Protein phosphatase 1 down regulates ZYG-1 levels to limit centriole duplication

AbstractIn humans perturbations of centriole number are associated with tumorigenesis and microcephaly, therefore appropriate regulation of centriole duplication is critical. The C. elegans homolog of Plk4, ZYG-1, is required for centriole duplication, but our understanding of how ZYG-1 levels are regulated remains incomplete. We have identified the two PP1 orthologs, GSP-1 and GSP-2, and their regulators I-2szy-2 and SDS-22 as key regulators of ZYG-1 protein levels. We find that down-regulation of PP1 activity either directly, or by mutation of szy-2 or sds-22 can rescue the loss of centriole duplication associated with a zyg-1 hypomorphic allele. Suppression is achieved through an increase in ZYG-1 levels, and our data indicate that PP1 normally regulates ZYG-1 through a post-translational mechanism. While moderate inhibition of PP1 activity can restore centriole duplication to a zyg-1 mutant, strong inhibition of PP1 in a wild-type background leads to centriole amplification via the production of more than one daughter centriole. Our results thus define a new pathway that limits the number of daughter centrioles produced each cycle.Author SummaryThe centrosomes are responsible for organizing the mitotic spindle a microtubule-based structure that centers, then segregates, the chromosomes during cell division. When a cell divides it normally possesses two centrosomes, allowing it to build a bipolar spindle and accurately segregate the chromosomes to two daughter cells. Appropriate control of centrosome number is therefore crucial to maintaining genome stability. Centrosome number is largely controlled by their regulated duplication. In particular, the protein Plk4, which is essential for duplication, must be strictly limited as an overabundance leads to excess centrosome duplication. We have identified protein phosphatase 1 as a critical regulator of the C. elegans Plk4 homolog (known as ZYG-1). When protein phosphatase 1 is down-regulated, ZYG-1 levels increase leading to centrosome amplification. Thus our work identifies a novel mechanism that limits centrosome duplication.

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Establishment of gut fate in the E lineage of C. elegans: the roles of lineage-dependent mechanisms and cell interactions

Development ◽

10.1242/dev.118.4.1267 ◽

1993 ◽

Vol 118 (4) ◽

pp. 1267-1277 ◽

Cited By ~ 14

Author(s):

B. Goldstein

Keyword(s):

Cell Interactions ◽

The Other ◽

Cell Contact ◽

Cell Stage ◽

C Elegans ◽

Daughter Cells ◽

Intact Embryo ◽

A Cell ◽

Random Position ◽

Recombination Experiments

The gut of C. elegans derives from all the progeny of the E blastomere, a cell of the eight cell stage. Previous work has shown that gut specification requires an induction during the four cell stage (Goldstein, B. (1992) Nature 357, 255–257). Blastomere isolation and recombination experiments were done to determine which parts of the embryo can respond to gut induction. Normally only the posterior side of the EMS blastomere contacts the inducing cell, P2. When P2 was instead placed in a random position on an isolated EMS, gut consistently differentiated from the daughter of EMS contacting P2, indicating that any side of EMS can respond to gut induction. Additionally, moving P2 around to the opposite side of EMS in an otherwise intact embryo caused EMS's two daughter cells to switch lineage timings, and gut to differentiate from the descendents of what normally would be the MS blastomere. The other cells of the four cell stage, ABa, ABp, and P2, did not form gut when placed in contact with the inducer. To determine whether any other inductions are involved in gut specification, timed blastomere isolations were done at the two and eight cell stages. In the absence of cell contact at the two cell stage, segregation of gut fate proceeded normally at both the two and four cell stages. Gut fate also segregated properly in the absence of cell contact at the eight cell stage. A model is presented for the roles of lineage-dependent mechanisms and cell interactions in establishing gut fate in the E lineage.

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Wortmannin inhibits insulin-stimulated activation of protein phosphatase 1 in rat cardiomyocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.276.5.h1520 ◽

1999 ◽

Vol 276 (5) ◽

pp. H1520-H1526 ◽

Cited By ~ 4

Author(s):

Jane P. de Luca ◽

Alice K. Garnache ◽

Jill Rulfs ◽

Thomas B. Miller

Keyword(s):

Protein Phosphatase ◽

Glycogen Synthase ◽

Protein Phosphatase 1 ◽

Rat Cardiomyocytes ◽

Major Function ◽

Pi3k Inhibitors ◽

Protein Levels ◽

Pi3k Activity ◽

Insulin Dependent ◽

Phosphatase Activation

A major function of insulin in target tissues is the activation of glycogen synthase. Phosphatidylinositol 3-kinase (PI3K) has been implicated in the insulin-induced activation of glycogen synthase, although the true function of this enzyme remains unclear. Data presented here demonstrate that the PI3K inhibitors wortmannin and LY-294002 block the insulin-stimulated activation of protein phosphatase 1 (PP1) in rat ventricular cardiomyocytes. This loss of phosphatase activation mimics that seen in diabetic cardiomyocytes, in which insulin stimulation fails to activate both PP1 and glycogen synthase. Interestingly, in diabetic cells, insulin stimulated PI3K activity to 300% of that in untreated controls, whereas this activity was increased by only 77% in normal cells. PI3K protein levels, however, were similar in normal and diabetic cells. Our results indicate that PI3K is involved in the stimulation of glycogen synthase activity by insulin through the regulation of PP1. The inability of insulin to stimulate phosphatase activity in diabetic cells, despite a significant increase in PI3K activity, suggests a defect in the insulin signaling pathway that contributes to the pathology of insulin-dependent diabetes.

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NIMA-related kinase 2 (Nek2), a cell-cycle-regulated protein kinase localized to centrosomes, is complexed to protein phosphatase 1

Biochemical Journal ◽

10.1042/0264-6021:3490509 ◽

2000 ◽

Vol 349 (2) ◽

pp. 509 ◽

Cited By ~ 55

Author(s):

Nicholas R. HELPS ◽

Xinmei LUO ◽

Hazel M. BARKER ◽

Patricia T.W. COHEN

Keyword(s):

Cell Cycle ◽

Protein Kinase ◽

Protein Phosphatase ◽

Protein Phosphatase 1 ◽

A Cell

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Protein Phosphatase 1 Down Regulates ZYG-1 Levels to Limit Centriole Duplication

PLoS Genetics ◽

10.1371/journal.pgen.1006543 ◽

2017 ◽

Vol 13 (1) ◽

pp. e1006543 ◽

Cited By ~ 11

Author(s):

Nina Peel ◽

Jyoti Iyer ◽

Anar Naik ◽

Michael P. Dougherty ◽

Markus Decker ◽

...

Keyword(s):

Protein Phosphatase ◽

Protein Phosphatase 1 ◽

Centriole Duplication

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The Unresolved Problem of DNA Bridging

Genes ◽

10.3390/genes9120623 ◽

2018 ◽

Vol 9 (12) ◽

pp. 623 ◽

Cited By ~ 13

Author(s):

María Fernández-Casañas ◽

Kok-Lung Chan

Keyword(s):

Chromosome Segregation ◽

Genome Stability ◽

Genetic Material ◽

Genome Integrity ◽

Cellular Division ◽

Daughter Cells ◽

Dna Replication And Repair ◽

A Cell ◽

Chromosome Separation ◽

Last Stage

Accurate duplication and transmission of identical genetic information into offspring cells lies at the heart of a cell division cycle. During the last stage of cellular division, namely mitosis, the fully replicated DNA molecules are condensed into X-shaped chromosomes, followed by a chromosome separation process called sister chromatid disjunction. This process allows for the equal partition of genetic material into two newly born daughter cells. However, emerging evidence has shown that faithful chromosome segregation is challenged by the presence of persistent DNA intertwining structures generated during DNA replication and repair, which manifest as so-called ultra-fine DNA bridges (UFBs) during anaphase. Undoubtedly, failure to disentangle DNA linkages poses a severe threat to mitosis and genome integrity. This review will summarize the possible causes of DNA bridges, particularly sister DNA inter-linkage structures, in an attempt to explain how they may be processed and how they influence faithful chromosome segregation and the maintenance of genome stability.

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The PP1 regulator PPP1R2 coordinately regulates AURKA and PP1 to control centrosome phosphorylation and maintain central spindle architecture

BMC Molecular and Cell Biology ◽

10.1186/s12860-020-00327-5 ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Alan-Michael Bresch ◽

Nadiya Yerich ◽

Rong Wang ◽

Ann O. Sperry

Keyword(s):

Protein Phosphatase ◽

Cell Cycle Progression ◽

Protein Phosphatase 1 ◽

Regulatory Subunit ◽

Aurora A Kinase ◽

Central Spindle ◽

Phosphorylation State ◽

Daughter Cells ◽

Spindle Structure ◽

In Cells

Abstract Background Maintenance of centrosome number in cells is essential for accurate distribution of chromosomes at mitosis and is dependent on both proper centrosome duplication during interphase and their accurate distribution to daughter cells at cytokinesis. Two essential regulators of cell cycle progression are protein phosphatase 1 (PP1) and Aurora A kinase (AURKA), and their activities are each regulated by the PP1 regulatory subunit, protein phosphatase 1 regulatory subunit 2 (PPP1R2). We observed an increase in centrosome number after overexpression of these proteins in cells. Each of these proteins is found on the midbody in telophase and overexpression of PPP1R2 and its mutants increased cell ploidy and disrupted cytokinesis. This suggests that the increase in centrosome number we observed in PPP1R2 overexpressing cells was a consequence of errors in cell division. Furthermore, overexpression of PPP1R2 and its mutants increased midbody length and disrupted midbody architecture. Additionally, we show that overexpression of PPP1R2 alters activity of AURKA and PP1 and their phosphorylation state at the centrosome. Results Overexpression of PPP1R2 caused an increase in the frequency of supernumerary centrosomes in cells corresponding to aberrant cytokinesis reflected by increased nuclear content and cellular ploidy. Furthermore, AURKA, PP1, phospho PPP1R2, and PPP1R2 were all localized to the midbody at telophase, and PP1 localization there was dependent on binding of PPP1R2 with PP1 and AURKA as well as its phosphorylation state. Additionally, overexpression of both PPP1R2 and its C-terminal AURKA binding site altered enzymatic activity of AURKA and PP1 at the centrosome and disrupted central spindle structure. Conclusions Results from our study reveal the involvement of PPP1R2 in coordinating PP1 and AURKA activity during cytokinesis. Overexpression of PPP1R2 or its mutants disrupted the midbody at cytokinesis causing accumulation of centrosomes in cells. PPP1R2 recruited PP1 to the midbody and interference with its targeting resulted in elongated and severely disrupted central spindles supporting an important role for PPP1R2 in cytokinesis.

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Use of cell doublets for studying cytokinesis regulation reveals a new form of cytokinesis regression

10.21203/rs.3.rs-730080/v1 ◽

2021 ◽

Author(s):

◽

Einat Panet ◽

Shira Huri Ohev Shalom ◽

Ohad Kraus ◽

Irit Shoval ◽

...

Keyword(s):

Cell Division ◽

Mitotic Spindle ◽

Protein Phosphatase ◽

Protein Phosphatase 1 ◽

Intercellular Bridge ◽

Microtubule Network ◽

Aurora Kinases ◽

Daughter Cells ◽

Chemical Inhibition ◽

Chromatin Bridges

Abstract Cytokinesis mediates separation of daughter cells at the end of cell division. We have developed a high-throughput approach for monitoring cell-autonomous cytokinesis in non-adherent cells. Focusing on cytokinesis termination, we show that chemical inhibition of protein phosphatase 1 (PP1) and PP2A specifically in late cytokinesis activates cytokinesis regression, which is distinct from any known cytokinesis failure, and is not a by-product of abnormal furrow ingression or chromatin bridges. This process is characterized by the formation of cortical blebs primarily at the intercellular bridge, reopening of the cleavage furrow and reassembly of an interphase-like microtubule network, but not by chromatin recondensation and mitotic spindle formation. Finally, cytokinesis regression is suppressed by chemical inhibition of aurora kinases but not Cdk1 or PLK1. Altogether, our results highlight a hitherto uncharacterized facet of the counter-activity of PP1/PP2A and aurora kinases in the final step of cell division, which ultimately secure the conclusion of cytokinesis, thereby preventing polyploidy and genomic instability.

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