1
|
Chen H, Li YX, Wong RS, Esseltine JL, Bai D. Genetically engineered human embryonic kidney cells as a novel vehicle for dual patch clamp study of human gap junction channels. Biochem J 2024; 481:741-758. [PMID: 38752978 DOI: 10.1042/bcj20240016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 04/29/2024] [Accepted: 05/16/2024] [Indexed: 06/11/2024]
Abstract
Mutations in more than half of human connexin genes encoding gap junction (GJ) subunits have been linked to inherited human diseases. Functional studies of human GJ channels are essential for revealing mechanistic insights into the etiology of disease-linked connexin mutants. However, the commonly used Xenopus oocytes, N2A, HeLa, and other model cells for recombinant expression of human connexins have different and significant limitations. Here we developed a human cell line (HEK293) with each of the endogenous connexins (Cx43 and Cx45) knocked out using the CRISPR-Cas9 system. Double knockout HEK293 cells showed no background GJ coupling, were easily transfected with several human connexin genes (such as those encoding Cx46, Cx50, Cx37, Cx45, Cx26, and Cx36) which successfully formed functional GJs and were readily accessible for dual patch clamp analysis. Single knockout Cx43 or Cx45 HEK cell lines could also be used to characterize human GJ channels formed by Cx45 or Cx43, respectively, with an expression level suitable for studying macroscopic and single channel GJ channel properties. A cardiac arrhythmia linked Cx45 mutant R184G failed to form functional GJs in DKO HEK293 cells with impaired localizations. These genetically engineered HEK293 cells are well suited for patch clamp study of human GJ channels.
Collapse
Affiliation(s)
- Honghong Chen
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Yi X Li
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Robert S Wong
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| | - Jessica L Esseltine
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada A1B 3V6
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1
| |
Collapse
|
2
|
Santoni M, Meneau F, Sekhsoukh N, Castella S, Le T, Miot M, Daldello EM. Unraveling the interplay between PKA inhibition and Cdk1 activation during oocyte meiotic maturation. Cell Rep 2024; 43:113782. [PMID: 38358892 DOI: 10.1016/j.celrep.2024.113782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 12/19/2023] [Accepted: 01/25/2024] [Indexed: 02/17/2024] Open
Abstract
Oocytes are arrested in prophase I. In vertebrates, meiotic resumption is triggered by hormonal stimulation that results in cAMP-dependent protein kinase (PKA) downregulation leading to Cdk1 activation. Yet the pathways connecting PKA to Cdk1 remain unclear. Here, we identify molecular events triggered by PKA downregulation occurring upstream of Cdk1 activation. We describe a two-step regulation controlling cyclin B1 and Mos accumulation, which depends on both translation and stabilization. Cyclin B1 accumulation is triggered by PKA inhibition upstream of Cdk1 activation, while its translation requires Cdk1 activity. Conversely, Mos translation initiates in response to the hormone, but the protein accumulates only downstream of Cdk1. Furthermore, two successive translation waves take place, the first controlled by PKA inhibition and the second by Cdk1 activation. Notably, Arpp19, an essential PKA effector, does not regulate the early PKA-dependent events. This study elucidates how PKA downregulation orchestrates multiple pathways that converge toward Cdk1 activation and induce the oocyte G2/M transition.
Collapse
Affiliation(s)
- Martina Santoni
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Ferdinand Meneau
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Nabil Sekhsoukh
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Sandrine Castella
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Tran Le
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Marika Miot
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France
| | - Enrico Maria Daldello
- Sorbonne Université-CNRS, Laboratoire de Biologie du Développement Institut de Biologie Paris Seine, LBD-IBPS, 75005 Paris, France.
| |
Collapse
|
3
|
El Dika M, Dudka D, Kloc M, Kubiak JZ. CDC6 as a Key Inhibitory Regulator of CDK1 Activation Dynamics and the Timing of Mitotic Entry and Progression. BIOLOGY 2023; 12:855. [PMID: 37372141 DOI: 10.3390/biology12060855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 06/08/2023] [Accepted: 06/09/2023] [Indexed: 06/29/2023]
Abstract
Timely mitosis is critically important for early embryo development. It is regulated by the activity of the conserved protein kinase CDK1. The dynamics of CDK1 activation must be precisely controlled to assure physiologic and timely entry into mitosis. Recently, a known S-phase regulator CDC6 emerged as a key player in mitotic CDK1 activation cascade in early embryonic divisions, operating together with Xic1 as a CDK1 inhibitor upstream of the Aurora A and PLK1, both CDK1 activators. Herein, we review the molecular mechanisms that underlie the control of mitotic timing, with special emphasis on how CDC6/Xic1 function impacts CDK1 regulatory network in the Xenopus system. We focus on the presence of two independent mechanisms inhibiting the dynamics of CDK1 activation, namely Wee1/Myt1- and CDC6/Xic1-dependent, and how they cooperate with CDK1-activating mechanisms. As a result, we propose a comprehensive model integrating CDC6/Xic1-dependent inhibition into the CDK1-activation cascade. The physiological dynamics of CDK1 activation appear to be controlled by the system of multiple inhibitors and activators, and their integrated modulation ensures concomitantly both the robustness and certain flexibility of the control of this process. Identification of multiple activators and inhibitors of CDK1 upon M-phase entry allows for a better understanding of why cells divide at a specific time and how the pathways involved in the timely regulation of cell division are all integrated to precisely tune the control of mitotic events.
Collapse
Affiliation(s)
- Mohammed El Dika
- Department of Biochemistry, Larner College of Medicine, UVM Cancer Center, University of Vermont, Burlington, VT 05405, USA
| | - Damian Dudka
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Malgorzata Kloc
- The Houston Methodist Research Institute, Transplant Immunology, Houston, TX 77030, USA
- Department of Surgery, The Houston Methodist Hospital, Houston, TX 77030, USA
- Department of Genetics, MD Anderson Cancer Center, The University of Texas, Houston, TX 77030, USA
| | - Jacek Z Kubiak
- Laboratory of Molecular Oncology and Innovative Therapies, Military Institute of Medicine-National Research Institute (WIM-PIB), Szaserow 128, 04-141 Warsaw, Poland
- Dynamics and Mechanics of Epithelia Group, Faculty of Medicine, Institute of Genetics and Development of Rennes, University of Rennes, CNRS, UMR 6290, 35043 Rennes, France
| |
Collapse
|
4
|
Lemonnier T, Dupré A, Jessus C. The G2-to-M transition from a phosphatase perspective: a new vision of the meiotic division. Cell Div 2020; 15:9. [PMID: 32508972 PMCID: PMC7249327 DOI: 10.1186/s13008-020-00065-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 05/12/2020] [Indexed: 12/15/2022] Open
Abstract
Cell division is orchestrated by the phosphorylation and dephosphorylation of thousands of proteins. These post-translational modifications underlie the molecular cascades converging to the activation of the universal mitotic kinase, Cdk1, and entry into cell division. They also govern the structural events that sustain the mechanics of cell division. While the role of protein kinases in mitosis has been well documented by decades of investigations, little was known regarding the control of protein phosphatases until the recent years. However, the regulation of phosphatase activities is as essential as kinases in controlling the activation of Cdk1 to enter M-phase. The regulation and the function of phosphatases result from post-translational modifications but also from the combinatorial association between conserved catalytic subunits and regulatory subunits that drive their substrate specificity, their cellular localization and their activity. It now appears that sequential dephosphorylations orchestrated by a network of phosphatase activities trigger Cdk1 activation and then order the structural events necessary for the timely execution of cell division. This review discusses a series of recent works describing the important roles played by protein phosphatases for the proper regulation of meiotic division. Many breakthroughs in the field of cell cycle research came from studies on oocyte meiotic divisions. Indeed, the meiotic division shares most of the molecular regulators with mitosis. The natural arrests of oocytes in G2 and in M-phase, the giant size of these cells, the variety of model species allowing either biochemical or imaging as well as genetics approaches explain why the process of meiosis has served as an historical model to decipher signalling pathways involved in the G2-to-M transition. The review especially highlights how the phosphatase PP2A-B55δ critically orchestrates the timing of meiosis resumption in amphibian oocytes. By opposing the kinase PKA, PP2A-B55δ controls the release of the G2 arrest through the dephosphorylation of their substrate, Arpp19. Few hours later, the inhibition of PP2A-B55δ by Arpp19 releases its opposing kinase, Cdk1, and triggers M-phase. In coordination with a variety of phosphatases and kinases, the PP2A-B55δ/Arpp19 duo therefore emerges as the key effector of the G2-to-M transition.
Collapse
Affiliation(s)
- Tom Lemonnier
- Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine, LBD-IBPS, Sorbonne Université, CNRS, 75005 Paris, France
| | - Aude Dupré
- Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine, LBD-IBPS, Sorbonne Université, CNRS, 75005 Paris, France
| | - Catherine Jessus
- Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine, LBD-IBPS, Sorbonne Université, CNRS, 75005 Paris, France
| |
Collapse
|
5
|
Wang H, Choe MH, Lee IW, Namgoong S, Kim JS, Kim NH, Oh JS. CIP2A acts as a scaffold for CEP192-mediated microtubule organizing center assembly by recruiting Plk1 and aurora A during meiotic maturation. Development 2017; 144:3829-3839. [PMID: 28935709 DOI: 10.1242/dev.158584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 09/06/2017] [Indexed: 12/16/2023]
Abstract
In somatic cells spindle microtubules are nucleated from centrosomes that act as major microtubule organizing centers (MTOCs), whereas oocytes form meiotic spindles by assembling multiple acentriolar MTOCs without canonical centrosomes. Aurora A and Plk1 are required for these events, but the underlying mechanisms remain largely unknown. Here we show that CIP2A regulates MTOC organization by recruiting aurora A and Plk1 at spindle poles during meiotic maturation. CIP2A colocalized with pericentrin at spindle poles with a few distinct cytoplasmic foci. Although CIP2A has been identified as an endogenous inhibitor of protein phosphatase 2A (PP2A), overexpression of CIP2A had no effect on meiotic maturation. Depletion of CIP2A perturbed normal spindle organization and chromosome alignment by impairing MTOC organization. Importantly, CIP2A was reciprocally associated with CEP192, promoting recruitment of aurora A and Plk1 at MTOCs. CIP2A was phosphorylated by Plk1 at S904, which targets CIP2A to MTOCs and facilitates MTOC organization with CEP192. Our results suggest that CIP2A acts as a scaffold for CEP192-mediated MTOC assembly by recruiting Plk1 and aurora A during meiotic maturation in mouse oocytes.
Collapse
Affiliation(s)
- HaiYang Wang
- Department of Animal Sciences, Chungbuk National University, Cheongju 28644, Korea
| | - Min Ho Choe
- Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 01812, Korea
- Department of Life Sciences and Biotechnology, College of Life Science and Biotechnology, Korea University, Seoul 02841, Korea
| | - In-Won Lee
- Department of Animal Sciences, Chungbuk National University, Cheongju 28644, Korea
| | - Suk Namgoong
- Department of Animal Sciences, Chungbuk National University, Cheongju 28644, Korea
| | - Jae-Sung Kim
- Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, Seoul 01812, Korea
| | - Nam-Hyung Kim
- Department of Animal Sciences, Chungbuk National University, Cheongju 28644, Korea
| | - Jeong Su Oh
- Department of Genetic Engineering, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon 16419, Korea
| |
Collapse
|
6
|
Kang Q, Srividhya J, Ipe J, Pomerening JR. Evidence toward a dual phosphatase mechanism that restricts Aurora A (Thr-295) phosphorylation during the early embryonic cell cycle. J Biol Chem 2014; 289:17480-96. [PMID: 24825897 DOI: 10.1074/jbc.m113.527622] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The mitotic kinase Aurora A (AurA) is regulated by a complex network of factors that includes co-activator binding, autophosphorylation, and dephosphorylation. Dephosphorylation of AurA by PP2A (human, Ser-51; Xenopus, Ser-53) destabilizes the protein, whereas mitotic dephosphorylation of its T-loop (human, Thr-288; Xenopus, Thr-295) by PP6 represses AurA activity. However, AurA(Thr-295) phosphorylation is restricted throughout the early embryonic cell cycle, not just during M-phase, and how Thr-295 is kept dephosphorylated during interphase and whether or not this mechanism impacts the cell cycle oscillator were unknown. Titration of okadaic acid (OA) or fostriecin into Xenopus early embryonic extract revealed that phosphatase activity other than PP1 continuously suppresses AurA(Thr-295) phosphorylation during the early embryonic cell cycle. Unexpectedly, we observed that inhibiting a phosphatase activity highly sensitive to OA caused an abnormal increase in AurA(Thr-295) phosphorylation late during interphase that corresponded with delayed cyclin-dependent kinase 1 (CDK1) activation. AurA(Thr-295) phosphorylation indeed influenced this timing, because AurA isoforms retaining an intact Thr-295 residue further delayed M-phase entry. Using mathematical modeling, we determined that one phosphatase would be insufficient to restrict AurA phosphorylation and regulate CDK1 activation, whereas a dual phosphatase topology best recapitulated our experimental observations. We propose that two phosphatases target Thr-295 of AurA to prevent premature AurA activation during interphase and that phosphorylated AurA(Thr-295) acts as a competitor substrate with a CDK1-activating phosphatase in late interphase. These results suggest a novel relationship between AurA and protein phosphatases during progression throughout the early embryonic cell cycle and shed new light on potential defects caused by AurA overexpression.
Collapse
Affiliation(s)
- Qing Kang
- From the Department of Biology, Indiana University, Bloomington, Indiana 47405-7003
| | - Jeyaraman Srividhya
- From the Department of Biology, Indiana University, Bloomington, Indiana 47405-7003
| | - Joseph Ipe
- From the Department of Biology, Indiana University, Bloomington, Indiana 47405-7003
| | - Joseph R Pomerening
- From the Department of Biology, Indiana University, Bloomington, Indiana 47405-7003
| |
Collapse
|
7
|
Domingo-Sananes MR, Kapuy O, Hunt T, Novak B. Switches and latches: a biochemical tug-of-war between the kinases and phosphatases that control mitosis. Philos Trans R Soc Lond B Biol Sci 2012; 366:3584-94. [PMID: 22084385 DOI: 10.1098/rstb.2011.0087] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of the cyclin-dependent kinase (Cdk1) cyclin B (CycB) complex (Cdk1:CycB) in mitosis brings about a remarkable extent of protein phosphorylation. Cdk1:CycB activation is switch-like, controlled by two auto-amplification loops--Cdk1:CycB activates its activating phosphatase, Cdc25, and inhibits its inhibiting kinase, Wee1. Recent experimental evidence suggests that parallel to Cdk1:CycB activation during mitosis, there is inhibition of its counteracting phosphatase activity. We argue that the downregulation of the phosphatase is not just a simple latch that suppresses futile cycles of phosphorylation/dephosphorylation during mitosis. Instead, we propose that phosphatase regulation creates coherent feed-forward loops and adds extra amplification loops to the Cdk1:CycB regulatory network, thus forming an integral part of the mitotic switch. These network motifs further strengthen the bistable characteristic of the mitotic switch, which is based on the antagonistic interaction of two groups of proteins: M-phase promoting factors (Cdk1:CycB, Cdc25, Greatwall and Endosulfine/Arpp19) and interphase promoting factors (Wee1, PP2A-B55 and a Greatwall counteracting phosphatase, probably PP1). The bistable character of the switch implies the existence of a CycB threshold for entry into mitosis. The end of G2 phase is determined by the point where CycB level crosses the CycB threshold for Cdk1 activation.
Collapse
Affiliation(s)
- Maria Rosa Domingo-Sananes
- Department of Biochemistry, Oxford Centre for Integrative Systems Biology, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | | | | | | |
Collapse
|
8
|
Krasinska L, Domingo-Sananes MR, Kapuy O, Parisis N, Harker B, Moorhead G, Rossignol M, Novák B, Fisher D. Protein phosphatase 2A controls the order and dynamics of cell-cycle transitions. Mol Cell 2011; 44:437-50. [PMID: 22055189 DOI: 10.1016/j.molcel.2011.10.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 03/01/2011] [Accepted: 08/12/2011] [Indexed: 11/24/2022]
Abstract
Bistability of the Cdk1-Wee1-Cdc25 mitotic control network underlies the switch-like transitions between interphase and mitosis. Here, we show by mathematical modeling and experiments in Xenopus egg extracts that protein phosphatase 2A (PP2A), which can dephosphorylate Cdk1 substrates, is essential for this bistability. PP2A inhibition in early interphase abolishes the switch-like response of the system to Cdk1 activity, promoting mitotic onset even with very low levels of Cyclin, Cdk1, and Cdc25, while simultaneously inhibiting DNA replication. Furthermore, even if replication has already initiated, it cannot continue in mitosis. Exclusivity of S and M phases does not depend on bistability only, since partial PP2A inhibition prevents replication without inducing mitotic onset. In these conditions, interphase-level mitotic kinases inhibit Cyclin E-Cdk2 chromatin loading, blocking initiation complex formation. Therefore, by counteracting both Cdk1 activation and activity of mitotic kinases, PP2A ensures robust separation of S phase and mitosis and dynamic transitions between the two states.
Collapse
Affiliation(s)
- Liliana Krasinska
- Institute of Molecular Genetics, CNRS, UMR5535, University of Montpellier I and II, 34293 Montpellier, France
| | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Gotoh T, Villa LM, Capelluto DGS, Finkielstein CV. Regulatory pathways coordinating cell cycle progression in early Xenopus development. Results Probl Cell Differ 2011; 53:171-99. [PMID: 21630146 DOI: 10.1007/978-3-642-19065-0_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The African clawed frog, Xenopus laevis, is used extensively as a model organism for studying both cell development and cell cycle regulation. For over 20 years now, this model organism has contributed to answering fundamental questions concerning the mechanisms that underlie cell cycle transitions--the cellular components that synthesize, modify, repair, and degrade nucleic acids and proteins, the signaling pathways that allow cells to communicate, and the regulatory pathways that lead to selective expression of subsets of genes. In addition, the remarkable simplicity of the Xenopus early cell cycle allows for tractable manipulation and dissection of the basic components driving each transition. In this organism, early cell divisions are characterized by rapid cycles alternating phases of DNA synthesis and division. The post-blastula stages incorporate gap phases, lengthening progression, and allowing more time for DNA repair. Various cyclin/Cdk complexes are differentially expressed during the early cycles with orderly progression being driven by both the combined action of cyclin synthesis and degradation and the appropriate selection of specific substrates by their Cdk components. Like other multicellular organisms, chief developmental events in early Xenopus embryogenesis coincide with profound remodeling of the cell cycle, suggesting that cell proliferation and differentiation events are linked and coordinated through crosstalk mechanisms acting on signaling pathways involving the expression of cell cycle control genes.
Collapse
Affiliation(s)
- Tetsuya Gotoh
- Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, 1981 Kraft Drive, Blacksburg, VA 24061, USA
| | | | | | | |
Collapse
|
10
|
Yamamoto TM, Blake-Hodek K, Williams BC, Lewellyn AL, Goldberg ML, Maller JL. Regulation of Greatwall kinase during Xenopus oocyte maturation. Mol Biol Cell 2011; 22:2157-64. [PMID: 21551066 PMCID: PMC3128519 DOI: 10.1091/mbc.e11-01-0008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Greatwall kinase is required for M phase maintenance by inhibiting PP2A. Gwl associates with PP2A in G2 oocytes, but the complex dissociates during M phase (meiosis I). Mutating Lys71 to Met (K71M) generates gain-of-function Gwl kinase activity toward endosulfinethat is sufficient to induce oocyte maturation in the absence of progesterone. Greatwall kinase has been identified as a key element in M phase initiation and maintenance in Drosophila, Xenopus oocytes/eggs, and mammalian cells. In M phase, Greatwall phosphorylates endosulfine and related proteins that bind to and inhibit protein phosphatase 2A/B55, the principal phosphatase for Cdk-phosphorylated substrates. We show that Greatwall binds active PP2A/B55 in G2 phase oocytes but dissociates from it when progesterone-treated oocytes reach M phase. This dissociation does not require Greatwall kinase activity or phosphorylation at T748 in the presumptive T loop of the kinase. A mutant K71M Greatwall, also known as Scant in Drosophila, induces M phase in the absence of progesterone when expressed in oocytes, despite its reduced stability and elevated degradation by the proteasome. M phase induction by Scant Greatwall requires protein synthesis but is not associated with altered binding or release of PP2A/B55 as compared to wild-type Greatwall. However, in vitro studies with Greatwall proteins purified from interphase cells indicate that Scant, but not wild-type Greatwall, has low but detectable activity against endosulfine. These results demonstrate progesterone-dependent regulation of the PP2A/B55–Greatwall interaction during oocyte maturation and suggest that the cognate Scant Greatwall mutation has sufficient constitutive kinase activity to promote M phase in Xenopus oocytes.
Collapse
Affiliation(s)
- Tomomi M Yamamoto
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | | | | | | | | | | |
Collapse
|
11
|
Haccard O, Jessus C. Greatwall kinase, ARPP-19 and protein phosphatase 2A: shifting the mitosis paradigm. Results Probl Cell Differ 2011; 53:219-234. [PMID: 21630148 DOI: 10.1007/978-3-642-19065-0_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Control of entry into mitosis has long been seen in terms of an explosive activation of cyclin-dependent kinase 1, the mitotic driver ensuring the phosphorylation of hundreds of proteins required for cell division. However, if these phosphorylations are maintained during M-phase, they must be removed when cells exit mitosis. It has been surmised that an "antimitotic" phosphatase must be inhibited to allow mitosis entry and activated for returning to interphase. This chapter discusses a series of recent works conducted on Xenopus egg extracts that provide the answers regarding the identity and the regulation of such a phosphatase. PP2A-B55δ is the major phosphatase controlling exit from mitosis; it is negatively regulated by the kinase Greatwall that phosphorylates the small protein ARPP-19 and converts it into a potent PP2A inhibitor. These findings provide a new element of paramount importance in the control of mitosis.
Collapse
Affiliation(s)
- Olivier Haccard
- UMR-CNRS 7622 Biologie du Développement, Université Paris 6, 9 quai Saint-Bernard, 75005 Paris, France
| | | |
Collapse
|
12
|
Greatwall kinase protects mitotic phosphosites from barbarian phosphatases. Proc Natl Acad Sci U S A 2010; 107:12409-10. [PMID: 20615940 DOI: 10.1073/pnas.1006046107] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
13
|
Takemoto A, Maeshima K, Ikehara T, Yamaguchi K, Murayama A, Imamura S, Imamoto N, Yokoyama S, Hirano T, Watanabe Y, Hanaoka F, Yanagisawa J, Kimura K. The chromosomal association of condensin II is regulated by a noncatalytic function of PP2A. Nat Struct Mol Biol 2009; 16:1302-8. [PMID: 19915589 DOI: 10.1038/nsmb.1708] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 09/22/2009] [Indexed: 01/08/2023]
Abstract
Mitotic chromosomal assembly in vertebrates is regulated by condensin I and condensin II, which work cooperatively but have different chromosomal localization profiles and make distinct mechanistic contributions to this process. We show here that protein phosphatase 2A (PP2A), which interacts with condensin II but not condensin I, plays an essential role in targeting condensin II to chromosomes. Unexpectedly, our data indicate that PP2A acts as a recruiter protein rather than a catalytic enzyme to target condensin II to chromosomes. This recruiting activity of PP2A was inhibited by okadaic acid, but not by fostriecin, even though both molecules strongly inhibited the catalytic activity of PP2A. Additionally, we found that the chromokinesin KIF4a is also targeted to chromosomes via the noncatalytic activity of PP2A. Thus, our studies reveal a previously unknown contribution of PP2A to chromosome assembly.
Collapse
Affiliation(s)
- Ai Takemoto
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba Science City, Ibaraki, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Castilho PV, Williams BC, Mochida S, Zhao Y, Goldberg ML. The M phase kinase Greatwall (Gwl) promotes inactivation of PP2A/B55delta, a phosphatase directed against CDK phosphosites. Mol Biol Cell 2009; 20:4777-89. [PMID: 19793917 DOI: 10.1091/mbc.e09-07-0643] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We have previously shown that Greatwall kinase (Gwl) is required for M phase entry and maintenance in Xenopus egg extracts. Here, we demonstrate that Gwl plays a crucial role in a novel biochemical pathway that inactivates, specifically during M phase, "antimitotic" phosphatases directed against phosphorylations catalyzed by cyclin-dependent kinases (CDKs). A major component of this phosphatase activity is heterotrimeric PP2A containing the B55delta regulatory subunit. Gwl is activated during M phase by Cdk1/cyclin B (MPF), but once activated, Gwl promotes PP2A/B55delta inhibition with no further requirement for MPF. In the absence of Gwl, PP2A/B55delta remains active even when MPF levels are high. The removal of PP2A/B55delta corrects the inability of Gwl-depleted extracts to enter M phase. These findings support the hypothesis that M phase requires not only high levels of MPF function, but also the suppression, through a Gwl-dependent mechanism, of phosphatase(s) that would otherwise remove MPF-driven phosphorylations.
Collapse
Affiliation(s)
- Priscila V Castilho
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | | | | | | | | |
Collapse
|
15
|
Lin X, Liu S, Luo X, Ma X, Guo L, Li L, Li Z, Tao Y, Cao Y. EBV-encoded LMP1 regulates Op18/stathmin signaling pathway by cdc2 mediation in nasopharyngeal carcinoma cells. Int J Cancer 2009; 124:1020-7. [PMID: 19048596 DOI: 10.1002/ijc.23767] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Oncoprotein 18/stathmin (Op18/stathmin) plays a crucial role in maintaining cell biological characteristics by regulating microtubule dynamics, especially entry into mitosis; phosphorylated Op18/stathmin promotes microtubule polymerization to form the mitotic spindle, which is essential for chromosome segregation and cell division. Cdc2 is a critical kinase in starting M phase events in cell-cycle progression and is a positive regulator of the cell cycle. Latent membrane protein 1 (LMP1) is an Epstein-Barr virus (EBV)-encoded oncogenic protein that is able to induce carcinogenesis via various signaling pathways. This study focused on regulation by LMP1 of Op18/stathmin signaling in nasopharyngeal carcinoma (NPC) cells and showed that LMP1 regulates Op18/stathmin signaling through cdc2 mediation, LMP1 upregulates cdc2 kinase activity, and Op18/stathmin phosphorylation promotes the interaction of cdc2 with Op18/stathmin and microtubule polymerization during mitosis, and inhibition of LMP1 expression attenuates the interaction of cdc2 and Op18/stathmin and promotes microtubule depolymerization. These results reveal a new pathway via which LMP1 regulates Op18/stathmin signaling by cdc2 mediation; this new signaling pathway not only perfects the LMP1 regulation network but also elucidates the molecular mechanism of LMP1 that leads to carcinogenesis.
Collapse
Affiliation(s)
- Xuechi Lin
- Cancer Research Institute, Xiangya School of Medicine, Central South University, Hunan, People's Republic of China
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Nishimura Y, Endo T, Kano K, Naito K. Porcine Aurora A accelerates Cyclin B and Mos synthesis and promotes meiotic resumption of porcine oocytes. Anim Reprod Sci 2008; 113:114-24. [PMID: 18614302 DOI: 10.1016/j.anireprosci.2008.05.074] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Revised: 03/21/2008] [Accepted: 05/26/2008] [Indexed: 11/19/2022]
Abstract
Full-grown oocytes arrested at germinal vesicle stage contain many dormant maternal mRNAs, and Aurora A has been reported to play a key role for the translation of these maternal mRNAs in Xenopus oocytes. Although the presence of Aurora A has been reported in mammals, the functions of Aurora A on the protein synthesis and the meiotic resumption have never been elucidated in mammalian oocytes. In the present study, the effects of porcine Aurora A on meiotic resumption of porcine oocytes were examined. At first, we cloned porcine Aurora A from total RNA of immature porcine oocytes by RT-PCR and obtained full-length cDNA that was 77%, 86% and 54% homologous with mouse, human and Xenopus Aurora A, respectively. The Aurora A mRNA and large amounts of protein were present throughout maturation period in porcine oocytes. The overexpression of porcine Aurora A by the mRNA injection into immature porcine oocytes had no effects on Cyclin B synthesis and meiotic resumption. Therefore we constructed a mutated Aurora A (AA-Aurora A), which was replaced the expecting inhibitory phosphorylation sites, serines 283 and 284, to non-phosphorylatable alanines. The oocytes expressed AA-Aurora A were accelerated their Cyclin B synthesis and Rsk phosphorylation, an indicator of Mos synthesis, then their meiotic resumption was promoted significantly. These results suggest for the first time in mammalian oocytes that mammalian Aurora A stimulates the protein synthesis and promotes the meiotic resumption. In addition, we identified the inhibitory phosphorylation sites of porcine Aurora A, and indicate the presence of phosphorylation-dependent regulation mechanisms in mammalian Aurora A.
Collapse
Affiliation(s)
- Yukio Nishimura
- Department of Animal Resource Sciences, Graduate School of Agricultural Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | | | | | | |
Collapse
|
17
|
Dehennaut V, Slomianny MC, Page A, Vercoutter-Edouart AS, Jessus C, Michalski JC, Vilain JP, Bodart JF, Lefebvre T. Identification of structural and functional O-linked N-acetylglucosamine-bearing proteins in Xenopus laevis oocyte. Mol Cell Proteomics 2008; 7:2229-45. [PMID: 18617508 DOI: 10.1074/mcp.m700494-mcp200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
O-Linked N-acetylglucosaminylation (O-GlcNAcylation) (or O-linked N-acetylglucosamine (O-GlcNAc)) is an abundant and reversible glycosylation type found within the cytosolic and the nuclear compartments. We have described previously the sudden O-GlcNAcylation increase occurring during the Xenopus laevis oocyte G(2)/M transition, and we have demonstrated that the inhibition of O-GlcNAc-transferase (OGT) blocked this process, showing that the O-GlcNAcylation dynamism interferes with the cell cycle progression. In this work, we identified proteins that are O-GlcNAc-modified during the G(2)/M transition. Because of a low expression of O-GlcNAcylation in Xenopus oocyte, classical enrichment of O-GlcNAc-bearing proteins using O-GlcNAc-directed antibodies or wheat germ agglutinin lectin affinity were hard to apply, albeit these techniques allowed the identification of actin and erk2. Therefore, another strategy based on an in vitro enzymatic labeling of O-GlcNAc residues with azido-GalNAc followed by a chemical addition of a biotin alkyne probe and by enrichment of the tagged proteins on avidin beads was used. Bound proteins were analyzed by nano-LC-nano-ESI-MS/MS allowing for the identification of an average of 20 X. laevis oocyte O-GlcNAcylated proteins. In addition to actin and beta-tubulin, we identified metabolic/functional proteins such as PP2A, proliferating cell nuclear antigen, transitional endoplasmic reticulum ATPase, aldolase, lactate dehydrogenase, and ribosomal proteins. This labeling allowed for the mapping of a major O-GlcNAcylation site within the 318-324 region of beta-actin. Furthermore immunofluorescence microscopy enabled the direct visualization of O-GlcNAcylation and OGT on the meiotic spindle as well as the observation that chromosomally bound proteins were enriched in O-GlcNAc and OGT. The biological relevance of this post-translational modification both on microtubules and on chromosomes remains to be determined. However, the mapping of the O-GlcNAcylation sites will help to underline the function of this post-translational modification on each identified protein and will provide a better understanding of O-GlcNAcylation in the control of the cell cycle.
Collapse
Affiliation(s)
- Vanessa Dehennaut
- UMR-CNRS 8576, Unité de Glycobiologie Structurale et Fonctionnelle, Université des Sciences et Technologies de Lille, IFR 147, 59655 Villeneuve d'Ascq, France
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Targeted disruption of the PME-1 gene causes loss of demethylated PP2A and perinatal lethality in mice. PLoS One 2008; 3:e2486. [PMID: 18596935 PMCID: PMC2438471 DOI: 10.1371/journal.pone.0002486] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 05/13/2008] [Indexed: 11/29/2022] Open
Abstract
Background Phosphoprotein phosphatase 2A (PP2A), a major serine-threonine protein phosphatase in eukaryotes, is an oligomeric protein comprised of structural (A) and catalytic (C) subunits to which a variable regulatory subunit (B) can associate. The C subunit contains a methyl ester post-translational modification on its C-terminal leucine residue, which is removed by a specific methylesterase (PME-1). Methylesterification is thought to control the binding of different B subunits to AC dimers, but little is known about its physiological significance in vivo. Methodology/Principal Findings Here, we show that targeted disruption of the PME-1 gene causes perinatal lethality in mice, a phenotype that correlates with a virtually complete loss of the demethylated form of PP2A in the nervous system and peripheral tissues. Interestingly, PP2A catalytic activity over a peptide substrate was dramatically reduced in PME-1(−/−) tissues, which also displayed alterations in phosphoproteome content. Conclusions These findings suggest a role for the demethylated form of PP2A in maintenance of enzyme function and phosphorylation networks in vivo.
Collapse
|
19
|
Uzbekova S, Arlot-Bonnemains Y, Dupont J, Dalbiès-Tran R, Papillier P, Pennetier S, Thélie A, Perreau C, Mermillod P, Prigent C, Uzbekov R. Spatio-Temporal Expression Patterns of Aurora Kinases A, B, and C and Cytoplasmic Polyadenylation-Element-Binding Protein in Bovine Oocytes During Meiotic Maturation1. Biol Reprod 2008; 78:218-33. [PMID: 17687118 DOI: 10.1095/biolreprod.107.061036] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Maturation of immature bovine oocytes requires cytoplasmic polyadenylation and synthesis of a number of proteins involved in meiotic progression and metaphase-II arrest. Aurora serine-threonine kinases--localized in centrosomes, chromosomes, and midbody--regulate chromosome segregation and cytokinesis in somatic cells. In frog and mouse oocytes, Aurora A regulates polyadenylation-dependent translation of several mRNAs such as MOS and CCNB1, presumably by phosphorylating CPEB, and Aurora B phosphorylates histone H3 during meiosis. We analyzed the expression of three Aurora kinase genes--AURKA, AURKB, and AURKC--in bovine oocytes during meiosis by reverse transcription followed by quantitative real-time PCR and immunodetection. Aurora A was the most abundant form in oocytes, both at mRNA and protein levels. AURKA protein progressively accumulated in the oocyte cytoplasm during antral follicle growth and in vitro maturation. AURKB associated with metaphase chromosomes. AURKB, AURKC, and Thr-phosphorylated AURKA were detected at a contractile ring/midbody during the first polar body extrusion. CPEB, localized in oocyte cytoplasm, was hyperphosphorylated during prophase/metaphase-I transition. Most CPEB degraded in metaphase-II oocytes and remnants remained localized in a contractile ring. Roscovitine, U0126, and metformin inhibited meiotic divisions; they all induced a decrease of CCNB1 and phospho-MAPK3/1 levels and prevented CPEB degradation. However, only metformin depleted AURKA. The Aurora kinase inhibitor VX680 at 100 nmol/L did not inhibit meiosis but led to multinuclear oocytes due to the failure of the polar body extrusion. Thus, in bovine oocyte meiosis, massive destruction of CPEB accompanies metaphase-I/II transition, and Aurora kinases participate in regulating segregation of the chromosomes, maintenance of metaphase-II, and formation of the first polar body.
Collapse
Affiliation(s)
- Svetlana Uzbekova
- INRA, UMR85 Physiologie de Reproduction et des Comportements, CNRS, UMR6175, Université de Tours, Haras Nationaux, 37380 Nouzilly, France.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Zhao Y, Haccard O, Wang R, Yu J, Kuang J, Jessus C, Goldberg ML. Roles of Greatwall kinase in the regulation of cdc25 phosphatase. Mol Biol Cell 2008; 19:1317-27. [PMID: 18199678 DOI: 10.1091/mbc.e07-11-1099] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We previously reported that immunodepletion of Greatwall kinase prevents Xenopus egg extracts from entering or maintaining M phase due to the accumulation of inhibitory phosphorylations on Thr14 and Tyr15 of Cdc2. M phase-promoting factor (MPF) in turn activates Greatwall, implying that Greatwall participates in an MPF autoregulatory loop. We show here that activated Greatwall both accelerates the mitotic G2/M transition in cycling egg extracts and induces meiotic maturation in G2-arrested Xenopus oocytes in the absence of progesterone. Activated Greatwall can induce phosphorylations of Cdc25 in the absence of the activity of Cdc2, Plx1 (Xenopus Polo-like kinase) or mitogen-activated protein kinase, or in the presence of an activator of protein kinase A that normally blocks mitotic entry. The effects of active Greatwall mimic in many respects those associated with addition of the phosphatase inhibitor okadaic acid (OA); moreover, OA allows cycling extracts to enter M phase in the absence of Greatwall. Taken together, these findings support a model in which Greatwall negatively regulates a crucial phosphatase that inhibits Cdc25 activation and M phase induction.
Collapse
Affiliation(s)
- Yong Zhao
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853-2703, USA
| | | | | | | | | | | | | |
Collapse
|
21
|
Han J, Han L, Tiwari P, Wen Z, Zheng JQ. Spatial targeting of type II protein kinase A to filopodia mediates the regulation of growth cone guidance by cAMP. ACTA ACUST UNITED AC 2007; 176:101-11. [PMID: 17200417 PMCID: PMC2063631 DOI: 10.1083/jcb.200607128] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The second messenger cyclic adenosine monophosphate (cAMP) plays a pivotal role in axonal growth and guidance, but its downstream mechanisms remain elusive. In this study, we report that type II protein kinase A (PKA) is highly enriched in growth cone filopodia, and this spatial localization enables the coupling of cAMP signaling to its specific effectors to regulate guidance responses. Disrupting the localization of PKA to filopodia impairs cAMP-mediated growth cone attraction and prevents the switching of repulsive responses to attraction by elevated cAMP. Our data further show that PKA targets protein phosphatase-1 (PP1) through the phosphorylation of a regulatory protein inhibitor-1 (I-1) to promote growth cone attraction. Finally, we find that I-1 and PP1 mediate growth cone repulsion induced by myelin-associated glycoprotein. These findings demonstrate that the spatial localization of type II PKA to growth cone filopodia plays an important role in the regulation of growth cone motility and guidance by cAMP.
Collapse
Affiliation(s)
- Jianzhong Han
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
| | | | | | | | | |
Collapse
|
22
|
Keady BT, Kuo P, Martínez SE, Yuan L, Hake LE. MAPK interacts with XGef and is required for CPEB activation during meiosis in Xenopus oocytes. J Cell Sci 2007; 120:1093-103. [PMID: 17344432 DOI: 10.1242/jcs.03416] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Meiotic progression in Xenopus oocytes, and all other oocytes investigated, is dependent on polyadenylation-induced translation of stockpiled maternal mRNAs. Early during meiotic resumption, phosphorylation of CPE-binding protein (CPEB) is required for polyadenylation-induced translation of mRNAs encoding cell cycle regulators. Xenopus Gef (XGef), a Rho-family guanine-exchange factor, influences the activating phosphorylation of CPEB. An exchange-deficient version of XGef does not, therefore implicating Rho-family GTPase function in early meiosis. We show here that Clostridium difficile Toxin B, a Rho-family GTPase inhibitor, does not impair early CPEB phosphorylation or progression to germinal vesicle breakdown, indicating that XGef does not influence these events through activation of a Toxin-B-sensitive GTPase. Using the inhibitors U0126 for mitogen-activated protein kinase (MAPK), and ZM447439 for Aurora kinase A and Aurora kinase B, we found that MAPK is required for phosphorylation of CPEB, whereas Aurora kinases are not. Furthermore, we do not detect active Aurora kinase A in early meiosis. By contrast, we observe an early, transient activation of MAPK, independent of Mos protein expression. MAPK directly phosphorylates CPEB on four residues (T22, T164, S184, S248), but not on S174, a key residue for activating CPEB function. Notably, XGef immunoprecipitates contain MAPK, and this complex can phosphorylate CPEB. MAPK may prime CPEB for phosphorylation on S174 by an as-yet-unidentified kinase or may activate this kinase.
Collapse
Affiliation(s)
- Brian T Keady
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA
| | | | | | | | | |
Collapse
|
23
|
Horn V, Thélu J, Garcia A, Albigès-Rizo C, Block MR, Viallet J. Functional interaction of Aurora-A and PP2A during mitosis. Mol Biol Cell 2007; 18:1233-41. [PMID: 17229885 PMCID: PMC1839003 DOI: 10.1091/mbc.e06-12-1152] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Entry into mitosis is a highly regulated process, promoted by the activated Cyclin B1/Cdk1 complex. Activation of this complex is controlled, in part, by the protein kinase Aurora-A, which is a member of a multigenic serine/threonine kinase family. In normal cells, Aurora-A activity is regulated, at least in part, by degradation through the APC-ubiquitin-proteasome pathway. It has recently been proposed that, in Xenopus, Aurora-A degradation can be inhibited by phosphorylation. It would thus be expected that a phosphatase activity would release this blockade at the end of mitosis. Here, we have shown that the protein phosphatase PP2A and Aurora-A are colocalized at the cell poles during mitosis in human cells and interact within the same complex. Using the PP2A inhibitor okadaic acid and an RNAi approach, we have shown that this interaction is functional within the cell. PP2A/Aurora-A interaction is promoted by an S51D mutation in Aurora-A and inhibited by a phosphomimetic peptide centered around Aurora-A S51, thereby strongly suggesting that PP2A controls Aurora-A degradation by dephosphorylating serine 51 in the A box of the human enzyme.
Collapse
Affiliation(s)
- Virginie Horn
- *Institut Albert Bonniot, Centre de Recherche Institut National de la Santé et de la Recherche Médicale, Université Joseph Fourier U 823, Equipe DySAD, Université Joseph Fourier Site Santé, BP 170, F38042, Grenoble Cedex 09, France; and
| | - Jacques Thélu
- *Institut Albert Bonniot, Centre de Recherche Institut National de la Santé et de la Recherche Médicale, Université Joseph Fourier U 823, Equipe DySAD, Université Joseph Fourier Site Santé, BP 170, F38042, Grenoble Cedex 09, France; and
| | - Alphonse Garcia
- Equipe Phosphatase, Unité de Chimie Organique, Institut Pasteur, 75724 Paris Cedex, France
| | - Corinne Albigès-Rizo
- *Institut Albert Bonniot, Centre de Recherche Institut National de la Santé et de la Recherche Médicale, Université Joseph Fourier U 823, Equipe DySAD, Université Joseph Fourier Site Santé, BP 170, F38042, Grenoble Cedex 09, France; and
| | - Marc R. Block
- *Institut Albert Bonniot, Centre de Recherche Institut National de la Santé et de la Recherche Médicale, Université Joseph Fourier U 823, Equipe DySAD, Université Joseph Fourier Site Santé, BP 170, F38042, Grenoble Cedex 09, France; and
| | - Jean Viallet
- *Institut Albert Bonniot, Centre de Recherche Institut National de la Santé et de la Recherche Médicale, Université Joseph Fourier U 823, Equipe DySAD, Université Joseph Fourier Site Santé, BP 170, F38042, Grenoble Cedex 09, France; and
| |
Collapse
|
24
|
Gotoh E, Durante M. Chromosome condensation outside of mitosis: mechanisms and new tools. J Cell Physiol 2006; 209:297-304. [PMID: 16810672 DOI: 10.1002/jcp.20720] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A basic principle of cell physiology is that chromosomes condense during mitosis. However, condensation can be uncoupled from mitotic events under certain circumstances. This phenomenon is known as "premature chromosome condensation (PCC)." PCC provides insights in the mechanisms of chromosome condensation, thus helping clarifying the key molecular events leading to the mitosis. Besides, PCC has proved to be an useful tool for analyzing chromosomes in interphase. For example, using PCC we can visualize genetic damage shortly after the exposure to clastogenic agents. More than 30 years ago, the first report of PCC in interphase cells fused to mitotic cells using Sendai virus was described (virus-mediated PCC). The method paved the way to a great number of fundamental discoveries in cytogenetics, radiation biology, and related fields, but it has been hampered by technical difficulties. The novel drug-induced PCC method was introduced about 10 years ago. While fusion-induced PCC exploits the action of external maturation/mitosis promoting factor (MPF), migrating from the inducer mitotic cell to the interphase recipient, drug-induced PCC exploits protein phosphatase inhibitors, which can activate endogenous intracellular MPF. This method is much simpler than fusion-induced PCC, and has already proven useful in different fields.
Collapse
Affiliation(s)
- Eisuke Gotoh
- Division of Genetic Resources, National Institute of Infectious Diseases, Tokyo, Japan
| | | |
Collapse
|
25
|
Hutterer A, Berdnik D, Wirtz-Peitz F, Zigman M, Schleiffer A, Knoblich JA. Mitotic activation of the kinase Aurora-A requires its binding partner Bora. Dev Cell 2006; 11:147-57. [PMID: 16890155 DOI: 10.1016/j.devcel.2006.06.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 05/18/2006] [Accepted: 06/08/2006] [Indexed: 12/31/2022]
Abstract
The protein kinase Aurora-A is required for centrosome maturation, spindle assembly, and asymmetric protein localization during mitosis. Here, we describe the identification of Bora, a conserved protein that is required for the activation of Aurora-A at the onset of mitosis. In the Drosophila peripheral nervous system, bora mutants have defects during asymmetric cell division identical to those observed in aurora-A. Furthermore, overexpression of bora can rescue defects caused by mutations in aurora-A. Bora is conserved in vertebrates, and both Drosophila and human Bora can bind to Aurora-A and activate the kinase in vitro. In interphase cells, Bora is a nuclear protein, but upon entry into mitosis, Bora is excluded from the nucleus and translocates into the cytoplasm in a Cdc2-dependent manner. We propose a model in which activation of Cdc2 initiates the release of Bora into the cytoplasm where it can bind and activate Aurora-A.
Collapse
Affiliation(s)
- Andrea Hutterer
- Institute of Molecular Biotechnology (IMBA), Dr Bohr Gasse 3-5, 1030 Vienna, Austria
| | | | | | | | | | | |
Collapse
|
26
|
Li Z, Tu X, Wang CC. Okadaic acid overcomes the blocked cell cycle caused by depleting Cdc2-related kinases in Trypanosoma brucei. Exp Cell Res 2006; 312:3504-16. [PMID: 16949574 DOI: 10.1016/j.yexcr.2006.07.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 07/19/2006] [Accepted: 07/21/2006] [Indexed: 10/24/2022]
Abstract
Mitosis and cytokinesis are highly coordinated in eukaryotic cells. But procyclic-form Trypanosoma brucei under G1 or mitotic arrest is still capable of dividing, resulting in anucleate daughter cells (zoids). Okadaic acid (OKA), an inhibitor of protein phosphatases PP1 and PP2A, is known to inhibit kinetoplast replication and cell division yielding multinucleate cells with single kinetoplasts. However, when OKA was applied to cells arrested in G1 or G2/M phase via RNAi knockdown of specific cdc2-related kinases (CRKs), DNA synthesis and nuclear division were resumed without kinetoplast replication or cell division, resulting in multinucleate cells as in the wild type. Cells arrested in G2/M via depleting the mitotic cyclin CycB2 or an aurora B kinase homologue TbAUK1 were, however, not released by OKA treatment. The phenomenon is thus similar to the OKA activation of Cdc2 in Xenopus oocyte by inhibiting PP2A [Maton, et al., Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A. J. Cell Sci. 118 (2005) 2485-2494]. A simultaneous knockdown of the seven PP1s or the PP2A catalytic subunit in T. brucei by RNA interference did not, however, result in multinucleate cells. This could be explained by assuming a negative regulation, either directly or indirectly, of CRK by an OKA-sensitive phosphatase, which could be a PP2A as in the Xenopus oocyte and a positive regulation of kinetoplast replication by an OKA-susceptible protein(s). Test of a PP2A-specific inhibitor, fostriecin, on cells arrested in G2/M via CRK depletion or a knockdown of the PP2A catalytic subunit from the CRK-depleted cells both showed a partial lift of the G2/M block without forming multinucleate cells. These observations support the abovementioned assumption and suggest the presence of a novel OKA-sensitive protein(s) regulating kinetoplast replication that still remains to be identified.
Collapse
Affiliation(s)
- Ziyin Li
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143-2280, USA
| | | | | |
Collapse
|
27
|
Zhao ZS, Lim JP, Ng YW, Lim L, Manser E. The GIT-associated kinase PAK targets to the centrosome and regulates Aurora-A. Mol Cell 2006; 20:237-49. [PMID: 16246726 DOI: 10.1016/j.molcel.2005.08.035] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Revised: 07/13/2005] [Accepted: 08/31/2005] [Indexed: 11/16/2022]
Abstract
Previously, we showed PAK-PIX-GIT targets and regulates focal adhesions; here, we uncover a different function for the complex at the centrosome. Active PAK1 is particularly evident in mitosis and phosphorylates the centrosomal adaptor GIT1 on serine 517. Interestingly, direct centrosome targeting activates the kinase via a process not requiring Rho GTPases; excision of the centrosome prevents this activation. Once activated, PAK1 dissociates from PIX/GIT but can bind to and phosphorylate the important centrosomal kinase Aurora-A. PAK1 promotes phosphorylation of Aurora-A on Thr288 and Ser342, which are key sites for kinase activation in mitosis. In vivo PAK activation causes an accumulation of activated Aurora-A; conversely, when betaPIX is depleted or PAK is inhibited, there is a delay in centrosome maturation. These observations may underlie reported effects of active PAK on cells, including histone H3 phosphorylation, alterations in centrosome number, and progression through mitosis.
Collapse
Affiliation(s)
- Zhuo-Shen Zhao
- GSK-IMCB Group, Institute of Molecular and Cell Biology, Proteos Building, 61 Biopolis Drive, Singapore 138673
| | | | | | | | | |
Collapse
|