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Annual Review of Pharmacology and... 2014Precise control of the balance between protein phosphorylation, catalyzed by protein kinases, and protein dephosphorylation, catalyzed by protein phosphatases, is... (Review)
Review
Precise control of the balance between protein phosphorylation, catalyzed by protein kinases, and protein dephosphorylation, catalyzed by protein phosphatases, is essential for cellular homeostasis. Dysregulation of this balance leads to pathophysiological states, driving diseases such as cancer, heart disease, and diabetes. Aberrant phosphorylation of components of the pathways that control cell growth and cell survival are particularly prevalent in cancer. One of the most studied tumor suppressors in these pathways is the lipid phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome ten), which dephosphorylates the lipid second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3), thus preventing activation of the oncogenic kinase AKT (v-akt murine thymoma viral oncogene homolog). In 2005, the discovery of a family of protein phosphatases whose members directly dephosphorylate and inactivate AKT introduced a new negative regulator of the phosphoinositide 3-kinase (PI3K) oncogenic pathway. Pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP) isozymes comprise a novel tumor suppressor family whose two members, PHLPP1 and PHLPP2, are deleted as frequently as PTEN in cancers such as those of the prostate. PHLPP is thus a novel therapeutic target to suppress oncogenic pathways and is a potential candidate biomarker to stratify patients for the appropriate targeted therapeutics. This review discusses the role of PHLPP in terminating AKT signaling and how pharmacological intervention would impact this pathway.
Topics: DNA Primers; Gene Expression Regulation; Humans; Male; Molecular Targeted Therapy; Nuclear Proteins; Phosphoprotein Phosphatases; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-akt; Signal Transduction
PubMed: 24392697
DOI: 10.1146/annurev-pharmtox-011112-140338 -
Cell Apr 2020Protein phosphatase 2A (PP2A) enzymes can suppress tumors, but they are often inactivated in human cancers overexpressing inhibitory proteins. Here, we identify a class...
Protein phosphatase 2A (PP2A) enzymes can suppress tumors, but they are often inactivated in human cancers overexpressing inhibitory proteins. Here, we identify a class of small-molecule iHAPs (improved heterocyclic activators of PP2A) that kill leukemia cells by allosterically assembling a specific heterotrimeric PP2A holoenzyme consisting of PPP2R1A (scaffold), PPP2R5E (B56ε, regulatory), and PPP2CA (catalytic) subunits. One compound, iHAP1, activates this complex but does not inhibit dopamine receptor D2, a mediator of neurologic toxicity induced by perphenazine and related neuroleptics. The PP2A complex activated by iHAP1 dephosphorylates the MYBL2 transcription factor on Ser241, causing irreversible arrest of leukemia and other cancer cells in prometaphase. In contrast, SMAPs, a separate class of compounds, activate PP2A holoenzymes containing a different regulatory subunit, do not dephosphorylate MYBL2, and arrest tumor cells in G1 phase. Our findings demonstrate that small molecules can serve as allosteric switches to activate distinct PP2A complexes with unique substrates.
Topics: Apoptosis; Cell Cycle Proteins; Cell Line, Tumor; Enzyme Activators; G1 Phase; Humans; Multiprotein Complexes; Phenothiazines; Phosphorylation; Protein Phosphatase 2; Protein Subunits; Trans-Activators; Transcription Factors
PubMed: 32315619
DOI: 10.1016/j.cell.2020.03.051 -
Scientific Reports Feb 2018Dishevelled (Dvl) family proteins are key mediators of Wnt signalling and function in both canonical and noncanonical branches. Dvl2, the most studied Dvl protein, is...
Dishevelled (Dvl) family proteins are key mediators of Wnt signalling and function in both canonical and noncanonical branches. Dvl2, the most studied Dvl protein, is extensively regulated by phosphorylation. Several kinases were found to be critical for Dvl2 localisation, stability control and functional segregation. For example, S143-phosphorylated Dvl2 was detected, together with CK1δ/ε, at the centrosome and basal body of primary cilia and plays pivotal roles during ciliogenesis. However, relatively less is known about Dvl dephosphorylation and the phosphatases involved. Here, we identified PP5 (PPP5C) as a phosphatase of Dvl2. PP5 interacts with and can directly dephosphorylate Dvl2. Knockdown of PP5 caused elevated Dvl2 phosphorylation both at the basal level and upon Wnt stimulation. In the Dvl2 protein, S143, the 10B5 cluster and other sites were dephosphorylated by PP5. Interestingly, comparison of PP5 with PP2A, another known Dvl2 phosphatase, revealed that PP5 and PP2A are not fully redundant in the regulation of Dvl2 phosphorylation status. In hTERT-RPE1 cells, PP5 was found at the basal body of cilia, where S143-phosphorylated Dvl2 also resides. Functional assays revealed modest effects on ciliogenesis after PP5 depletion or over-expression. Taken together, our results provided evidence to suggest PP5 as a new phosphatase for Dvl2.
Topics: Cells, Cultured; Cilia; Dishevelled Proteins; HEK293 Cells; HeLa Cells; Humans; MCF-7 Cells; Nuclear Proteins; Phosphoprotein Phosphatases; Phosphorylation; Proteolysis; Retinal Pigment Epithelium; Signal Transduction; Wnt Proteins
PubMed: 29426949
DOI: 10.1038/s41598-018-21124-3 -
The EMBO Journal Oct 2022Dynamic regulation of phosphorylation and dephosphorylation of histones is essential for eukaryotic transcription, but the enzymes engaged in histone dephosphorylation...
Dynamic regulation of phosphorylation and dephosphorylation of histones is essential for eukaryotic transcription, but the enzymes engaged in histone dephosphorylation are not fully explored. Here, we show that the tyrosine phosphatase SHP-1 dephosphorylates histone H2B and plays a critical role during transition from the initiation to the elongation stage of transcription. Nuclear-localized SHP-1 is associated with the Paf1 complex at chromatin and dephosphorylates H2B at tyrosine 121. Moreover, knockout of SHP-1, or expression of a mutant mimicking constitutive phosphorylation of H2B Y121, leads to a reduction in genome-wide H2B ubiquitination, which subsequently causes defects in RNA polymerase II-dependent transcription. Mechanistically, we demonstrate that Y121 phosphorylation precludes H2B's interaction with the E2 enzyme, indicating that SHP-1-mediated dephosphorylation of this residue may be a prerequisite for efficient H2B ubiquitination. Functionally, we find that SHP-1-mediated H2B dephosphorylation contributes to maintaining basal autophagic flux in cells through the efficient transcription of autophagy and lysosomal genes. Collectively, our study reveals an important modification of histone H2B regulated by SHP-1 that has a role during eukaryotic transcription.
Topics: Chromatin; Histones; Phosphoric Monoester Hydrolases; Protein Tyrosine Phosphatase, Non-Receptor Type 6; RNA Polymerase II; Transcription, Genetic; Tyrosine; Ubiquitination
PubMed: 35938192
DOI: 10.15252/embj.2021109720 -
Frontiers in Cell and Developmental... 2019Cell-cell adhesion plays a key role in the maintenance of the epithelial barrier and apicobasal cell polarity, which is crucial for homeostasis. Disruption of cell-cell... (Review)
Review
Cell-cell adhesion plays a key role in the maintenance of the epithelial barrier and apicobasal cell polarity, which is crucial for homeostasis. Disruption of cell-cell adhesion is a hallmark of numerous pathological conditions, including invasive carcinomas. Adhesion between apposing cells is primarily regulated by three types of junctional structures: desmosomes, adherens junctions, and tight junctions. Cell junctional structures are highly regulated multiprotein complexes that also serve as signaling platforms to control epithelial cell function. The biogenesis, integrity, and stability of cell junctions is controlled by complex regulatory interactions with cytoskeletal and polarity proteins, as well as modulation of key component proteins by phosphorylation/dephosphorylation processes. Not surprisingly, many essential signaling molecules, including protein Ser/Thr phosphatase 2A (PP2A) are associated with intercellular junctions. Here, we examine how major PP2A enzymes regulate epithelial cell-cell junctions, either directly by associating with and dephosphorylating component proteins, or indirectly by affecting signaling pathways that control junctional integrity and cytoskeletal dynamics. PP2A deregulation has severe consequences on the stability and functionality of these structures, and disruption of cell-cell adhesion and cell polarity likely contribute to the link between PP2A dysfunction and human carcinomas.
PubMed: 30895176
DOI: 10.3389/fcell.2019.00030 -
Molecular & Cellular Proteomics : MCP Aug 2023Protein phosphorylation is an essential regulatory mechanism that controls most cellular processes, including cell cycle progression, cell division, and response to...
Protein phosphorylation is an essential regulatory mechanism that controls most cellular processes, including cell cycle progression, cell division, and response to extracellular stimuli, among many others, and is deregulated in many diseases. Protein phosphorylation is coordinated by the opposing activities of protein kinases and protein phosphatases. In eukaryotic cells, most serine/threonine phosphorylation sites are dephosphorylated by members of the Phosphoprotein Phosphatase (PPP) family. However, we only know for a few phosphorylation sites which specific PPP dephosphorylates them. Although natural compounds such as calyculin A and okadaic acid inhibit PPPs at low nanomolar concentrations, no selective chemical PPP inhibitors exist. Here, we demonstrate the utility of endogenous tagging of genomic loci with an auxin-inducible degron (AID) as a strategy to investigate specific PPP signaling. Using Protein Phosphatase 6 (PP6) as an example, we demonstrate how rapidly inducible protein degradation can be employed to identify dephosphorylation sites and elucidate PP6 biology. Using genome editing, we introduce AID-tags into each allele of the PP6 catalytic subunit (PP6c) in DLD-1 cells expressing the auxin receptor Tir1. Upon rapid auxin-induced degradation of PP6c, we perform quantitative mass spectrometry-based proteomics and phosphoproteomics to identify PP6 substrates in mitosis. PP6 is an essential enzyme with conserved roles in mitosis and growth signaling. Consistently, we identify candidate PP6c-dependent dephosphorylation sites on proteins implicated in coordinating the mitotic cell cycle, cytoskeleton, gene expression, and mitogen-activated protein kinase (MAPK) and Hippo signaling. Finally, we demonstrate that PP6c opposes the activation of large tumor suppressor 1 (LATS1) by dephosphorylating Threonine 35 (T35) on Mps One Binder (MOB1), thereby blocking the interaction of MOB1 and LATS1. Our analyses highlight the utility of combining genome engineering, inducible degradation, and multiplexed phosphoproteomics to investigate signaling by individual PPPs on a global level, which is currently limited by the lack of tools for specific interrogation.
Topics: Humans; Proteolysis; Protein Serine-Threonine Kinases; Phosphoprotein Phosphatases; Phosphorylation; Threonine; Colorectal Neoplasms; Protein Phosphatase 2
PubMed: 37392812
DOI: 10.1016/j.mcpro.2023.100614 -
Molecular Therapy. Nucleic Acids Sep 2023We have shown previously that polymorphism of activating transcription factor 6 (ATF6) is associated with susceptibility to hepatocellular carcinoma (HCC). Therefore,...
We have shown previously that polymorphism of activating transcription factor 6 (ATF6) is associated with susceptibility to hepatocellular carcinoma (HCC). Therefore, genes down-regulated by ATF6 might play a tumor-suppressing role. In the present study, we identified that expression of protein phosphatase magnesium- or manganous-dependent 1H (PPM1H) mRNA and protein can be inhibited by ATF6 in hepatoma cells and mice with liver knockdown. Tumor tissues from 134 HCC patients were analyzed by immunohistochemistry, and PPM1H exhibited higher expression levels in adjacent para-cancer tissues than in HCC tissues. Therefore, patients with higher expression of PPM1H had a better prognosis. PPM1H inhibited proliferation, migration, and invasion of hepatoma cells. In addition, PPM1H inhibited induced HCC nodule formation as well as tumor xenograft growth in diethylnitrosamine/CCl-induced HCC mouse model and nude mouse tumorigenicity assay, respectively. A 3D model of PPM1H was obtained by homology multi-template modeling, and ribosomal protein S6 kinase B1 (RPS6KB1) in the bone morphogenetic protein (BMP)/transforming growth factor β (TGF-β) pathway was screened out as the potential substrate of PPM1H by Rosetta. PPM1H could directly dephosphorylate p-RPS6KB1. To conclude, we discovered RPS6KB1 as a new PPM1H dephosphorylation substrate. PPM1H exhibited a suppressive effect on HCC progression by dephosphorylating p-RPS6KB1.
PubMed: 37456776
DOI: 10.1016/j.omtn.2023.06.013 -
Cell Division 2020Cell division is orchestrated by the phosphorylation and dephosphorylation of thousands of proteins. These post-translational modifications underlie the molecular... (Review)
Review
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.
PubMed: 32508972
DOI: 10.1186/s13008-020-00065-2 -
Molecular Cell Mar 2009The control of biological events requires strict regulation using complex protein phosphorylation and dephosphorylation strategies. The bulk of serine-threonine... (Review)
Review
The control of biological events requires strict regulation using complex protein phosphorylation and dephosphorylation strategies. The bulk of serine-threonine dephosphorylations are catalyzed by a handful of phosphatase catalytic subunits, giving rise to the misconception that these phosphatases are promiscuous and unregulated enzymes in vivo. The reality is much more nuanced: PP1 and PP2A, the most abundant serine-threonine phosphatases, are, in fact, families of hundreds of protein serine/threonine phosphatases, assembled from a few catalytic subunits in combination with a highly diverse array of regulators. As recent publications illustrate, these regulatory subunits confer specificity, selectivity, localization, and regulation on these important enzymes.
Topics: Animals; Catalytic Domain; Humans; Intracellular Signaling Peptides and Proteins; Isoenzymes; Models, Molecular; Phosphoprotein Phosphatases; Phosphorylation; Protein Conformation; Protein Phosphatase 1; Protein Phosphatase 2; Protein Processing, Post-Translational; Signal Transduction; Substrate Specificity; Transforming Growth Factor beta; tau Proteins
PubMed: 19285938
DOI: 10.1016/j.molcel.2009.02.015 -
Cell & Bioscience 2019Dual-specificity phosphatases (DUSPs) are a subset of protein tyrosine phosphatases (PTPs), many of which dephosphorylate the residues of phosphor-serine/threonine and... (Review)
Review
Dual-specificity phosphatases (DUSPs) are a subset of protein tyrosine phosphatases (PTPs), many of which dephosphorylate the residues of phosphor-serine/threonine and phosphor-tyrosine on mitogen-activated protein kinases (MAPKs), and hence are also referred to as MAPK phosphatases (MKPs). Homologue of Vaccinia virus H1 phosphatase gene clone 5 (HVH-5), also known as DUSP8, is a unique member of the DUSPs family of phosphatases. Accumulating evidence has shown that DUSP8 plays an important role in phosphorylation-mediated signal transduction of MAPK signaling ranging from cell oxidative stress response, cell apoptosis and various human diseases. It is generally believed that DUSP8 exhibits significant dephosphorylation activity against JNK, however, with the deepening of research, plenty of new literature reports that DUSP8 also has effective dephosphorylation activity on p38 MAPK and ERKs, successfully affects the transduction of MAPKs pathway, indicating that DUSP8 presents a unknown diversity of DUSPs family on distinct corresponding dephosphorylated substrates in different biological events. Therefore, the in-depth study of DUSP8 not only throws a new light on the multi-biological function of DUSPs, but also is much valuable for the reveal of complex pathobiology of clinical diseases. In this review, we provide a detail overview of DUSP8 phosphatase structure, biological function and expression regulation, as well as its role in related clinical human diseases, which might be help for the understanding of biological function of DUSP8 and the development of prevention, diagnosis and therapeutics in related human diseases.
PubMed: 31467668
DOI: 10.1186/s13578-019-0329-4