Circumventing Cellular Control of PP2A by Methylation Promotes Transformation in an Akt-Dependent Manner

Jackson, Jennifer; Pallas, David C.

doi:10.1593/neo.12768

Cited by 55 publications

(82 citation statements)

References 70 publications

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“…Methylation Assay-Methylation assays for PP4c and PP6c were performed as previously reported for PP2A (19,56). Briefly, two 20-l aliquots of each cell lysate were prepared.…”

Section: Methodsmentioning

confidence: 99%

“…HDAC3 has been implicated in cancer (53)(54)(55). Recently, it has been shown that LCMT-1 KD promotes cancer phenotypes such as anchorage-independent growth (56). It would be interesting to determine if dysregulation of HDAC3 contributes to the anchorage-independent growth phenotype in LCMT-1 KD cells.…”

Section: Lcmt-1 Differentially Regulates Different Pp4 Holoenzymesmentioning

confidence: 99%

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Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes

Hwang

Lee²,

Pallas

2016

Journal of Biological Chemistry

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The protein phosphatase 2A (PP2A) subfamily of phosphatases, PP2A, PP4, and PP6, are multifunctional serine/threonine protein phosphatases involved in many cellular processes. Carboxyl methylation of the PP2A catalytic subunit (PP2Ac) C-terminal leucine is regulated by the opposing activities of leucine carboxyl methyltransferase 1 (LCMT-1) and protein phosphatase methylesterase 1 (PME-1) and regulates PP2A holoenzyme formation. The site of methylation on PP2Ac is conserved in the catalytic subunits of PP4 and PP6, and PP4 is also methylated on that site, but the identities of the methyltransferase enzyme for PP4 are not known. Whether PP6 is methylated is also not known. Here we use antibodies specific for the unmethylated phosphatases to show that PP6 is carboxyl-methylated and that LCMT-1 is the major methyltransferase for PP2A, PP4, and PP6 in mouse embryonic fibroblasts (MEFs). Analysis of PP2A and PP4 complexes by blue native polyacrylamide gel electrophoresis (BN-PAGE) indicates that PP4 holoenzyme complexes, like those of PP2A, are differentially regulated by LCMT-1, with the PP4 regulatory subunit 1 (PP4R1)-containing PP4 complex being the most dramatically affected by the LCMT-1 loss. MEFs derived from LCMT-1 knock-out mouse embryos have reduced levels of PP2A B regulatory subunit and PP4R1 relative to control MEFs, indicating that LCMT-1 is important for maintaining normal levels of these subunits. Finally, LCMT-1 homozygous knock-out MEFs exhibited hyperphosphorylation of HDAC3, a reported target of the methylation-dependent PP4R1-PP4c complex. Collectively, our data suggest that LCMT-1 coordinately regulates the carboxyl methylation of PP2A-related phosphatases and, consequently, their holoenzyme assembly and function.

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“…Methylation Assay-Methylation assays for PP4c and PP6c were performed as previously reported for PP2A (19,56). Briefly, two 20-l aliquots of each cell lysate were prepared.…”

Section: Methodsmentioning

confidence: 99%

Section: Lcmt-1 Differentially Regulates Different Pp4 Holoenzymesmentioning

confidence: 99%

Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes

Hwang

Lee²,

Pallas

2016

Journal of Biological Chemistry

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“…In addition, MAPK3 (ERK1) and AKT1 were included in the RRP library as internal controls representing known PME-1 effector proteins (11,23). The relevance of the PC-3 cell model for assessing PME-1 interactome function was validated by robust inhibition of colony growth by PME-1 depletion ( Supplemental Fig.…”

Section: Rrp Analysis Of Pin1mentioning

confidence: 99%

“…5F), further indicating its potential involvement in cancer biology. were included to RRP analysis as previously validated PME-1 effector genes (11,23). FunCoup similarity index (min.…”

Section: Rrp Analysis Of Pin1mentioning

confidence: 99%

Relevance Rank Platform (RRP) for Functional Filtering of High Content Protein–Protein Interaction Data*

Pokharel

Saarela

Szwajda

et al. 2015

Molecular & Cellular Proteomics

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High content protein interaction screens have revolutionized our understanding of protein complex assembly. However, one of the major challenges in translation of high content protein interaction data is identification of those interactions that are functionally relevant for a particular biological question. To address this challenge, we developed a relevance ranking platform (RRP), which consist of modular functional and bioinformatic filters to provide relevance rank among the interactome proteins. We demonstrate the versatility of RRP to enable a systematic prioritization of the most relevant interaction partners from high content data, highlighted by the analysis of cancer relevant protein interactions for oncoproteins Pin1 and PME-1. We validated the importance of selected interactions by demonstration of PTOV1 and CSKN2B as novel regulators of Pin1 target c-Jun phosphorylation and reveal previously unknown interacting proteins that may mediate PME-1 effects via PP2A-inhibition. The RRP framework is modular and can be modified to answer versatile research problems depending on the nature of the biological question under study. Based on comparison of RRP to other existing filtering tools, the presented data indicate that RRP offers added value especially for the analysis of interacting proteins for which there is no sufficient prior knowledge available. Finally, we encourage the use of RRP in combination with either SAINT or CRAPome computational tools for selecting the candidate interactors that fulfill the both important requirements, functional relevance, and high confidence interaction detection. Molecular & Cellular

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“…Specific heterotrimers dephosphorylate and stabilize tumor suppressors, such as p53 (5,6) and p107 (7); thus, PP2A activity is important in cell-cycle regulation and tumor suppression. PP2A has been shown to dephosphorylate positive regulators of cell signaling pathways such as ERK and Akt (8)(9)(10)(11), inhibiting them and promoting senescence or apoptosis. Inhibition of PP2A promotes enhanced cell proliferation, impairment of cell differentiation, malignant cell transformation (reviewed in refs.…”

Section: Introductionmentioning

confidence: 99%

PME-1 Modulates Protein Phosphatase 2A Activity to Promote the Malignant Phenotype of Endometrial Cancer Cells

et al. 2014

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Protein phosphatase 2A (PP2A) negatively regulates tumorigenic signaling pathways, in part, by supporting the function of tumor suppressors like p53. The PP2A methylesterase PME-1 limits the activity of PP2A by demethylating its catalytic subunit. Here, we report the finding that PME-1 overexpression correlates with increased cell proliferation and invasive phenotypes in endometrial adenocarcinoma cells, where it helps maintain activated ERK and Akt by inhibiting PP2A. We obtained evidence that PME-1 could bind and regulate protein phosphatase 4 (PP4), a tumor-promoting protein, but not the related protein phosphatase 6 (PP6). When the PP2A, PP4, or PP6 catalytic subunits were overexpressed, inhibiting PME-1 was sufficient to limit cell proliferation. In clinical specimens of endometrial adenocarcinoma, PME-1 levels were increased and we found that PME-1 overexpression was sufficient to drive tumor growth in a xenograft model of the disease. Our findings identify PME-1 as a modifier of malignant development and suggest its candidacy as a diagnostic marker and as a therapeutic target in endometrial cancer. Cancer Res; 74(16); 4295-305. Ó2014 AACR.

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Circumventing Cellular Control of PP2A by Methylation Promotes Transformation in an Akt-Dependent Manner

Cited by 55 publications

References 70 publications

Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes

Leucine Carboxyl Methyltransferase 1 (LCMT-1) Methylates Protein Phosphatase 4 (PP4) and Protein Phosphatase 6 (PP6) and Differentially Regulates the Stable Formation of Different PP4 Holoenzymes

Relevance Rank Platform (RRP) for Functional Filtering of High Content Protein–Protein Interaction Data*

PME-1 Modulates Protein Phosphatase 2A Activity to Promote the Malignant Phenotype of Endometrial Cancer Cells

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