CMyBPC_dephosphorylation_PP1_PP2A
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Enriched phosphopeptides were loaded onto a 50 cm EN C18 PepMap column with elution over a 1 h acquisition driven by a Waters mClass nanoUPLC. Eluted peptides were measured using a Thermo Orbitrap Fusion Tribrid mass spectrometer, with MS spectra acquired in the Orbitrap and MS2 spectra acquired in parallel, following HCD fragmentation, in the linear ion trap.
ORGANISM(S): Rattus Norvegicus (ncbitaxon:10116)
SUBMITTER: 
Daniel Koch
PROVIDER: MSV000091995 | MassIVE | Fri May 19 15:23:00 BST 2023
REPOSITORIES: MassIVE
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Project description:The PP2A phosphatase is often inactivated in cancer and is considered as a tumour suppressor. A new pathway controlling PP2A activity in mitosis has been recently described. This pathway includes the Greatwall (GWL) kinase and its substrates endosulfines. At mitotic entry, GWL is activated and phosphorylates endosulfines that then bind and inhibit PP2A. We analysed whether GWL overexpression could participate in cancer development. We show that GWL overexpression promotes cell transformation and increases invasive capacities of cells through hyperphosphorylation of the oncogenic kinase AKT. Interestingly, AKT hyperphosphorylation induced by GWL is independent of endosulfines. Rather, GWL induces GSK3 kinase dephosphorylation in its inhibitory sites and subsequent SCF-dependent degradation of the PHLPP phosphatase responsible for AKT dephosphorylation. In line with its oncogenic activity, we find that GWL is often overexpressed in human colorectal tumoral tissues. Thus, GWL is a human oncoprotein that promotes the hyperactivation of AKT via the degradation of its phosphatase, PHLPP, in human malignancies.
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Project description:BACKGROUND: Corticosteroid insensitivity is a major barrier of treatment for some chronic inflammatory diseases, such as severe asthma, but the molecular mechanism of the insensitivity has not been fully elucidated. The object of this study is to investigate the role of protein phosphate 2A (PP2A), a serine/threonine phosphatase, on corticosteroid sensitivity in severe asthma. METHODOLOGY/PRINCIPAL FINDINGS: Corticosteroid sensitivity was determined by the dexamethasone ability to inhibit TNF?-induced IL-8 or LPS-induced TNF? production. PP2A expression, glucocorticoid receptor (GR) nuclear translocation defined as the nuclear/cytoplasmic GR ratio and phosphorylation of GR-Ser²²?, c-Jun N-terminal kinase 1 (JNK1) and PP2A were analysed by Western-blotting. Phosphatase activity was measured by fluorescence-based assay. Okadaic acid (OA), a PP2A inhibitor, reduced corticosteroid sensitivity with reduced GR nuclear translocation and increased GR phosphorylation in U937 monocytic cells. PP2A knockdown by RNA interference showed similar effects. IL-2/IL-4 treatment to U937 reduced corticosteroid sensitivity, and PP2A expression/activity. In peripheral blood mononuclear cells (PBMCs) from severe asthma, the PP2A expression and activity were significantly reduced with concomitant enhancement of PP2A(C)-Tyr³?? phosphorylation compared with those in healthy volunteers. As the results, GR-Ser²²? and JNK1 phosphorylation were increased. The expression and activity of PP2A were negatively correlated with phosphorylation levels of GR-Ser²²?. Furthermore, co-immunoprecipitation assay in U937 cells revealed that PP2A associated with GR and JNK1 and IL-2/IL-4 exposure caused dissociation of each molecule. Lastly, PP2A overexpression increased corticosteroid sensitivity in U937 cells. CONCLUSIONS/SIGNIFICANCE: PP2A regulates GR nuclear translocation and corticosteroid sensitivity possibly by dephosphorylation of GR-Ser²²? via dephosphorylation of upstream JNK1. This novel mechanism will provide new insight for the development of new therapy for severe asthma.
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Project description:PP2A is an essential protein phosphatase that regulates most cellular processes through the formation of holoenzymes containing distinct regulatory B-subunits. Only a limited number of PP2A-regulated phosphorylation sites are known. This hampers our understanding of the mechanisms of site-specific dephosphorylation and of its tumor suppressor functions. Here, we develop phosphoproteomic strategies for global substrate identification of PP2A-B56 and PP2A-B55 holoenzymes. Strikingly, we find that B-subunits directly affect the dephosphorylation site preference of the PP2A catalytic subunit, resulting in unique patterns of kinase opposition. For PP2A-B56, these patterns are further modulated by affinity and position of B56 binding motifs. Our screens identify phosphorylation sites in the cancer target ADAM17 that are regulated through a conserved B56 binding site. Binding of PP2A-B56 to ADAM17 protease decreases growth factor signaling and tumor development in mice. This work provides a roadmap for the identification of phosphatase substrates, and reveals unexpected mechanisms governing PP2A dephosphorylation-site specificity and tumor suppressor function.
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Project description:Analysis performed on protein samples submitted by Zhe Hu of the John E. Cronan Laboratory by the Protein Sciences Facility of the Biotechnology Center of the University of Illinois at Urbana-Champaign
2021-01-29 | PXD023486 | Pride