151
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Abstract
How do cells regulate centrosome number? A canonical duplication cycle generates two centrosomes from one in most proliferating cells. Centrioles are key to this process, and molecules such as centrins, SAS-4 and ZYG-1 govern daughter centriole formation. Cdk2 activity probably couples centrosome duplication with the S phase, and a licensing mechanism appears to limit centrosome duplication to once per cell cycle. However, such mechanisms must be altered in some cells – for example, spermatocytes – in which centrosome duplication and DNA replication are uncoupled. There are also alternative pathways of centrosome biogenesis. For example, one centrosome is reconstituted from two gametes at fertilization; in this case, the most common strategy involves differential contributions of centrioles and pericentriolar material (PCM) from each gamete. Furthermore, centrioles can sometimes form de novo from no apparent template. This occurs, for instance, in the early mouse embryo and in parthenogenetic species and might rely on a pre-existing seed that resides within PCM but is not visible by ultrastructural analysis.
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Affiliation(s)
- Marie Delattre
- Swiss Institute for Experimental Cancer Research (ISREC), CH-1066 Epalinges/Lausanne, Switzerland
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152
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Affiliation(s)
- Iain A Drummond
- Department of Medicine, Harvard Medical School and Renal Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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153
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Ou Y, Rattner JB. The Centrosome in Higher Organisms: Structure, Composition, and Duplication. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 238:119-82. [PMID: 15364198 DOI: 10.1016/s0074-7696(04)38003-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The centrosome found in higher organisms is an organelle with a complex and dynamic architecture and composition. This organelle not only functions as a microtubule-organizing center, but also is integrated with or impacts a number of cellular processes. Defects associated with this organelle have been linked to a variety of human diseases including several forms of cancer. Here we review the emerging picture of how the structure, composition, duplication, and function of the centrosome found in higher organisms are interrelated.
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Affiliation(s)
- Young Ou
- Department of Cell Biology and Anatomy, University of Calgary 3330 Hospital Drive NW, Calgary, Alberta, Canada
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154
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Yoo JC, Chang JR, Kim SH, Jang SK, Wolgemuth DJ, Kim K, Rhee K. NIP1/XB51/NECAB3 is a potential substrate of Nek2, suggesting specific roles of Nek2 in Golgi. Exp Cell Res 2004; 292:393-402. [PMID: 14697346 DOI: 10.1016/j.yexcr.2003.09.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nek2 is a mammalian protein kinase structurally homologous to Aspergillus NIMA. We previously observed that the Nek2 protein was localized in multiple sites within a cell in a cell cycle stage-specific manner. Such dynamic behavior of Nek2 allowed us to propose that Nek2 may be a mitotic regulator that is involved in diverse cell cycle events. To better understand the cellular processes in which Nek2 participates, we carried out yeast two-hybrid screening and isolated Nek2-Interacting Protein 1 (NIP1), which has been also named as XB51 and NECAB3. Physical interactions of Nek2 with NIP1 were confirmed. In fact, Nek2 can phosphorylate NIP1 in vivo. Immunostaining experiments revealed that NIP1 is a Golgi protein. These results propose a possible involvement of Nek2 in biological processes of the Golgi body, perhaps in relation to the inheritance of Golgi during mitosis or to cell cycle stage-specific regulation of exocytosis.
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Affiliation(s)
- Jae Cheal Yoo
- School of Biological Sciences, Seoul National University, Seoul, 151-742, Korea
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155
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Twomey C, Wattam SL, Pillai MR, Rapley J, Baxter JE, Fry AM. Nek2B stimulates zygotic centrosome assembly in Xenopus laevis in a kinase-independent manner. Dev Biol 2004; 265:384-98. [PMID: 14732400 DOI: 10.1016/j.ydbio.2003.10.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Pronuclear migration and formation of the first mitotic spindle depend upon assembly of a functional zygotic centrosome. For most animals, this involves both paternal and maternal contributions as sperm basal bodies are converted into centrosomes competent for microtubule nucleation through recruitment of egg proteins. Nek2B is a vertebrate NIMA-related protein kinase required for centrosome assembly, as its depletion from egg extracts delays microtubule aster formation from sperm basal bodies. Using Xenopus as a model system, we now show that protein expression of Nek2B begins during mid-oogenesis and increases further upon oocyte maturation. This is regulated, at least in part, at the level of protein translation. Nek2B protein is weakly phosphorylated in mitotic egg extracts but its recruitment to the sperm basal body, which occurs independently of its kinase activity, stimulates its phosphorylation, possibly through sequestration from a phosphatase present in mitotic egg cytoplasm. Importantly, although Nek2B is not required to organize acentrosomal microtubule asters, we show that addition of either active or kinase-dead recombinant Nek2B can restore centrosome assembly in a dose-dependent manner to a depleted extract. These results support a model in which maternal Nek2B acts to promote assembly of a functional zygotic centrosome in a kinase-independent manner.
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Affiliation(s)
- Ciara Twomey
- Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
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156
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Di Agostino S, Fedele M, Chieffi P, Fusco A, Rossi P, Geremia R, Sette C. Phosphorylation of high-mobility group protein A2 by Nek2 kinase during the first meiotic division in mouse spermatocytes. Mol Biol Cell 2003; 15:1224-32. [PMID: 14668482 PMCID: PMC363112 DOI: 10.1091/mbc.e03-09-0638] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mitogen-activated protein kinase (MAPK) pathway is required for maintaining the chromatin condensed during the two meiotic divisions and to avoid a second round of DNA duplication. However, molecular targets of the MAPK pathway on chromatin have not yet been identified. Here, we show that the architectural chromatin protein HMGA2 is highly expressed in male meiotic cells. Furthermore, Nek2, a serine-threonine kinase activated by the MAPK pathway in mouse pachytene spermatocytes, directly interacts with HMGA2 in vitro and in mouse spermatocytes. The interaction does not depend on the activity of Nek2 and seems constitutive. On progression from pachytene to metaphase, Nek2 is activated and HMGA2 is phosphorylated in an MAPK-dependent manner. We also show that Nek2 phosphorylates in vitro HMGA2 and that this phosphorylation decreases the affinity of HMGA2 for DNA and might favor its release from the chromatin. Indeed, we find that most HMGA2 associates with chromatin in mouse pachytene spermatocytes, whereas it is excluded from the chromatin upon the G2/M progression. Because hmga2-/- mice are sterile and show a dramatic impairment of spermatogenesis, it is possible that the functional interaction between HMGA2 and Nek2 plays a crucial role in the correct process of chromatin condensation in meiosis.
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Affiliation(s)
- Silvia Di Agostino
- Dipartimento di Sanità Pubblica e Biologia Cellulare, University of Rome "Tor Vergata," 00133 Rome, Italy
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157
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Belham C, Roig J, Caldwell JA, Aoyama Y, Kemp BE, Comb M, Avruch J. A mitotic cascade of NIMA family kinases. Nercc1/Nek9 activates the Nek6 and Nek7 kinases. J Biol Chem 2003; 278:34897-909. [PMID: 12840024 DOI: 10.1074/jbc.m303663200] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Nek family of protein kinases in humans is composed of 11 members that share an amino-terminal catalytic domain related to NIMA, an Aspergillus kinase involved in the control of several aspects of mitosis, and divergent carboxyl-terminal tails of varying length. Nek6 (314AA) and Nek7 (303AA), 76% identical, have little noncatalytic sequence but bind to the carboxyl-terminal noncatalytic tail of Nercc1/Nek9, a NIMA family protein kinase that is activated in mitosis. Microinjection of anti-Nercc1 antibodies leads to spindle abnormalities and prometaphase arrest or chromosome missegregation. Herein we show that Nek6 is increased in abundance and activity during mitosis; activation requires the phosphorylation of Ser206 on the Nek6 activation loop. This phosphorylation and the activity of recombinant Nek6 is stimulated by coexpression with an activated mutant of Nercc1. Moreover, Nercc1 catalyzes the direct phosphorylation of prokaryotic recombinant Nek6 at Ser206 in vitro concomitant with 20-25-fold activation of Nek6 activity; Nercc1 activates Nek7 in vitro in a similar manner. Nercc1/Nek9 is likely to be responsible for the activation of Nek6 during mitosis and probably participates in the regulation of Nek7 as well. These findings support the conclusion that Nercc1/Nek9 and Nek6 represent a novel cascade of mitotic NIMA family protein kinases whose combined function is important for mitotic progression.
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Affiliation(s)
- Christopher Belham
- Department of Molecular Biology and Medical Services, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts 02114, USA
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158
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Faragher AJ, Fry AM. Nek2A kinase stimulates centrosome disjunction and is required for formation of bipolar mitotic spindles. Mol Biol Cell 2003; 14:2876-89. [PMID: 12857871 PMCID: PMC165683 DOI: 10.1091/mbc.e03-02-0108] [Citation(s) in RCA: 190] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Revised: 03/21/2003] [Accepted: 03/24/2003] [Indexed: 01/26/2023] Open
Abstract
Nek2A is a cell cycle-regulated kinase of the never in mitosis A (NIMA) family that is highly enriched at the centrosome. One model for Nek2A function proposes that it regulates cohesion between the mother and daughter centriole through phosphorylation of C-Nap1, a large coiled-coil protein that localizes to centriolar ends. Phosphorylation of C-Nap1 at the G2/M transition may trigger its displacement from centrioles, promoting their separation and subsequent bipolar spindle formation. To test this model, we generated tetracycline-inducible cell lines overexpressing wild-type and kinase-dead versions of Nek2A. Live cell imaging revealed that active Nek2A stimulates the sustained splitting of interphase centrioles indicative of loss of cohesion. However, this splitting is accompanied by only a partial reduction in centriolar C-Nap1. Strikingly, induction of kinase-dead Nek2A led to formation of monopolar spindles with unseparated spindle poles that lack C-Nap1. Furthermore, kinase-dead Nek2A interfered with chromosome segregation and cytokinesis and led to an overall change in the DNA content of the cell population. These results provide the first direct evidence in human cells that Nek2A function is required for the correct execution of mitosis, most likely through promotion of centrosome disjunction. However, they suggest that loss of centriole cohesion and C-Nap1 displacement may be distinct mitotic events.
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Affiliation(s)
- Alison J Faragher
- Department of Biochemistry, University of Leicester, Leicester LE1 7RH, United Kingdom
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159
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Abstract
The kidney can be thought of as the pairing of two tubes: an epithelial tube (the nephron), carrying filtered blood and engaged in ion and water transport; and endothelial tubes (the blood vessels), delivering blood and carrying away recovered solute. The development of the nephron presents several interesting questions. How does an epithelial tube form and how is it patterned into functionally distinct components and segments? What guides the interaction between the vasculature and kidney epithelia? How are epithelial cell shape and lumen diameter maintained, and what goes wrong when kidney tubules balloon into cysts? Here, I outline the progress that has been made in answering these questions using the zebrafish pronephros as a simple, accessible model of nephron development.
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Affiliation(s)
- Iain Drummond
- Department of Medicine, Harvard Medical School and Renal Unit, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129, USA.
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160
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O'Connell MJ, Krien MJE, Hunter T. Never say never. The NIMA-related protein kinases in mitotic control. Trends Cell Biol 2003; 13:221-8. [PMID: 12742165 DOI: 10.1016/s0962-8924(03)00056-4] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Mitosis sees a massive reorganization of cellular architecture. The microtubule cytoskeleton is reorganized to form a bipolar spindle between duplicated microtubule organizing centers, the chromosomes are condensed, attached to the spindle at their kinetochores, and, through the action of multiple molecular motors, the chromosomes are segregated into two daughter cells. Mitosis also sees a substantial wave of protein phosphorylation, controlling signaling events that coordinate mitotic processes and ensure accurate chromosome segregation. The key switch for the onset of mitosis is the archetypal cyclin-dependent kinase, Cdc2. Under the direction of Cdc2 is an executive of protein serine/threonine kinases that fall into three families: the Polo kinases, Aurora kinases and the NIMA-related kinases (Nrk). The latter family has proven the most enigmatic in function, although recent advances from several sources are beginning to reveal a common functional theme.
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Affiliation(s)
- Matthew J O'Connell
- Derald H. Ruttenberg Cancer Center, Mt Sinai School of Medicine, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA.
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161
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de Vos S, Hofmann WK, Grogan TM, Krug U, Schrage M, Miller TP, Braun JG, Wachsman W, Koeffler HP, Said JW. Gene expression profile of serial samples of transformed B-cell lymphomas. J Transl Med 2003; 83:271-85. [PMID: 12594241 DOI: 10.1097/01.lab.0000053913.85892.e9] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Follicular lymphoma (FL) is characterized by a continuous rate of relapse and transformation to a high-grade lymphoma, usually diffuse large B-cell lymphoma (DLBCL), associated with a dismal prognosis and a poor response to conventional chemotherapy. The progression of indolent to aggressive FL is accompanied by the successive accumulation of recurrent chromosomal defects, but the resultant alterations of gene expression are largely unknown. To expand the understanding of the pathogenesis of FL transformation, we initially performed oligonucleotide microarray analyses using Affymetrix HuFL chips on five cases with matched snap-frozen lymph nodes before and after transformation. Expression data were analyzed using the Affymetrix Microarray Suite 4.0 and Genespring 4.0. Thirty-six genes with increased expression and 66 genes with decreased expression associated with transformation were identified and functionally classified. The expression of differentially expressed genes was confirmed by real-time quantitative RT-PCR (QRT-PCR) using a total of seven matched pairs and an additional five FL and five unrelated DLBCL. In addition, selected genes were further analyzed by QRT-PCR or immunohistochemistry using a large, unrelated series of FL (grades 1 to 3) as well as transformed and de novo DLBCL (total of 51 samples). The microarray results correlated with the protein expression data obtained from samples at the time of initial diagnosis and transformation. Furthermore, the expression of 25 candidate genes was evaluated by QRT-PCR with a 78% confirmation rate. Some of the identified genes, such as nucleobindin, interferon regulatory factor 4, and tissue inhibitor of metalloproteinases 1, are already known to be associated with high-grade non-Hodgkin's lymphoma. Novel candidate genes with confirmed increased and decreased expression in transformed DLBCL include ABL2 and NEK2, and PDCD1 and VDUP1, respectively. In summary, this study shows that transformation of FL to DLBCL is associated with a distinct set of differentially expressed genes of potential functional importance.
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MESH Headings
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/pathology
- DNA Fingerprinting
- DNA Primers/chemistry
- DNA, Neoplasm/analysis
- Gene Expression Profiling/methods
- Genetic Markers
- Humans
- Lymph Nodes/metabolism
- Lymph Nodes/pathology
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/metabolism
- Lymphoma, B-Cell/pathology
- Lymphoma, Follicular/genetics
- Lymphoma, Follicular/metabolism
- Lymphoma, Follicular/pathology
- Oligonucleotide Array Sequence Analysis
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- Sven de Vos
- Division of Hematology/Oncology, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, California 90095, USA.
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