PP2A/B55α substrate recruitment as defined by the retinoblastoma-related protein p107

Protein phosphorylation is a reversible post-translation modification essential in cell signaling. This study addresses a long-standing question as to how the most abundant serine/threonine Protein Phosphatase 2 (PP2A) holoenzyme, PP2A/B55α, specifically recognizes substrates and presents them to the enzyme active site. Here, we show how the PP2A regulatory subunit B55α recruits p107, a pRB-related tumor suppressor and B55α substrate. Using molecular and cellular approaches, we identified a conserved region 1 (R1, residues 615-626) encompassing the strongest p107 binding site. This enabled us to identify an 'HxRVxxV619-625' short linear motif (SLiM) in p107 as necessary for B55α binding and dephosphorylation of the proximal pSer-615 in vitro and in cells. Numerous B55α/PP2A substrates, including TAU, contain a related SLiM C-terminal from a proximal phosphosite, 'p[ST]-P-x(4,10)-[RK]-V-x-x-[VI]-R'. Mutation of conserved SLiM residues in TAU dramatically inhibits dephosphorylation by PP2A/B55α, validating its generality. A data-guided computational model details the interaction of residues from the conserved p107 SLiM, the B55α groove, and phosphosite presentation. Altogether these data provide key insights into PP2A/B55α mechanisms of substrate recruitment and active site engagement, and also facilitate identification and validation of new substrates, a key step towards understanding PP2A/B55α role in multiple cellular processes.

Download Full-text

PP2A/B55α substrate recruitment as defined by the retinoblastoma-related protein p107

10.1101/2021.03.02.433577 ◽

2021 ◽

Author(s):

Holly Fowle ◽

Ziran Zhao ◽

Qifang Xu ◽

Xinru Wang ◽

Mary Adeyemi ◽

...

Keyword(s):

Active Site ◽

Protein Phosphatase ◽

Regulatory Subunit ◽

Related Protein ◽

Linear Motif ◽

Enzyme Active Site ◽

Cellular Processes ◽

Protein Phosphatase 2 ◽

Standing Question

AbstractProtein phosphorylation is a reversible post-translation modification essential in cell signaling. This study addresses a long-standing question as to how the most abundant serine/threonine Protein Phosphatase 2 (PP2A) holoenzyme, PP2A/B55α, specifically recognizes substrates and presents them to the enzyme active site. Here, we show how the PP2A regulatory subunit B55α recruits p107, a pRB-related tumor suppressor and B55α substrate. Using molecular and cellular approaches, we identified a conserved region 1 (R1, residues 615-626) encompassing the strongest p107 binding site. This enabled us to identify an “HxRVxxV619-625” short linear motif (SLiM) in p107 as necessary for B55α binding and dephosphorylation of the proximal pSer-615 in vitro and in cells. Numerous B55α/PP2A substrates, including TAU, contain a related SLiM C-terminal from a proximal phosphosite, “p[ST]-P-x(5-10)-[RK]-V-x-x-[VI]-R”. Mutation of conserved SLiM residues in TAU dramatically inhibits dephosphorylation by PP2A/B55α, validating its generality. A data-guided computational model details the interaction of residues from the conserved p107 SLiM, the B55α groove, and phosphosite presentation. Altogether these data provide key insights into PP2A/B55α mechanisms of substrate recruitment and active site engagement, and also facilitate identification and validation of new substrates, a key step towards understanding PP2A/B55〈 role in multiple cellular processes.

Download Full-text

Conformation-Specific Inhibitory Anti-MMP-7 Monoclonal Antibody Sensitizes Pancreatic Ductal Adenocarcinoma Cells to Chemotherapeutic Cell Kill

Cancers ◽

10.3390/cancers13071679 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1679

Author(s):

Vishnu Mohan ◽

Jean P. Gaffney ◽

Inna Solomonov ◽

Maxim Levin ◽

Mordehay Klepfish ◽

...

Keyword(s):

Monoclonal Antibody ◽

Active Site ◽

Drug Targets ◽

Fas Ligand ◽

Specific Activity ◽

Matrix Metalloproteases ◽

Ductal Adenocarcinoma ◽

Enzyme Active Site ◽

Induced Apoptosis

Matrix metalloproteases (MMPs) undergo post-translational modifications including pro-domain shedding. The activated forms of these enzymes are effective drug targets, but generating potent biological inhibitors against them remains challenging. We report the generation of anti-MMP-7 inhibitory monoclonal antibody (GSM-192), using an alternating immunization strategy with an active site mimicry antigen and the activated enzyme. Our protocol yielded highly selective anti-MMP-7 monoclonal antibody, which specifically inhibits MMP-7′s enzyme activity with high affinity (IC50 = 132 ± 10 nM). The atomic model of the MMP-7-GSM-192 Fab complex exhibited antibody binding to unique epitopes at the rim of the enzyme active site, sterically preventing entry of substrates into the catalytic cleft. In human PDAC biopsies, tissue staining with GSM-192 showed characteristic spatial distribution of activated MMP-7. Treatment with GSM-192 in vitro induced apoptosis via stabilization of cell surface Fas ligand and retarded cell migration. Co-treatment with GSM-192 and chemotherapeutics, gemcitabine and oxaliplatin elicited a synergistic effect. Our data illustrate the advantage of precisely targeting catalytic MMP-7 mediated disease specific activity.

Download Full-text

Abstract 70: Protein Phosphatase 1 Contributes to Atrial Stunning in Atrial Fibrillation

Circulation Research ◽

10.1161/res.121.suppl_1.70 ◽

2017 ◽

Vol 121 (suppl_1) ◽

Author(s):

Srikanth Perike ◽

Xander Wehrens ◽

Dawood Darbar ◽

Mark McCauley

Keyword(s):

Atrial Fibrillation ◽

Light Chain ◽

Protein Phosphatase ◽

Myosin Light Chain ◽

Stroke Risk ◽

Protein Phosphatase 1 ◽

Regulatory Subunit ◽

Future Studies ◽

Hek Cells

Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia, and increases a patient’s stroke risk five-fold. Reduced atrial contractility (stunning) is observed in AF and contributes to stroke risk; however, the mechanisms responsible for atrial stunning in AF are unknown. Recent data from our laboratory indicate that protein phosphatase 1 (PP1) dephosphorylation of myosin light chain 2a (MLC2a) may contribute to atrial stunning in AF. Objective: To determine how the PP1 regulatory subunit 12C (PPP1R12C) and catalytic (PPP1c) subunits modify atrial sarcomere phosphorylation in AF. Methods: We evaluated the protein expression, binding and phosphorylation among PPP1R12C, PPP1c, and MLC2a in transfected HL-1 cells, murine atrial tissue (Pitx2null +/– mice, with a genetic predisposition AF), and in HEK cells. An inhibitor of PPP1R12C phosphorylation, BDP5290, was used to enhance the PPP1R12C-PPP1C interaction. Results: In Pitx2 null +/– mice, PPP1R12C was increased by 2-fold ( P <0.01) and associated with a 40% reduction in S-19-MLC2a phosphorylation versus WT mice ( P <0.058). BDP5290 increased PPP1R12C-PPP1C binding by >3-fold in HL-1 cells ( P <0.01). BDP5290 reduced MLC2a phosphorylation by 40% through an enhanced interaction with PPP1R12C by >3-fold in HEK cells ( P <0.01). Conclusion: In Pitx2 null+/- mice, increased expression of PPP1R12C is associated with PP1 holoenzyme targeting to sarcomeric MLC2a, and is associated with reduced S19-MLC2a phosphorylation. Additionally, BDP5290 enhances the PPP1R12C-PPP1C interaction and models PP1 activity in AF. Future studies will examine the effects of both AF and BDP5290 upon atrial contractility in vitro.

Download Full-text

Systematic analysis and integrative discovery of active-site subpocket-specific dehydroquinate synthase inhibitors combating antibiotic-resistant Staphylococcus aureus infection

Journal of Bioinformatics and Computational Biology ◽

10.1142/s0219720018500270 ◽

2018 ◽

Vol 16 (06) ◽

pp. 1850027

Author(s):

Quanfeng Liu ◽

Liping Li ◽

Fei Xu

Keyword(s):

Staphylococcus Aureus ◽

Active Site ◽

Shikimate Pathway ◽

In Vitro Susceptibility ◽

Systematic Analysis ◽

Antibiotic Resistant ◽

Enzyme Active Site ◽

Specific Inhibitors ◽

Dehydroquinate Synthase

Shikimate pathway plays an essential role in the biosynthesis of aromatic amino acids in various plants and bacteria, which consists of seven key enzymes and they are all attractive targets for antibacterial agent development due to their absence in humans. The Staphylococcus aureus dehydroquinate synthase (SaDHQS) is involved in the second step of shikimate pathway, which catalyzes the NAD[Formula: see text]-dependent conversion of 3-deoxy-D-arabino-heptulosonate-7-phosphate to dehydroquinate via multiple steps. The enzyme active site can be characterized by two spatially separated subpockets 1 and 2, which represent the reaction center of substrate adduct with NAD[Formula: see text] nicotinamide moiety and the assistant binding site of NAD[Formula: see text] adenine moiety, respectively. In silico virtual screening is performed against a biogenic compound library to discover SaDHQS subpocket-specific inhibitors, which were then tested against both antibiotic-sensitive and antibiotic-resistant S. aureus strains by using in vitro susceptibility test. The activity profile of hit compounds has no considerable difference between the antibiotic-sensitive and -resistant strains. The subpocket 1-specific inhibitors exhibit a generally higher activity than subpocket 2-specific inhibitors, and they also hold a strong selectivity between their cognate and noncognate subpockets. Dynamics and energetics analyses reveal that the SaDHQS active site prefers to interact with amphipathic and polar inhibitors by forming multiple hydrogen bonds and van der Waals packing at the complex interfaces of the two subpockets with their cognate inhibitors.

Download Full-text

The split protein phosphatase system

Biochemical Journal ◽

10.1042/bcj20170726 ◽

2018 ◽

Vol 475 (23) ◽

pp. 3707-3723 ◽

Cited By ~ 9

Author(s):

Anne Bertolotti

Keyword(s):

Protein Phosphatase ◽

Catalytic Subunit ◽

Regulatory Subunit ◽

Post Translational Modification ◽

Antagonistic Action ◽

Cellular Processes ◽

Depth Study ◽

Split Protein ◽

Phosphatase System ◽

Physiological Substrates

Reversible phosphorylation of proteins is a post-translational modification that regulates all aspect of life through the antagonistic action of kinases and phosphatases. Protein kinases are well characterized, but protein phosphatases have been relatively neglected. Protein phosphatase 1 (PP1) catalyzes the dephosphorylation of a major fraction of phospho-serines and phospho-threonines in cells and thereby controls a broad range of cellular processes. In this review, I will discuss how phosphatases were discovered, how the view that they were unselective emerged and how recent findings have revealed their exquisite selectivity. Unlike kinases, PP1 phosphatases are obligatory heteromers composed of a catalytic subunit bound to one (or two) non-catalytic subunit(s). Based on an in-depth study of two holophosphatases, I propose the following: selective dephosphorylation depends on the assembly of two components, the catalytic subunit and the non-catalytic subunit, which serves as a high-affinity substrate receptor. Because functional complementation of the two modules is required to produce a selective holophosphatase, one can consider that they are split enzymes. The non-catalytic subunit was often referred to as a regulatory subunit, but it is, in fact, an essential component of the holoenzyme. In this model, a phosphatase and its array of mostly orphan substrate receptors constitute the split protein phosphatase system. The set of potentially generalizable principles outlined in this review may facilitate the study of these poorly understood enzymes and the identification of their physiological substrates.

Download Full-text

MEF2A Regulates the MEG3-DIO3 miRNA Mega Cluster-Targeted PP2A Signaling in Bovine Skeletal Myoblast Differentiation

International Journal of Molecular Sciences ◽

10.3390/ijms20112748 ◽

2019 ◽

Vol 20 (11) ◽

pp. 2748 ◽

Cited By ~ 3

Author(s):

Yaning Wang ◽

Chugang Mei ◽

Xiaotong Su ◽

Hongbao Wang ◽

Wucai Yang ◽

...

Keyword(s):

Protein Phosphatase ◽

Molecular Mechanisms ◽

Regulatory Subunit ◽

Myoblast Differentiation ◽

Mirna Cluster ◽

Skeletal Myoblast ◽

Iodothyronine Deiodinase ◽

Luciferase Activity Assay ◽

Phosphatase 2A ◽

Protein Phosphatase 2

Understanding the molecular mechanisms of skeletal myoblast differentiation is essential for studying muscle developmental biology. In our previous study, we reported that knockdown of myocyte enhancer factor 2A (MEF2A) inhibited myoblast differentiation. Here in this study, we further identified that MEF2A controlled this process through regulating the maternally expressed 3 (MEG3)—iodothyronine deiodinase 3 (DIO3) miRNA mega cluster and protein phosphatase 2A (PP2A) signaling. MEF2A was sufficient to induce MEG3 expression in bovine skeletal myoblasts. A subset of miRNAs in the MEG3-DIO3 miRNA cluster was predicted to target PP2A subunit genes. Consistent with these observations, MEF2A regulated PP2A signaling through its subunit gene protein phosphatase 2 regulatory subunit B, gamma (PPP2R2C) during bovine myoblast differentiation. MiR-758 and miR-543 in the MEG3-DIO3 miRNA cluster were down-regulated in MEF2A-depleted myocytes. Expression of miR-758 and miR-543 promoted myoblast differentiation and repressed PPP2R2C expression. Luciferase activity assay showed that PPP2R2C was post-transcriptionally targeted by miR-758 and miR-543. Taken together, these results reveal that the MEG3-DIO3 miRNAs function at downstream of MEF2A to modulate PP2A signaling in bovine myoblast differentiation.

Download Full-text

Loss of a Protein Phosphatase 2A Regulatory Subunit (Cdc55p) Elicits Improper Regulation of Swe1p Degradation

Molecular and Cellular Biology ◽

10.1128/mcb.20.21.8143-8156.2000 ◽

2000 ◽

Vol 20 (21) ◽

pp. 8143-8156 ◽

Cited By ~ 37

Author(s):

Haifeng Yang ◽

Wei Jiang ◽

Matthew Gentry ◽

Richard L. Hallberg

Keyword(s):

Phosphatase Activity ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Cell Types ◽

Regulatory Subunit ◽

Cyclin Dependent Kinase ◽

Wild Type ◽

Phosphatase 2A

ABSTRACT CDC55 encodes a Saccharomyces cerevisiaeprotein phosphatase 2A (PP2A) regulatory subunit.cdc55-null cells growing at low temperature exhibit a failure of cytokinesis and produce abnormally elongated buds, butcdc55-null cells producing the cyclin-dependent kinase Cdc28-Y19F, which is unable to be inhibited by Y19 phosphorylation, show a loss of the abnormal morphology. Furthermore,cdc55-null cells exhibit a hyperphosphorylation of Y19. For these reasons, we have examined in wild-type and cdc55-null cells the levels and activities of the kinase (Swe1p) and phosphatase (Mih1p) that normally regulate the extent of Cdc28 Y19 phosphorylation. We find that Mih1p levels are comparable in the two strains, and an estimate of the in vivo and in vitro phosphatase activity of this enzyme in the two cell types indicates no marked differences. By contrast, while Swe1p levels are similar in unsynchronized and S-phase-arrested wild-type and cdc55-null cells, Swe1 kinase is found at elevated levels in mitosis-arrestedcdc55-null cells. This excess Swe1p incdc55-null cells is the result of ectopic stabilization of this protein during G2 and M, thereby accounting for the accumulation of Swe1p in mitosis-arrested cells. We also present evidence indicating that, in cdc55-null cells, misregulated PP2A phosphatase activity is the cause of both the ectopic stabilization of Swe1p and the production of the morphologically abnormal phenotype.

Download Full-text

Protein phosphatase type 1 interacts with proteins required for meiosis and other cellular processes in Saccharomyces cerevisiae.

Molecular and Cellular Biology ◽

10.1128/mcb.16.8.4199 ◽

1996 ◽

Vol 16 (8) ◽

pp. 4199-4206 ◽

Cited By ~ 67

Author(s):

J Tu ◽

W Song ◽

M Carlson

Keyword(s):

Saccharomyces Cerevisiae ◽

Hybrid System ◽

Protein Phosphatase ◽

Regulatory Subunit ◽

Specific Substrate ◽

Type I ◽

Cellular Processes ◽

Cell Extracts ◽

Two Hybrid ◽

Protein Phosphatase Type

Protein phosphatase type I (PP1) is involved in diverse cellular processes, and its activity toward specific substrates is thought to be controlled by different regulatory or targeting subunits. To identify regulatory subunits and substrates of the Saccharomyces cerevisiae PP1, encoded by GLC7, we used the two-hybrid system to detect interacting proteins. Among the many proteins identified were Gac1, a known glycogen regulatory subunit, and a protein with homology to Gac1. We also characterized a new gene designated GIP1, for Glc7-interacting protein. We show that a Gip1 fusion protein coimmunoprecipitates with PP1 from cell extracts. Molecular and genetic analyses indicate that GIP1 is expressed specifically during meiosis, affects transcription of late meiotic genes, and is essential for sporulation. Thus, the Gip1 protein is a candidate for a meiosis-specific substrate or regulator of PP1. Finally, we recovered two genes, RED1 and SCD5, with roles in meiosis and the vesicular secretory pathway, respectively. These results provide strong evidence implicating PP1 function in meiosis. In addition, this study indicates that the two-hybrid system offers a promising approach to understanding the multiple roles and interactions of PP1 in cellular regulation.

Download Full-text