scholarly journals The study of the determinants controlling Arpp19 phosphatase-inhibitory activity reveals an Arpp19/PP2A-B55 feedback loop

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jean Claude Labbé ◽  
Suzanne Vigneron ◽  
Francisca Méchali ◽  
Perle Robert ◽  
Sylvain Roque ◽  
...  
Keyword(s):  
Cell Division ◽  
Inhibitory Activity ◽  
Temporal Pattern ◽  
Feedback Loop ◽  
Xenopus Oocytes ◽  
Cyclin B ◽  
High Affinity ◽  
Prophase I ◽  
Molecular Determinants ◽  
Greatwall Kinase

AbstractArpp19 is a potent PP2A-B55 inhibitor that regulates this phosphatase to ensure the stable phosphorylation of mitotic/meiotic substrates. At G2-M, Arpp19 is phosphorylated by the Greatwall kinase on S67. This phosphorylated Arpp19 form displays a high affinity to PP2A-B55 and a slow dephosphorylation rate, acting as a competitor of PP2A-B55 substrates. The molecular determinants conferring slow dephosphorylation kinetics to S67 are unknown. PKA also phosphorylates Arpp19. This phosphorylation performed on S109 is essential to maintain prophase I-arrest in Xenopus oocytes although the underlying signalling mechanism is elusive. Here, we characterize the molecular determinants conferring high affinity and slow dephosphorylation to S67 and controlling PP2A-B55 inhibitory activity of Arpp19. Moreover, we show that phospho-S109 restricts S67 phosphorylation by increasing its catalysis by PP2A-B55. Finally, we discover a double feed-back loop between these two phospho-sites essential to coordinate the temporal pattern of Arpp19-dependent PP2A-B55 inhibition and Cyclin B/Cdk1 activation during cell division.

scholarly journals The study of the determinants controlling Arpp19 phosphatase-inhibitory activity reveals a new Arpp19/PP2A-B55 feedback loop

2020 ◽  
Author(s):  
Jean Claude Labbé ◽  
Suzanne Vigneron ◽  
Francisca Méchali ◽  
Perle Robert ◽  
Cindy Genoud ◽  
...  
Keyword(s):  
Cell Division ◽  
Inhibitory Activity ◽  
Temporal Pattern ◽  
Feedback Loop ◽  
Xenopus Oocytes ◽  
Potent Inhibitor ◽  
Cyclin B ◽  
Signaling Mechanism ◽  
High Affinity ◽  
Molecular Determinants

ABSTRACTArpp19 is a potent inhibitor of PP2A-B55 that regulates this phosphatase to ensure the stable phosphorylation of mitotic/meiotic substrates. At G2-M, Arpp19 is phosphorylated by Greatwall on S67. This phosphorylated Arpp19 form displays a high affinity to PP2A-B55 and a slow dephosphorylation rate, acting as an “unfair” competitor of PP2A-B55 substrates. The molecular determinants conferring slow dephosphorylation kinetics to S67 are unknown. PKA also phosphorylates Arpp19. This phosphorylation performed on S109 is essential to maintain prophase I-arrest in Xenopus oocytes although the underlying signaling mechanism is elusive. Here, we characterized the molecular determinants conferring slow dephosphorylation to S67 and controlling PP2A-B55 inhibitory activity of Arpp19. Moreover, we showed that phospho-S109 restricts S67 phosphorylation by increasing its catalysis by PP2A-B55. Finally, we discovered a double feed-back loop between these two phospho-sites which is essential to coordinate the temporal pattern of Arpp19-dependent PP2A-B55 inhibition and Cyclin B/Cdk1 activation during cell division.

scholarly journals Fcp1 phosphatase controls Greatwall kinase to promote PP2A-B55 activation and mitotic progression

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Rosa Della Monica ◽  
Roberta Visconti ◽  
Nando Cervone ◽  
Angela Flavia Serpico ◽  
Domenico Grieco
Keyword(s):  
Cell Division ◽  
Protein Phosphorylation ◽  
Kinase Activity ◽  
Protein Phosphatases ◽  
Human Cells ◽  
Cyclin B ◽  
Major Protein ◽  
Phosphorylation Sites ◽  
Mitotic Progression ◽  
Greatwall Kinase

During cell division, progression through mitosis is driven by a protein phosphorylation wave. This wave namely depends on an activation-inactivation cycle of cyclin B-dependent kinase (Cdk) 1 while activities of major protein phosphatases, like PP1 and PP2A, appear directly or indirectly repressed by Cdk1. However, how Cdk1 inactivation is coordinated with reactivation of major phosphatases at mitosis exit still lacks substantial knowledge. We show here that activation of PP2A-B55, a major mitosis exit phosphatase, required the phosphatase Fcp1 downstream Cdk1 inactivation in human cells. During mitosis exit, Fcp1 bound Greatwall (Gwl), a Cdk1-stimulated kinase that phosphorylates Ensa/ARPP19 and converts these proteins into potent PP2A-B55 inhibitors during mitosis onset, and dephosphorylated it at Cdk1 phosphorylation sites. Fcp1-catalyzed dephosphorylation drastically reduced Gwl kinase activity towards Ensa/ARPP19 promoting PP2A-B55 activation. Thus, Fcp1 coordinates Cdk1 and Gwl inactivation to derepress PP2A-B55, generating a dephosphorylation switch that drives mitosis progression.

scholarly journals Characterization of DicB by partially masking its potent inhibitory activity of cell division

Open Biology ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 160082 ◽  
Author(s):  
Shaoyuan Yang ◽  
Hairun Pei ◽  
Xiaoying Zhang ◽  
Qiang Wei ◽  
Jia Zhu ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Growth ◽  
Inhibitory Activity ◽  
Terminal Segment ◽  
Molecular Determinants ◽  
N Terminus ◽  
First Time ◽  
Potent Inhibitory Activity

DicB, a protein encoded by the Kim (Qin) prophage in Escherichia coli , inhibits cell division through interaction with MinC. Thus far, characterization of DicB has been severely hampered owing to its potent activity which ceases cell division and leads to cell death. In this work, through fusing maltose-binding protein to the N-terminus of DicB (MBP–DicB), we successfully expressed and purified recombinant DicB that enabled in vitro analysis for the first time. More importantly, taking advantage of the reduced inhibitory activity of MBP–DicB, we were able to study its effects on cell growth and morphology. Inhibition of cell growth by MBP–DicB was systematically evaluated using various DicB constructs, and their corresponding effects on cell morphology were also investigated. Our results revealed that the N-terminal segment of DicB plays an essential functional role, in contrast to its C-terminal tail. The N-terminus of DicB is of critical importance as even the first amino acid (following the initial Met) could not be removed, although it could be mutated. This study provides the first glimpse of the molecular determinants underlying DicB's function.

NaCl-dependent expression of amiloride-blockable Na+ channel in Xenopus oocytes

1992 ◽  
Vol 262 (2) ◽  
pp. G244-G248 ◽  
Author(s):  
C. Asher ◽  
D. Singer ◽  
R. Eren ◽  
O. Yeger ◽  
N. Dascal ◽  
...  
Keyword(s):  
Xenopus Oocytes ◽  
The Other ◽  
Na Channel ◽  
Channel Activity ◽  
High Affinity ◽  
Other Hand ◽  
Exogenous Rna ◽  
Lower Intestine ◽  
Regulation Of Transport

RNA was isolated from chicken lower intestine (both colon and coprodeum) and injected into Xenopus oocytes. 22Na+ fluxes measured after 1-4 days demonstrated the induction of an amiloride-blockable pathway. The Na+ transporter expressed by the exogenous RNA had a high affinity to amiloride (inhibitory constant less than 0.1 microM), but was insensitive to ethylisopropyl amiloride, i.e., it is likely to be the apical Na+ channel. Functional channels were readily expressed in oocytes injected with RNA derived from chickens fed a low-NaCl diet. On the other hand, no channel activity was detected in oocytes injected with RNA isolated from chickens fed a high-NaCl diet. Thus the previously reported regulation of transport by the dietary NaCl intake involves modulations in the level of mRNA that codes either for the Na+ channel or a posttranscriptional regulator of the channel.

scholarly journals Expression cloning of a human renal cDNA that induces high affinity transport of L-cystine shared with dibasic amino acids in Xenopus oocytes

1993 ◽  
Vol 268 (20) ◽  
pp. 14842-14849
Author(s):  
J. Bertran ◽  
A. Werner ◽  
J. Chillarón ◽  
V. Nunes ◽  
J. Biber ◽  
...  
Keyword(s):  
Amino Acids ◽  
Xenopus Oocytes ◽  
Expression Cloning ◽  
High Affinity ◽  
Dibasic Amino Acids

scholarly journals Molecular mechanism of cytokinin-activated cell division in Arabidopsis

Science ◽  
2021 ◽  
Vol 371 (6536) ◽  
pp. 1350-1355
Author(s):  
Weibing Yang ◽  
Sandra Cortijo ◽  
Niklas Korsbo ◽  
Pawel Roszak ◽  
Katharina Schiessl ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Division ◽  
Histidine Kinase ◽  
Feedback Loop ◽  
Apical Meristem ◽  
Nuclear Accumulation ◽  
Cytokinin Signaling ◽  
Positive Feedback Loop ◽  
Nuclear Shuttling ◽  
Stimulate Cell Proliferation

Mitogens trigger cell division in animals. In plants, cytokinins, a group of phytohormones derived from adenine, stimulate cell proliferation. Cytokinin signaling is initiated by membrane-associated histidine kinase receptors and transduced through a phosphorelay system. We show that in the Arabidopsis shoot apical meristem (SAM), cytokinin regulates cell division by promoting nuclear shuttling of Myb-domain protein 3R4 (MYB3R4), a transcription factor that activates mitotic gene expression. Newly synthesized MYB3R4 protein resides predominantly in the cytoplasm. At the G2-to-M transition, rapid nuclear accumulation of MYB3R4—consistent with an associated transient peak in cytokinin concentration—feeds a positive feedback loop involving importins and initiates a transcriptional cascade that drives mitosis and cytokinesis. An engineered nuclear-restricted MYB3R4 mimics the cytokinin effects of enhanced cell proliferation and meristem growth.

scholarly journals Cells protect chromosome-microtubule attachments, independent of biorientation, using an Astrin-PP1 and CyclinB-CDK1 feedback loop

2020 ◽  
Author(s):  
Duccio Conti ◽  
Xinhong Song ◽  
Roshan L. Shrestha ◽  
Dominique Braun ◽  
Viji M Draviam
Keyword(s):  
Chromosomal Instability ◽  
Feedback Loop ◽  
Cyclin B ◽  
Macromolecular Structure ◽  
Aurora B ◽  
Unique Role ◽  
Spindle Poles ◽  
Microtubule Attachment ◽  
Segregation Of Chromosomes

Defects in chromosome-microtubule attachment can cause chromosomal instability, associated with infertility and aggressive cancers. Chromosome-microtubule attachment is mediated by a large macromolecular structure, the kinetochore. Kinetochore pairs are bioriented and pulled by microtubules from opposing spindle poles to ensure the equal segregation of chromosomes. Kinetochore-microtubule attachments lacking opposing-pull are detached by Aurora-B/Ipl1; yet, how mono-oriented attachments that are a prerequisite for biorientation, but lacking opposing-pull are spared is unclear. Using an RNAi-mediated screen, we uncover a unique role for the Astrin-SKAP complex in protecting mono-oriented attachments. We provide the first evidence for how a microtubule-end associated protein senses outer-kinetochore changes specific to end-on attachments and assembles into an outer kinetochore crescent to stabilise mature attachments. We find that Astrin-PP1 and Cyclin-B-CDK1 activities counteract each other to preserve mono-oriented attachments. Thus, cells are not only surveying chromosome-microtubule attachment errors, but they are also actively sensing and stabilising mature attachments independent of biorientation.

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