scholarly journals AKT regulates mitotic progression of mammalian cells by phosphorylating MASTL

2018 ◽  
Author(s):  
Irfana Reshi ◽  
Misbah Un Nisa ◽  
Umer Farooq ◽  
Syed Qaaifah Gillani ◽  
Sameer Ahmad Bhat ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Critical Role ◽  
Mitotic Progression ◽  
Oncogenic Potential ◽  
Mitotic Kinases ◽  
Colorectal Cell ◽  
Phosphatase 2A ◽  
Important Regulator ◽  
Regulatory Loop

AbstractMicrotubule associated serine threonine like kinase (MASTL) has been recently identified as an important regulator of mitosis. By inhibiting protein phosphatase 2A, it plays a crucial role in activating one of the most important mitotic kinases known as cyclin dependent kinase1 (CDK1). MASTL has been seen to be up regulated in various types of cancers and is involved in tumor recurrence. It is activated by CDK1 through its auto regulatory loop but the complete mechanism of its activation is still unclear. In this study, we evaluated the regulation of MASTL via AKT during mitosis. Here we report that AKT phosphorylates MASTL at T299 which plays a critical role in its activation. Our results suggest that AKT increases CDK1 mediated phosphorylation and hence activity of MASTL which in turn promotes cell proliferation.. We also show that the oncogenic potential of AKT is augmented by MASTL activation as the AKT mediated oncogenesis in colorectal cell lines can be attenuated by inhibiting and/or silencing MASTL. In brief, we report that AKT has an important role in the progression of mitosis in mammalian cells and it does so through the phosphorylation and activation of MASTL.

scholarly journals AKT Regulates Mitotic Progression of Mammalian Cells by Phosphorylating MASTL, Leading to Protein Phosphatase 2A Inactivation

2020 ◽  
Vol 40 (10) ◽  
Author(s):  
Irfana Reshi ◽  
Misbah Un Nisa ◽  
Umer Farooq ◽  
Syed Qaaifah Gillani ◽  
Sameer Ahmed Bhat ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Protein Phosphatase 2A ◽  
Critical Role ◽  
Mitotic Progression ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Mitotic Kinases ◽  
Colorectal Cell ◽  
Phosphatase 2A

ABSTRACT Microtubule-associated serine/threonine kinase like (MASTL), also known as Greatwall (Gwl) kinase, has an important role in the regulation of mitosis. By inhibiting protein phosphatase 2A (PP2A), it plays a crucial role in activating one of the most important mitotic kinases, known as cyclin-dependent kinase 1 (CDK1). MASTL has been seen to be upregulated in various types of cancers and is also involved in tumor recurrence. It is activated by CDK1 through phosphorylations in the activation/T-loop, but the complete mechanism of its activation is still unclear. Here, we report that AKT phosphorylates MASTL at residue T299, which plays a critical role in its activation. Our results suggest that AKT increases CDK1-mediated phosphorylation and hence the activity of MASTL, which, in turn, promotes mitotic progression through PP2A inhibition. We also show that the oncogenic potential of AKT is augmented by MASTL activation, since AKT-mediated proliferation in colorectal cell lines can be attenuated by inhibiting and/or silencing MASTL. In brief, we report that AKT plays an important role in the progression of mitosis in mammalian cells and that it does so through the phosphorylation and activation of MASTL.

scholarly journals RanBP2 and SENP3 Function in a Mitotic SUMO2/3 Conjugation-Deconjugation Cycle on Borealin

2009 ◽  
Vol 20 (1) ◽  
pp. 410-418 ◽  
Author(s):  
Ulf R. Klein ◽  
Markus Haindl ◽  
Erich A. Nigg ◽  
Stefan Muller
Keyword(s):  
Mammalian Cells ◽  
Spindle Assembly Checkpoint ◽  
Critical Role ◽  
Specific Interaction ◽  
Regulatory Function ◽  
Mitotic Progression ◽  
Chromosome Congression ◽  
Chromosomal Passenger

The ubiquitin-like SUMO system controls cellular key functions, and several lines of evidence point to a critical role of SUMO for mitotic progression. However, in mammalian cells mitotic substrates of sumoylation and the regulatory components involved are not well defined. Here, we identify Borealin, a component of the chromosomal passenger complex (CPC), as a mitotic target of SUMO. The CPC, which additionally comprises INCENP, Survivin, and Aurora B, regulates key mitotic events, including chromosome congression, the spindle assembly checkpoint, and cytokinesis. We show that Borealin is preferentially modified by SUMO2/3 and demonstrate that the modification is dynamically regulated during mitotic progression, peaking in early mitosis. Intriguingly, the SUMO ligase RanBP2 interacts with the CPC, stimulates SUMO modification of Borealin in vitro, and is required for its modification in vivo. Moreover, the SUMO isopeptidase SENP3 is a specific interaction partner of Borealin and catalyzes the removal of SUMO2/3 from Borealin. These data thus delineate a mitotic SUMO2/3 conjugation–deconjugation cycle of Borealin and further assign a regulatory function of RanBP2 and SENP3 in the mitotic SUMO pathway.

scholarly journals PR48, a Novel Regulatory Subunit of Protein Phosphatase 2A, Interacts with Cdc6 and Modulates DNA Replication in Human Cells

2000 ◽  
Vol 20 (3) ◽  
pp. 1021-1029 ◽  
Author(s):  
Zhen Yan ◽  
Sergei A. Fedorov ◽  
Marc C. Mumby ◽  
R. Sanders Williams
Keyword(s):  
Dna Replication ◽  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Protein Phosphatase 2A ◽  
Specific Interaction ◽  
Regulatory Subunit ◽  
Amino Terminal ◽  
Phosphatase 2A ◽  
Initiation Of Dna Replication

ABSTRACT Initiation of DNA replication in eukaryotes is dependent on the activity of protein phosphatase 2A (PP2A), but specific phosphoprotein substrates pertinent to this requirement have not been identified. A novel regulatory subunit of PP2A, termed PR48, was identified by a yeast two-hybrid screen of a human placental cDNA library, using human Cdc6, an essential component of prereplicative complexes, as bait. PR48 binds specifically to an amino-terminal segment of Cdc6 and forms functional holoenzyme complexes with A and C subunits of PP2A. PR48 localizes to the nucleus of mammalian cells, and its forced overexpression perturbs cell cycle progression, causing a G1 arrest. These results suggest that dephosphorylation of Cdc6 by PP2A, mediated by a specific interaction with PR48, is a regulatory event controlling initiation of DNA replication in mammalian cells.

Antitumor antibiotic fostriecin covalently binds to cysteine-269 residue of protein phosphatase 2A catalytic subunit in mammalian cells

2009 ◽  
Vol 17 (23) ◽  
pp. 8113-8122 ◽  
Author(s):  
Toshifumi Takeuchi ◽  
Noriyuki Takahashi ◽  
Kazutomo Ishi ◽  
Tomoe Kusayanagi ◽  
Kouji Kuramochi ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Antitumor Antibiotic ◽  
Phosphatase 2A

scholarly journals Protein Phosphatase 2A (PP2A) Regulates EG5 to Control Mitotic Progression

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Yang Liu ◽  
Zhong Zhang ◽  
Hui Liang ◽  
Xuyang Zhao ◽  
Ling Liang ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Mitotic Progression ◽  
Phosphatase 2A

scholarly journals Phosphatase-Regulated Recruitment of the Spindle and Kinetochore Associated (SKA) Complex to Kinetochores

2017 ◽  
Author(s):  
Sushama Sivakumar ◽  
Gary J. Gorbsky
Keyword(s):  
Protein Phosphatase ◽  
Cell Cycle Progression ◽  
Spindle Checkpoint ◽  
Checkpoint Signaling ◽  
Mitotic Kinases ◽  
Feedback Cycle ◽  
Microtubule Attachment ◽  
Phosphatase 2A ◽  
Summary Statement ◽  
And Function

ABSTRACTKinetochores move chromosomes on dynamic spindle microtubules and regulate cell cycle progression by signaling the spindle checkpoint. The Spindle and Kinetochore-Associated (Ska) Complex, a hexamer composed of two copies of Ska1, Ska2 and Ska3, participates in both roles. The mitotic kinases, Cdk1, Aurora B, Plk1, Mps1 and Bub1 play key, overlapping tasks in regulating chromosome movement and checkpoint signaling. However, roles for the phosphatases that oppose these kinases are more poorly defined. Recently, we showed that Ska1 is important for recruiting protein phosphatase 1 (PP1) to kinetochores. Here we show that PP1 and protein phosphatase 2A (PP2A) both promote accumulation of Ska at kinetochores. Depletion of PP1 or PP2A by siRNA reduces Ska binding at kinetochores, impairs alignment of chromosomes to the spindle midplane, and causes metaphase delay or arrest, phenotypes also seen after depletion of Ska. Tethering of PP1 to the kinetochore protein Nuf2 promotes Ska recruitment to kinetochores, and reduces mitotic defects seen after Ska depletion. We propose that kinetochore-associated phosphatases generate a positive feedback cycle to reinforce Ska complex accumulation and function at kinetochores.SUMMARY STATEMENTPhosphatases reinforce recruitment of the Ska complex at kinetochores to stabilize microtubule attachment and oppose spindle checkpoint signaling.

Protein Phosphatase 2A (PP2A) Associates with Integrin αIIbβ3 and Regulates Adhesion to Fibrinogen.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1644-1644
Author(s):  
Kadekuzhi V. Vijayan ◽  
Yan Liu ◽  
Paul F. Bray
Keyword(s):  
Protein Phosphatase ◽  
Platelet Adhesion ◽  
Protein Phosphatase 2A ◽  
Critical Role ◽  
Specific Interaction ◽  
Cytoskeletal Proteins ◽  
Dependent Manner ◽  
Integrin Αiibβ3 ◽  
Knock Down ◽  
Phosphatase 2A

Abstract We have previously demonstrated that protein phosphatase 1 (PP1) associates constitutively with the integrin αIIb subunit and regulates myosin light chain phosphorylation. In this study, we considered whether other member of the serine/threonine (Ser/Thr) phosphatase family namely, protein phosphatase 2A (PP2A) associates with the integrin αIIbβ3. Co-immunoprecipitation assays using lysates from resting human platelets revealed the presence of a catalytic subunit of PP2A (PP2Ac) in the αIIb immunoprecipitates, and in a reciprocal experiment, αIIb was detected in the PP2Ac immunoprecipitates. In contrast, another platelet abundant Ser/Thr phosphatase, protein phosphatase 2C (PP2C) was not detected in the αIIb immunoprecipitates. Furthermore, the association of PP2Ac with integrin αIIbβ3 was also observed in 293 cells overexpressing αIIbβ3. These results indicate a constitutive and specific interaction of PP2Ac with the integrin αIIbβ3. Polystyrene beads coated with purified PP2Ac but not BSA supported the binding of purified integrin αIIbβ3 in a dose dependent manner, suggesting that the interaction of PP2Ac with αIIbβ3 was direct. Furthermore, purified PP2Ac as well as PP2Ac in lysates obtained from the resting platelets bound specifically to a biotinylated αIIb cytoplasmic peptide encompassing residues 985–995 but not to a scrambled peptide, suggesting that the integrin αIIb is sufficient to mediate the interaction of PP2Ac in vitro. The association of PP2Ac with the platelet integrin αIIbβ3 was not altered during platelet adhesion to fibrinogen (αIIbβ3 outside-in signaling) or during thrombin or ADP stimulation (inside-out signaling to αIIbβ3). In contrast, we have previously shown that integrin-bound PP1 dissociated from the αIIbβ3 complex upon platelet adhesion and thrombin-induced platelet activation. The association of PP2Ac with the integrin αIIbβ3 correlates well with the dephosphorylation of a PP2A substrate, extracellular-signal regulated kinase 2 (ERK2) during thrombin-induced platelet aggregation that we and others have previously demonstrated. More importantly, ERK2 dephosphorylation was not observed in platelets from Glanzmann thrombasthenic patients or in normal platelets pretreated with RGDS or integrilin, suggesting a critical role for integrin αIIbβ3 in the dephosphorylation of ERK2. To ascertain a physiological relevance for the PP2A-αIIbβ3 association, we used short interfering RNAs (siRNAs) to knock down the expression of PP2Ac in the 293/αIIbβ3 cells. Knock down was maximal (~55–70%) and specific to PP2Ac because PP1 and actin protein levels were not different between the control and PP2Ac siRNA treated cells. Consistent with the reduction in the PP2Ac protein level in the PP2Ac knock down cells there was ~70% reduction in the PP2Ac phosphatase activity, and a concomitant increased basal ERK2 phosphorylation. PP2Ac knock down significantly (P≤0.006) increased the adhesion of 293/αIIbβ3 cells to fibrinogen. The adhesion was αIIbβ3 specific because it could be abolished with an αIIbβ3 function blocking antibody (10E5). These findings supports a mechanism whereby the integrin associated Ser/Thr phosphatases might regulate αIIbβ3 adhesive functions via dephosphorylation of key cytoskeletal proteins.

scholarly journals Protein Phosphatase 2A Mediates Oxidative Stress Induced Apoptosis in Osteoblasts

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Chong-xin Huang ◽  
Bo Lv ◽  
Yue Wang
Keyword(s):  
Oxidative Stress ◽  
Lipid Peroxidation ◽  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Protein Phosphatase 2A ◽  
Bone Diseases ◽  
Dna Lesions ◽  
Major Protein ◽  
Phosphatase 2A ◽  
Induced Apoptosis

Osteoporosis is one of the most common bone diseases, which is characterized by a systemic impairment of bone mass and fragility fractures. Age-related oxidative stress is highly associated with impaired osteoblastic dysfunctions and subsequent osteoporosis. In osteoblasts (bone formation cells), reactive oxygen species (ROS) are continuously generated and further cause lipid peroxidation, protein damage, and DNA lesions, leading to osteoblastic dysfunctions, dysdifferentiations, and apoptosis. Although much progress has been made, the mechanism responsible for oxidative stress induced cellular alternations and osteoblastic toxicity is still not fully elucidated. Here, we demonstrate that protein phosphatase 2A (PP2A), a major protein phosphatase in mammalian cells, mediates oxidative stress induced apoptosis in osteoblasts. Our results showed that lipid peroxidation products (4-HNE) may induce dramatic oxidative stress, inflammatory reactions, and apoptosis in osteoblasts. These oxidative stress responses may ectopically activate PP2A phosphatase activity, which may be mediated by inactivation of AKT/mTOR pathway. Moreover, inhibition of PP2A activity by okadaic acid might partly prevent osteoblastic apoptosis under oxidative conditions. These findings may reveal a novel mechanism to clarify the role of oxidative stress for osteoblastic apoptosis and provide new possibilities for the treatment of related bone diseases, such as osteoporosis.

A critical role for the protein phosphatase 2A B′α regulatory subunit in dephosphorylation of sphingosine kinase 1

2011 ◽  
Vol 43 (3) ◽  
pp. 342-347 ◽  
Author(s):  
Melissa R. Pitman ◽  
Renae K. Barr ◽  
Briony L. Gliddon ◽  
Angus M. Magarey ◽  
Paul A.B. Moretti ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Critical Role ◽  
Sphingosine Kinase ◽  
Regulatory Subunit ◽  
Sphingosine Kinase 1 ◽  
Phosphatase 2A

scholarly journals Cyclin B–Cdk1 inhibits protein phosphatase PP2A-B55 via a Greatwall kinase–independent mechanism

2014 ◽  
Vol 204 (6) ◽  
pp. 881-889 ◽  
Author(s):  
Eiichi Okumura ◽  
Atsushi Morita ◽  
Mizuho Wakai ◽  
Satoru Mochida ◽  
Masatoshi Hara ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Cyclin B ◽  
Mitotic Progression ◽  
Independent Mechanism ◽  
M Phase ◽  
Dependent Inhibition ◽  
Phosphatase 2A ◽  
Initial Activation ◽  
Greatwall Kinase ◽  
Different Levels

Entry into M phase is governed by cyclin B–Cdk1, which undergoes both an initial activation and subsequent autoregulatory activation. A key part of the autoregulatory activation is the cyclin B–Cdk1–dependent inhibition of the protein phosphatase 2A (PP2A)–B55, which antagonizes cyclin B–Cdk1. Greatwall kinase (Gwl) is believed to be essential for the autoregulatory activation because Gwl is activated downstream of cyclin B–Cdk1 to phosphorylate and activate α-endosulfine (Ensa)/Arpp19, an inhibitor of PP2A-B55. However, cyclin B–Cdk1 becomes fully activated in some conditions lacking Gwl, yet how this is accomplished remains unclear. We show here that cyclin B–Cdk1 can directly phosphorylate Arpp19 on a different conserved site, resulting in inhibition of PP2A-B55. Importantly, this novel bypass is sufficient for cyclin B–Cdk1 autoregulatory activation. Gwl-dependent phosphorylation of Arpp19 is nonetheless necessary for downstream mitotic progression because chromosomes fail to segregate properly in the absence of Gwl. Such a biphasic regulation of Arpp19 results in different levels of PP2A-B55 inhibition and hence might govern its different cellular roles.

Sign in / Sign up

Export Citation Format

Share Document