these observations, we propose a model in which the formation of distinct plus-end complexes may differentially affect microtubule dynamics in vivo.
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Affiliation(s)
| | | | | | - Erika L.F. Holzbaur
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, Tel. 215-573-3257; Fax 215-573-5851; Email
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110
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Miller RK, D'Silva S, Moore JK, Goodson HV. The CLIP-170 orthologue Bik1p and positioning the mitotic spindle in yeast. Curr Top Dev Biol 2006; 76:49-87. [PMID: 17118263 DOI: 10.1016/s0070-2153(06)76002-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Bik1p is the yeast Saccharomyces cerevisiae representative of the CLIP-170 family of microtubule plus-end tracking proteins. Bik1p shares a number of similarities with its mammalian counterpart CLIP-170, including an important role in dynein function. However, Bik1p and CLIP-170 differ in several significant ways, including the mechanisms utilized to track microtubule plus ends. In addition to presenting functional comparisons between Bik1p and CLIP-170, we provide sequence analyses that reveal previously unrecognized similarities between Bik1p and its animal counterparts. We examine in detail what is known about the functions of Bik1p and consider the various roles that Bik1p plays in positioning the yeast mitotic spindle. This chapter also highlights several recent findings, including the contribution of Bik1p to the yeast mating pathway.
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Affiliation(s)
- Rita K Miller
- Department of Biology, University of Rochester Rochester, New York 14627, USA
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111
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Yan X, Habedanck R, Nigg EA. A complex of two centrosomal proteins, CAP350 and FOP, cooperates with EB1 in microtubule anchoring. Mol Biol Cell 2005; 17:634-44. [PMID: 16314388 PMCID: PMC1356575 DOI: 10.1091/mbc.e05-08-0810] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The anchoring of microtubules (MTs) to subcellular structures is critical for cell shape, polarity, and motility. In mammalian cells, the centrosome is a prominent MT anchoring structure. A number of proteins, including ninein, p150Glued, and EB1, have been implicated in centrosomal MT anchoring, but the process is far from understood. Here we show that CAP350 and FOP (FGFR1 oncogene partner) form a centrosomal complex required for MT anchoring. We show that the C-terminal domain of CAP350 interacts directly with FOP and that both proteins localize to the centrosome throughout the cell cycle. FOP also binds to EB1 and is required for localizing EB1 to the centrosome. Depletion of either CAP350, FOP, or EB1 by siRNA causes loss of MT anchoring and profound disorganization of the MT network. These results have implications for the mechanisms underlying MT anchoring at the centrosome and they attribute a key MT anchoring function to two novel centrosomal proteins, CAP350 and FOP.
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Affiliation(s)
- Xiumin Yan
- Department of Cell Biology, Max-Planck-Institute of Biochemistry, D-82152 Martinsried, Germany
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