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Ross AP, Zarbalis KS. The emerging roles of ribosome biogenesis in craniofacial development. Front Physiol 2014; 5:26. [PMID: 24550838 PMCID: PMC3912750 DOI: 10.3389/fphys.2014.00026] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 01/13/2014] [Indexed: 12/29/2022] Open
Abstract
Neural crest cells (NCCs) are a transient, migratory cell population, which originates during neurulation at the neural folds and contributes to the majority of tissues, including the mesenchymal structures of the craniofacial skeleton. The deregulation of the complex developmental processes that guide migration, proliferation, and differentiation of NCCs may result in a wide range of pathological conditions grouped together as neurocristopathies. Recently, due to their multipotent properties neural crest stem cells have received considerable attention as a possible source for stem cell based regenerative therapies. This exciting prospect underlines the need to further explore the developmental programs that guide NCC differentiation. This review explores the particular importance of ribosome biogenesis defects in this context since a specific interface between ribosomopathies and neurocristopathies exists as evidenced by disorders such as Treacher-Collins-Franceschetti syndrome (TCS) and Diamond-Blackfan anemia (DBA).
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Affiliation(s)
- Adam P Ross
- Department of Pathology and Laboratory Medicine, Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, University of California at Davis Sacramento, CA, USA
| | - Konstantinos S Zarbalis
- Department of Pathology and Laboratory Medicine, Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, University of California at Davis Sacramento, CA, USA
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2
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Ross AP, Mansilla MA, Choe Y, Helminski S, Sturm R, Maute RL, May SR, Hozyasz KK, Wójcicki P, Mostowska A, Davidson B, Adamopoulos IE, Pleasure SJ, Murray JC, Zarbalis KS. A mutation in mouse Pak1ip1 causes orofacial clefting while human PAK1IP1 maps to 6p24 translocation breaking points associated with orofacial clefting. PLoS One 2013; 8:e69333. [PMID: 23935987 PMCID: PMC3723895 DOI: 10.1371/journal.pone.0069333] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 06/08/2013] [Indexed: 01/05/2023] Open
Abstract
Orofacial clefts are among the most common birth defects and result in an improper formation of the mouth or the roof of the mouth. Monosomy of the distal aspect of human chromosome 6p has been recognized as causative in congenital malformations affecting the brain and cranial skeleton including orofacial clefts. Among the genes located in this region is PAK1IP1, which encodes a nucleolar factor involved in ribosomal stress response. Here, we report the identification of a novel mouse line that carries a point mutation in the Pak1ip1 gene. Homozygous mutants show severe developmental defects of the brain and craniofacial skeleton, including a median orofacial cleft. We recovered this line of mice in a forward genetic screen and named the allele manta-ray (mray). Our findings prompted us to examine human cases of orofacial clefting for mutations in the PAK1IP1 gene or association with the locus. No deleterious variants in the PAK1IP1 gene coding region were recognized, however, we identified a borderline association effect for SNP rs494723 suggesting a possible role for the PAK1IP1 gene in human orofacial clefting.
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Affiliation(s)
- Adam P. Ross
- Department of Pathology and Laboratory Medicine, University of California Davis, Sacramento, California, United States of America
| | - M. Adela Mansilla
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Youngshik Choe
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Simon Helminski
- Department of Pathology and Laboratory Medicine, University of California Davis, Sacramento, California, United States of America
| | - Richard Sturm
- Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany
| | - Roy L. Maute
- Institute for Cancer Genetics, Columbia University, New York City, New York, United States of America
| | - Scott R. May
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Kamil K. Hozyasz
- Department of Pediatrics, Institute of Mother and Child, Warsaw, Poland
| | - Piotr Wójcicki
- Department of Plastic Surgery, Wrocław Medical University, Polanica Zdroj, Poland
- Department of Plastic Surgery, Medical Centre, Polanica-Zdrój, Poland
| | - Adrianna Mostowska
- Department of Biochemistry and Molecular Biology, Poznan University of Medical Sciences, Poznan, Poland
| | - Beth Davidson
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Iannis E. Adamopoulos
- Department of Internal Medicine, University of California Davis, Sacramento, California, United States of America
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children Northern California, Sacramento, California, United States of America
| | - Samuel J. Pleasure
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Jeffrey C. Murray
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Konstantinos S. Zarbalis
- Department of Pathology and Laboratory Medicine, University of California Davis, Sacramento, California, United States of America
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children Northern California, Sacramento, California, United States of America
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3
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Yu W, Qiu Z, Gao N, Wang L, Cui H, Qian Y, Jiang L, Luo J, Yi Z, Lu H, Li D, Liu M. PAK1IP1, a ribosomal stress-induced nucleolar protein, regulates cell proliferation via the p53-MDM2 loop. Nucleic Acids Res 2010; 39:2234-48. [PMID: 21097889 PMCID: PMC3064775 DOI: 10.1093/nar/gkq1117] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Cell growth and proliferation are tightly controlled via the regulation of the p53–MDM2 feedback loop in response to various cellular stresses. In this study, we identified a nucleolar protein called PAK1IP1 as another regulator of this loop. PAK1IP1 was induced when cells were treated with chemicals that disturb ribosome biogenesis. Overexpression of PAK1IP1 inhibited cell proliferation by inducing p53-dependent G1 cell-cycle arrest. PAK1IP1 bound to MDM2 and inhibited its ability to ubiquitinate and to degrade p53, consequently leading to the accumulation of p53 levels. Interestingly, knockdown of PAK1IP1 in cells also inhibited cell proliferation and induced p53-dependent G1 arrest. Deficiency of PAK1IP1 increased free ribosomal protein L5 and L11 which were required for PAK1IP1 depletion-induced p53 activation. Taken together, our results reveal that PAK1IP1 is a new nucleolar protein that is crucial for rRNA processing and plays a regulatory role in cell proliferation via the p53–MDM2 loop.
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Affiliation(s)
- Weishi Yu
- The Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
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Ong YS, Tang BL, Loo LS, Hong W. p125A exists as part of the mammalian Sec13/Sec31 COPII subcomplex to facilitate ER-Golgi transport. ACTA ACUST UNITED AC 2010; 190:331-45. [PMID: 20679433 PMCID: PMC2922642 DOI: 10.1083/jcb.201003005] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
p125A is an accessory protein for COPII-mediated vesicle budding that links the Sec13/Sec31 and Sec23/24 subcomplexes. Coat protein II (COPII)–mediated export from the endoplasmic reticulum (ER) involves sequential recruitment of COPII complex components, including the Sar1 GTPase, the Sec23/Sec24 subcomplex, and the Sec13/Sec31 subcomplex. p125A was originally identified as a Sec23A-interacting protein. Here we demonstrate that p125A also interacts with the C-terminal region of Sec31A. The Sec31A-interacting domain of p125A is between residues 260–600, and is therefore a distinct domain from that required for interaction with Sec23A. Gel filtration and immunodepletion studies suggest that the majority of cytosolic p125A exists as a ternary complex with the Sec13/Sec31A subcomplex, suggesting that Sec 13, Sec31A, and p125A exist in the cytosol primarily as preassembled Sec13/Sec31A/p125A heterohexamers. Golgi morphology and protein export from the ER were affected in p125A-silenced cells. Our results suggest that p125A is part of the Sec13/Sec31A subcomplex and facilitates ER export in mammalian cells.
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Affiliation(s)
- Yan Shan Ong
- Cancer and Developmental Cell Biology Division, Institute of Molecular and Cell Biology, Singapore 138673, Singapore
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Kumar A, Molli PR, Pakala SB, Bui Nguyen TM, Rayala SK, Kumar R. PAK thread from amoeba to mammals. J Cell Biochem 2009; 107:579-85. [PMID: 19350548 DOI: 10.1002/jcb.22159] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The p21-activated kinases (PAKs) are signaling nodes that play a crucial role in cellular processes including cell motility, differentiation, survival, gene transcription, and hormone signaling. PAKs are highly conserved family of serine-threonine kinases that act as effector for small GTPases Rac and Cdc42. Most of our knowledge about PAK functions has been derived from genetic approaches in lower organisms and many of these functions are similar to that seen in mammalian cells. In this review, we have summarized the extensive information generated in lower eukaryotes and very briefly discussed the current status of PAKs in humans.
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Affiliation(s)
- Anupam Kumar
- Department of Biochemistry and Molecular Biology, George Washington University Medical Center, Washington, District of Columbia 20037, USA
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Wheatley E, Rittinger K. Interactions between Cdc42 and the scaffold protein Scd2: requirement of SH3 domains for GTPase binding. Biochem J 2009; 388:177-84. [PMID: 15631622 PMCID: PMC1186706 DOI: 10.1042/bj20041838] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The multi-domain protein Scd2 acts as a scaffold upon which the small GTPase Cdc42 (cell division cycle 42), its nucleotide-exchange factor Scd1 and the p21-activated kinase Shk1 assemble to regulate cell polarity and the mating response in fission yeast. In the present study, we show using isothermal titration calorimetry that Scd2 binds two molecules of active GTP-bound Cdc42 simultaneously, but independently of one another. The two binding sites have significantly different affinities, 21 nM and 3 microM, suggesting that they play distinct roles in the Shk1 signalling network. Each of the Cdc42-binding sites includes one of the SH3 (Src homology 3) domains of Scd2. Our data indicate that complex formation does not occur in a conventional manner via the conserved SH3 domain ligand-binding surface. Neither of the isolated SH3 domains is sufficient to interact with the GTPase, and they both require adjacent regions to either stabilize their conformations or contribute to the formation of the Cdc42-binding surface. Furthermore, we show that there is no evidence for an intramolecular PX-SH3 domain interaction, which could interfere with SH3 domain function. This work suggests that SH3 domains might contribute directly to signalling through small GTPases and thereby adds another aspect to the diverse nature of SH3 domains as protein-protein-interaction modules.
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Affiliation(s)
- Edward Wheatley
- Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
| | - Katrin Rittinger
- Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, U.K
- To whom correspondence should be addressed (email )
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7
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Schizosaccharomyces pombe Noc3 is essential for ribosome biogenesis and cell division but not DNA replication. EUKARYOTIC CELL 2008; 7:1433-40. [PMID: 18606828 DOI: 10.1128/ec.00119-08] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The initiation of eukaryotic DNA replication is preceded by the assembly of prereplication complexes (pre-RCs) at chromosomal origins of DNA replication. Pre-RC assembly requires the essential DNA replication proteins ORC, Cdc6, and Cdt1 to load the MCM DNA helicase onto chromatin. Saccharomyces cerevisiae Noc3 (ScNoc3), an evolutionarily conserved protein originally implicated in 60S ribosomal subunit trafficking, has been proposed to be an essential regulator of DNA replication that plays a direct role during pre-RC formation in budding yeast. We have cloned Schizosaccharomyces pombe noc3(+) (Spnoc3(+)), the S. pombe homolog of the budding yeast ScNOC3 gene, and functionally characterized the requirement for the SpNoc3 protein during ribosome biogenesis, cell cycle progression, and DNA replication in fission yeast. We showed that fission yeast SpNoc3 is a functional homolog of budding yeast ScNoc3 that is essential for cell viability and ribosome biogenesis. We also showed that SpNoc3 is required for the normal completion of cell division in fission yeast. However, in contrast to the proposal that ScNoc3 plays an essential role during DNA replication in budding yeast, we demonstrated that fission yeast cells do enter and complete S phase in the absence of SpNoc3, suggesting that SpNoc3 is not essential for DNA replication in fission yeast.
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García P, Tajadura V, García I, Sánchez Y. Role of Rho GTPases and Rho-GEFs in the regulation of cell shape and integrity in fission yeast. Yeast 2007; 23:1031-43. [PMID: 17072882 DOI: 10.1002/yea.1409] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Rho family of GTPases are highly conserved molecular switches that control some of the most fundamental processes of cell biology, including morphogenesis, vesicular transport, cell division and motility. Guanine nucleotide-exchange factors (GEFs) are directly responsible for the activation of Rho-family GTPases in response to extracellular stimuli. In fission yeast, there are seven Dbl-related GEFs and they activate six Rho-type GTPases within a particular spatio-temporal context. The failure to do so might have consequences reflected in aberrant phenotypes and in some cases lead to cell death. In this review, we briefly summarize the role of Rho GTPases and Rho-GEFs in the establishment and maintenance of cell polarity and cell integrity in Schizosaccharomyces pombe.
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Affiliation(s)
- Patricia García
- Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca and Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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9
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Saveanu C, Rousselle JC, Lenormand P, Namane A, Jacquier A, Fromont-Racine M. The p21-activated protein kinase inhibitor Skb15 and its budding yeast homologue are 60S ribosome assembly factors. Mol Cell Biol 2007; 27:2897-909. [PMID: 17308036 PMCID: PMC1899936 DOI: 10.1128/mcb.00064-07] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ribosome biogenesis is driven by a large number of preribosomal factors that associate with and dissociate from the preribosomal particles along the maturation pathway. We have previously shown that budding yeast Mak11, whose homologues in other eukaryotes were described as modulating a p21-activated protein kinase function, accumulates in Rlp24-associated pre-60S complexes when their maturation is impeded in Saccharomyces cerevisiae. The functional inactivation of WD40 repeat protein Mak11 interfered with the 60S rRNA maturation, led to a cell cycle delay in G(1), and blocked green fluorescent protein-tagged Rpl25 in the nucleoli of yeast cells, indicating an early role of Mak11 in ribosome assembly. Surprisingly, Mak11 inactivation also led to a dramatic destabilization of Rlp24. The suppression of the thermosensitive phenotype of a mak11 mutant by RLP24 overexpression and a direct in vitro interaction between Rlp24 and Mak11 suggest that Mak11 acts as an Rlp24 cofactor during early steps of 60S ribosomal subunit assembly. Moreover, we found that Skb15, the Mak11 homologue in Schizosaccharomyces pombe, also associated with preribosomes and affected 60S biogenesis in fission yeast. It is thus likely that the previously observed phenotypes for MAK11 homologues in other eukaryotes are secondary to the main function of these proteins in ribosome formation.
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Affiliation(s)
- Cosmin Saveanu
- Génétique des Interactions Macromoléculaires, Institut Pasteur, 25 rue du docteur Roux, 75724 Paris Cedex 15, France
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10
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Abstract
p21-activated kinases (Paks) are a highly conserved family of enzymes that bind to and are activated by small GTPases of the Cdc42 and Rac families. With the notable exception of plants, nearly all eukaryotes encode one or more Pak genes, indicating an ancient origin and important function for this family of enzymes. Genetic approaches in many different experimental systems, ranging from yeast to mice, are beginning to decipher the different functions of Paks. Although some of these functions are unique to a given organism, certain common themes have emerged, such as the activation of mitogen-activated protein kinase (MAPK) cascades and the regulation of cytoskeletal structure through effects on the actin and tubulin cytoskeletons.
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Affiliation(s)
- Clemens Hofmann
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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11
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Zhu Y, Wang Y, Xia C, Li D, Li Y, Zeng W, Yuan W, Liu H, Zhu C, Wu X, Liu M. WDR26: a novel Gbeta-like protein, suppresses MAPK signaling pathway. J Cell Biochem 2005; 93:579-87. [PMID: 15378603 DOI: 10.1002/jcb.20175] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
WD40 repeat proteins play important roles in a variety of cellular functions, including cell growth, proliferation, apoptosis, and intracellular signal transduction. Mitogen-activated protein kinases (MAPKs) are evolutionary conserved enzymes in cell signal transduction connecting cell-surface receptors to critical regulatory targets within cells and control cell survival, adaptation, and proliferation. Previous studies revealed that G-protein coupled receptors (GPCRs) play important roles in the signal transduction from extracellular stimuli to MAPKs and the WD40-containing Gbeta proteins as well as Gbeta-like proteins are involved in the stimulation and regulation of the MAPK signaling pathways. Here we report the identification and characterization of a novel human WD40 repeat protein, WD40 repeat protein 26 (WDR26). The cDNA of WDR26 is 3,729 bp, encoding a Gbeta-like protein of 514 amino acids in the cytoplasm. The protein is highly conserved in evolution across different species from yeast, Drosophila, mouse, to human. Northern blot analysis indicates that WDR26 is expressed in most of the examined human tissues, especially at a high level in skeletal muscle. Overexpression of WDR26 in the cell inhibits the transcriptional activities of ETS proteins, ELK-1 and c-fos serum response element (SRE), mediated by MEKK1. These results suggest that WDR26 may act as a negative regulator in MAPK signaling pathway and play an important role in cell signal transduction.
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Affiliation(s)
- Ying Zhu
- College of Life Sciences, Hunan Normal University, Changsha, 410081 Hunan, China
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Wu CF, Yang P, Traverso EE, Etkin LD, Marcus S. The Xenopus laevis morphogenetic factor, tumorhead, causes defects in polarized growth and cytokinesis in the fission yeast, Schizosaccharomyces pombe. Biochem Biophys Res Commun 2004; 325:439-44. [PMID: 15530412 DOI: 10.1016/j.bbrc.2004.10.046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Indexed: 10/26/2022]
Abstract
Tumorhead (TH) is a maternally expressed gene product that regulates neural tube morphogenesis in the amphibian, Xenopus laevis. Here we describe the effects of TH expression in the rod-shaped fission yeast, Schizosaccharomyces pombe. Expression of TH in S. pombe resulted in severe morphological defects, including ovoid, bottle-shaped, and enlarged cells. Multi-septated cells were also observed in TH expressing cultures, indicating that TH is inhibitory to a process required for the completion of cytokinesis. TH expression caused significant actin and microtubule cytoskeletal defects, including depolarization of the cortical F-actin cytoskeleton and increased microtubule formation. Immunostaining experiments showed that TH is localized to the cell cortex, cell tips, and septum in S. pombe cells. Localization of TH to the cell cortex was dependent on the S. pombe PAK homolog, Shk1. Moreover, TH expression was inhibitory to the growth of a mutant defective in Shk1 function, suggesting that TH may interact with a component(s) of a PAK-mediated morphogenetic regulatory pathway in S. pombe. Taken together, our findings demonstrate that S. pombe may be a useful model organism for identifying potential TH interacting factors.
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Affiliation(s)
- Chuan Fen Wu
- Department of Molecular Genetics and Program in Genes and Development, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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13
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Li Y, Chang EC. Schizosaccharomyces pombe Ras1 effector, Scd1, interacts with Klp5 and Klp6 kinesins to mediate cytokinesis. Genetics 2004; 165:477-88. [PMID: 14573463 PMCID: PMC1462777 DOI: 10.1093/genetics/165.2.477] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Fission yeast Scd1 is an exchange factor for Cdc42 and an effector of Ras1. In a screen for scd1 interacting genes, we isolated klp5 and klp6, which encode presumptive kinesins. Klp5 and Klp6 form a complex to control the same processes, which so far include microtubule dynamics and chromosome segregation. We showed that klp5 or klp6 inactivation in combination with the scd1 deletion (scd1delta) created a synthetic temperature-dependent growth defect. Further genetic analysis demonstrated that Klp5 and Klp6 interacted specifically with the Ras1-Scd1 pathway, but not with the Ras1-Byr2 pathway. In addition, Klp5 and Klp6 can stably associate with Scd1 and Cdc42. A deletion in the Scd1 C terminus, which contains the PB1 domain, prevented Scd1 binding to Klp5/6 and caused a growth defect in Klp5/6 mutant cells that is indistinguishable from that induced by scd1delta. Analysis of the double-mutant phenotype indicated that at the nonpermissive temperature, cells failed to undergo cytokinesis efficiently. These cells contained abnormal contractile rings in which F-actin and Mid1, a key regulator of F-actin ring formation and positioning, are mispositioned and fragmented. These data suggest that Klp5/6 cooperate with the Ras1-Scd1 pathway to influence proper formation of the contractile ring for cytokinesis.
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Affiliation(s)
- Yingchun Li
- Baylor College of Medicine, Department of Molecular and Cellular Biology, The Breast Center, Methodist Hospital, Houston, Texas 77030, USA
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14
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Yang P, Qyang Y, Bartholomeusz G, Zhou X, Marcus S. The novel Rho GTPase-activating protein family protein, Rga8, provides a potential link between Cdc42/p21-activated kinase and Rho signaling pathways in the fission yeast, Schizosaccharomyces pombe. J Biol Chem 2003; 278:48821-30. [PMID: 14506270 DOI: 10.1074/jbc.m306819200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The PAK family kinase, Shk1, is an essential regulator of polarized growth in the fission yeast, Schizosaccharomyces pombe. Here we describe the characterization of a novel member of the RhoGAP family, Rga8, identified from a two-hybrid screen for proteins that interact with the Shk1 kinase domain. Although deletion of the rga8 gene in wild type S. pombe cells results in no obvious phenotypic defects under normal growth conditions, it partially suppresses the cold-sensitive growth and morphological defects of S. pombe cells carrying a hypomorphic allele of the shk1 gene. By contrast, overexpression of rga8 is lethal to shk1-defective cells and causes morphological and cytokinesis defects in wild type S. pombe cells. Consistent with a role for Rga8 as a downstream target of Shk1, we show that the Rga8 protein is directly phosphorylated by Shk1 in vitro and phosphorylated in a Shk1-dependent fashion in S. pombe cells. Fluorescence photomicroscopy of the GFP-Rga8 fusion protein indicates that Rga8 is localized to the cell ends during interphase and to the septum-forming region during cytokinesis. In S. pombe cells carrying the orb2-34 allele of shk1, Rga8 exhibits a monopolar pattern of localization, providing evidence that Shk1 contributes to the regulation of Rga8 localization. Although molecular analyses suggest that Rga8 functions as a GAP for the S. pombe Rho1 GTPase, genetic experiments suggest that Rga8 and Rho1 have a positive functional interaction and that gain of Rho1 function, like gain of Rga8 function, is lethal to Shk1-defective cells. Our results suggest that Rga8 is a Shk1 substrate that negatively regulates Shk1-dependent growth control pathway(s) in S. pombe, potentially through interaction with the Rho1 GTPase.
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Affiliation(s)
- Peirong Yang
- Department of Molecular Genetics and Program in Genes and Development, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA
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15
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Kim H, Yang P, Catanuto P, Verde F, Lai H, Du H, Chang F, Marcus S. The kelch repeat protein, Tea1, is a potential substrate target of the p21-activated kinase, Shk1, in the fission yeast, Schizosaccharomyces pombe. J Biol Chem 2003; 278:30074-82. [PMID: 12764130 DOI: 10.1074/jbc.m302609200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The p21-activated kinase (PAK) homolog, Shk1, is a critical component of a multifunctional Ras/Cdc42/PAK complex required for viability, polarized growth and cell shape, and sexual differentiation in the fission yeast, Schizosaccharomyces pombe. Substrate targets of the Shk1 kinase have not previously been described. Here we show that the S. pombe cell polarity factor, Tea1, is directly phosphorylated by Shk1 in vitro. We demonstrate further that Tea1 is phosphorylated in S. pombe cells and that its level of phosphorylation is significantly reduced in cells defective in Shk1 function. Consistent with a role for Tea1 as a potential downstream effector of Shk1, we show that a tea1 null mutation rescues the Shk1 hyperactivity-induced lethal phenotype caused by loss of function of the essential Shk1 inhibitor, Skb15. All phenotypes associated with Skb15 loss, including defects in actin cytoskeletal organization, chromosome segregation, and cytokinesis, are suppressed by tea1 Delta, suggesting that Tea1 is a potential mediator of multiple Shk1 functions. S. pombe cells carrying a weak hypomorphic allele of shk1 together with a tea1 Delta mutation exhibit a cytokinesis defective phenotype that is significantly more severe than that observed in the respective single mutants, providing evidence that Shk1 and Tea1 cooperate to regulate cytokinesis. In addition, we show that S. pombe cells carrying the orb2-34 allele of shk1 exhibit a pattern of monopolar growth similar to that observed in tea1 Delta cells, suggesting that Shk1 and Tea1 may regulate one or more common processes involved in the regulation of polarized cell growth. Taken together, our results strongly implicate Tea1 as a potential substrate-effector of the Shk1 kinase.
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Affiliation(s)
- HyeWon Kim
- Department of Molecular Genetics and Program in Genes and Development, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA
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16
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Luo ZG, Wang Q, Zhou JZ, Wang J, Luo Z, Liu M, He X, Wynshaw-Boris A, Xiong WC, Lu B, Mei L. Regulation of AChR clustering by Dishevelled interacting with MuSK and PAK1. Neuron 2002; 35:489-505. [PMID: 12165471 DOI: 10.1016/s0896-6273(02)00783-3] [Citation(s) in RCA: 197] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
An important aspect of synapse development is the clustering of neurotransmitter receptors in the postsynaptic membrane. Although MuSK is required for acetylcholine receptor (AChR) clustering at the neuromuscular junction (NMJ), the underlying molecular mechanisms remain unclear. We report here that in muscle cells, MuSK interacts with Dishevelled (Dvl), a signaling molecule important for planar cell polarity. Disruption of the MuSK-Dvl interaction inhibits Agrin- and neuron-induced AChR clustering. Expression of dominant-negative Dvl1 in postsynaptic muscle cells reduces the amplitude of spontaneous synaptic currents at the NMJ. Moreover, Dvl1 interacts with downstream kinase PAK1. Agrin activates PAK, and this activation requires Dvl. Inhibition of PAK1 activity attenuates AChR clustering. These results demonstrate important roles of Dvl and PAK in Agrin/MuSK-induced AChR clustering and reveal a novel function of Dvl in synapse development.
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Affiliation(s)
- Zhen G Luo
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, 1530 Third Avenue South, Birmingham, AL 35294, USA
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Qyang Y, Yang P, Du H, Lai H, Kim H, Marcus S. The p21-activated kinase, Shk1, is required for proper regulation of microtubule dynamics in the fission yeast, Schizosaccharomyces pombe. Mol Microbiol 2002; 44:325-34. [PMID: 11972773 DOI: 10.1046/j.1365-2958.2002.02882.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The p21-activated kinase, Shk1, is required for the proper establishment of cell polarity in the fission yeast, Schizosaccharomyces pombe. We showed recently that loss of the essential Shk1 inhibitor, Skb15, causes significant spindle defects in fission yeast, thus implicating Shk1 as a potential regulator of microtubule dynamics. Here, we show that cells deficient in Shk1 function have malformed interphase microtubules and mitotic microtubule spindles, are hypersensitive to the microtubule-destabilizing drug thiabendazole (TBZ) and cold sensitive for growth. TBZ treatment causes a downregulation of Shk1 kinase activity, which increases rapidly after release of cells from the drug, thus providing a correlation between Shk1 kinase function and active microtubule polymerization. Consistent with a role for Shk1 as a regulator of microtubule dynamics, green fluorescent protein (GFP)-Shk1 fusion proteins localize to interphase microtubules and mitotic microtubule spindles, as well as to cell ends and septum-forming regions of fission yeast cells. We show that loss of Tea1, a cell end- and microtubule-localized protein previously implicated as a regulator of microtubule dynamics in fission yeast, exacerbates the growth and microtubule defects resulting from partial loss of Shk1 and that Shk1 localizes to illicit growth tips produced by tea1 mutant cells. Our results demonstrate that Shk1 is required for the proper regulation of microtubule dynamics in fission yeast and implicate Tea1 as a potential Shk1 regulator.
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Affiliation(s)
- Yibing Qyang
- Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston 77030, USA
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Current awareness on yeast. Yeast 2001; 18:1269-76. [PMID: 11561294 DOI: 10.1002/yea.689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Xia C, Ma W, Stafford LJ, Marcus S, Xiong WC, Liu M. Regulation of the p21-activated kinase (PAK) by a human Gbeta -like WD-repeat protein, hPIP1. Proc Natl Acad Sci U S A 2001; 98:6174-9. [PMID: 11371639 PMCID: PMC33441 DOI: 10.1073/pnas.101137298] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The family of p21-activated protein kinases (PAKs) is composed of serine-threonine kinases whose activity is regulated by the small guanosine triphosphatases (GTPases) Rac and Cdc42. In mammalian cells, PAKs have been implicated in the regulation of mitogen-activated protein cascades, cellular morphological and cytoskeletal changes, neurite outgrowth, and cell apoptosis. Although the ability of Cdc42 and Rac GTPases to activate PAK is well established, relatively little is known about the negative regulation of PAK or the identity of PAK cellular targets. Here, we describe the identification and characterization of a human PAK-interacting protein, hPIP1. hPIP1 contains G protein beta-like WD repeats and shares sequence homology with the essential fission yeast PAK regulator, Skb15, as well as the essential budding yeast protein, MAK11. Interaction of hPIP1 with PAK1 inhibits the Cdc42/Rac-stimulated kinase activity through the N-terminal regulatory domains of PAK1. Cotransfection of hPIP1 in mammalian cells inhibits PAK-mediated c-Jun N-terminal kinase and nuclear factor kappa B signaling pathways. Our results demonstrate that hPIP1 is a negative regulator of PAK and PAK signaling pathways.
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Affiliation(s)
- C Xia
- Center for Cancer Biology and Nutrition, Institute of Biosciences and Technology, and Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, Houston, TX 77030, USA
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