Protein phosphatase 2A has an essential role in promoting thymocyte survival during selection

The development of thymocytes to mature T cells in the thymus is tightly controlled by cellular selection, in which only a small fraction of thymocytes equipped with proper quality of TCRs progress to maturation. It is pivotal to protect the survival of the few T cells, which pass the selection. However, the signaling events, which safeguard the cell survival in thymus, are not totally understood. In this study, protein Ser/Thr phosphorylation in thymocytes undergoing positive selection is profiled by mass spectrometry. The results revealed large numbers of dephosphorylation changes upon T cell receptor (TCR) activation during positive selection. Subsequent substrate analysis pinpointed protein phosphatase 2A (PP2A) as the enzyme responsible for the dephosphorylation changes in developing thymocytes. PP2A catalytic subunit α (Ppp2ca) deletion in the T cell lineage in Ppp2caflox/flox-Lck-Cre mice (PP2A cKO) displayed dysregulated dephosphorylation of apoptosis-related proteins in double-positive (DP) cells and caused substantially decreased numbers of DP CD4+ CD8+ cells. Increased levels of apoptosis in PP2A cKO DP cells were found to underlie aberrant thymocyte development. Finally, the defective thymocyte development in PP2A cKO mice could be rescued by either Bcl2 transgene expression or by p53 knockout. In summary, our work reveals an essential role of PP2A in promoting thymocyte development through the regulation of cell survival.

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Itm2a Is Induced during Thymocyte Selection and T Cell Activation and Causes Downregulation of Cd8 When Overexpressed in Cd4+Cd8+ Double Positive Thymocytes

Journal of Experimental Medicine ◽

10.1084/jem.190.2.217 ◽

1999 ◽

Vol 190 (2) ◽

pp. 217-228 ◽

Cited By ~ 52

Author(s):

Jacqueline Kirchner ◽

Michael J. Bevan

Keyword(s):

T Cells ◽

T Cell ◽

Positive Selection ◽

T Cell Activation ◽

Antigen Processing ◽

Cell Activation ◽

Proximal Promoter ◽

Cell Surface Expression ◽

Thymocyte Development ◽

Double Positive

To identify novel genes that are involved in positive selection of thymocytes, we performed polymerase chain reaction (PCR)-based subtractive hybridization between selecting and nonselecting thymi. OT-1 T cell receptor (TCR) transgenic thymocytes on a recombination activating gene (RAG) null background are efficiently selected into the CD8 lineage in H-2b mice (RAG-2−/−OT-1, selecting thymi), but are not selected on a transporter associated with antigen processing (TAP) null background (RAG-2−/−TAP-1−/−OT-1, nonselecting thymi). We report here our studies of one gene, ITM2A, whose expression is dramatically higher in T cells in the selecting thymus. The expression pattern of ITM2A in thymocyte subsets correlates with upregulation during positive selection. In addition, ITM2A expression is higher in the thymus than in either the spleen or lymph nodes, but can be upregulated in peripheral T cells upon activation. ITM2A expression was also induced in RAG-2−/− thymocytes in vivo upon CD3 cross-linking. We demonstrate that ITM2A is a type II membrane glycoprotein that exists as two species with apparent Mr of 45 and 43 kD and appears to localize primarily to large cytoplasmic vesicles and the Golgi apparatus, but is also expressed on the cell surface. Expression on the surface of EL4 cells increases with activation by phorbol myristate acetate (PMA) and ionomycin. Finally, overexpression of ITM2A under control of the lck proximal promoter in mice results in partial downregulation of CD8 in CD4+CD8+ double positive (DP) thymocytes, and a corresponding increase in the number of CD4+CD8lo thymocytes. Possible roles for this novel activation marker in thymocyte development are discussed.

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Altered thymocyte and T cell development in neonatal mice with hyperoxia-induced lung injury

Journal of Perinatal Medicine ◽

10.1515/jpm-2016-0234 ◽

2018 ◽

Vol 46 (4) ◽

pp. 441-449

Author(s):

Sowmya Angusamy ◽

Tamer Mansour ◽

Mohammed Abdulmageed ◽

Rachel Han ◽

Brian C. Schutte ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Lung Injury ◽

T Cell Development ◽

Adaptive Immune System ◽

Cell Development ◽

Thymocyte Development ◽

Double Positive ◽

Neonatal Mice ◽

Single Positive

Abstract Background: The adaptive immune system of neonates is relatively underdeveloped. The thymus is an essential organ for adaptive T cell development and might be affected during the natural course of oxygen induced lung injury. The effect of prolonged hyperoxia on the thymus, thymocyte and T cell development, and its proliferation has not been studied extensively. Methods: Neonatal mice were exposed to 85% oxygen (hyperoxia) or room air (normoxia) up to 28 days. Flow cytometry using surface markers were used to assay for thymocyte development and proliferation. Results: Mice exposed to prolonged hyperoxia had evidence of lung injury associated alveolar simplification, a significantly lower mean weight, smaller thymic size, lower mean thymocyte count and higher percentage of apoptotic thymocytes. T cells subpopulation in the thymus showed a significant reduction in the count and proliferation of double positive and double negative T cells. There was a significant reduction in the count and proliferation of single positive CD4+ and CD8+ T cells. Conclusions: Prolonged hyperoxia in neonatal mice adversely affected thymic size, thymocyte count and altered the distribution of T cells sub-populations. These results are consistent with the hypothesis that prolonged hyperoxia causes defective development of T cells in the thymus.

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CD25 and Protein Phosphatase 2A Cooperate to Enhance IL-2R Signaling in Human Regulatory T Cells

The Journal of Immunology ◽

10.4049/jimmunol.1801570 ◽

2019 ◽

Vol 203 (1) ◽

pp. 93-104 ◽

Cited By ~ 4

Author(s):

Ying Ding ◽

Aixin Yu ◽

George C. Tsokos ◽

Thomas R. Malek

Keyword(s):

T Cells ◽

Regulatory T Cells ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Phosphatase 2A

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Promoter Hypomethylation Results in Increased Expression of Protein Phosphatase 2A in T Cells from Patients with Systemic Lupus Erythematosus

The Journal of Immunology ◽

10.4049/jimmunol.1000340 ◽

2011 ◽

Vol 186 (7) ◽

pp. 4508-4517 ◽

Cited By ~ 44

Author(s):

Katsue Sunahori ◽

Yuang-Taung Juang ◽

Vasileios C. Kyttaris ◽

George C. Tsokos

Keyword(s):

Systemic Lupus Erythematosus ◽

T Cells ◽

Lupus Erythematosus ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Systemic Lupus ◽

Phosphatase 2A

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Protein Phosphatase 2A Inactivates Bcl2’s Antiapoptotic Function by Dephosphorylation and Up-Regulation of Bcl2-p53 Binding.

Blood ◽

10.1182/blood.v108.11.1436.1436 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1436-1436

Author(s):

Xingming Deng ◽

Fengqin Gao ◽

Tammy Flagg ◽

W. Stratford May

Keyword(s):

Cell Death ◽

Cell Survival ◽

Okadaic Acid ◽

Protein Phosphatase ◽

Apoptotic Cell ◽

Protein Phosphatase 2A ◽

Survival Function ◽

Phosphorylation Site ◽

Apoptotic Cell Death ◽

Phosphatase 2A

Abstract DNA damage-induced p53/Bcl2 interaction at the outer mitochondrial membranes results in a Bcl2 conformational change and loss of its antiapoptotic function. Our data now indicate that either treatment of cells with the protein phosphatase 2A (PP2A) inhibitor, okadaic acid (10 nM), or specific disruption of PP2A activity by the expression of SV40 small tumor antigen enhances Bcl2 phosphorylation and suppresses the cisplatin-stimulated Bcl2-p53 interaction in association with prolonged cell survival. By contrast, C2-ceramide, a potent PP2A activator, reduces Bcl2 phosphorylation and increases Bcl2-p53 binding and promotes apoptotic cell death, suggesting that PP2A may function as a physiological regulator of Bcl2 by, at least in part, affecting its association with p53. Overexpression of the PP2A catalytic subunit (PP2A/C) suppresses Bcl2 phosphorylation in association with increased p53-Bcl2 binding and apoptotic cell death. By contrast, specific depletion of PP2A/C by RNA interference enhances Bcl2 phosphorylation, suppresses p53-Bcl2 interaction and prolongs cell survival. Purified PP2A can directly enhance the formation of the p53-Bcl2 complex in vitro in an okadaic acid-sensitive manner, supporting a direct mechanism. Importantly, PP2A directly interacts with Bcl2 at its BH4 domain which may function as the PP2A ‘docking site’ to potentially ‘bridge’ PP2A to the flexible loop domain which contains the physiological serine 70 phosphorylation site. Thus, PP2A may provide a double whammy to Bcl2’s survival function by both dephosphorylating and enhancing p53-Bcl2 binding. Therapeutically stimulating Bcl2 dephosphorylation and/or increasing Bcl2/p53 binding by activating PP2A may represent an efficient and novel antineoplastic approach.

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Protein Phosphatase 2A Isotypes Regulate Cell Surface Expression of the T Cell Receptor

Experimental and Clinical Immunogenetics ◽

10.1159/000049084 ◽

2001 ◽

Vol 18 (1) ◽

pp. 24-33 ◽

Cited By ~ 5

Author(s):

Jens Peter H. Lauritsen ◽

Charlotte Menné ◽

Jesper Kastrup ◽

Jes Dietrich ◽

Carsten Geisler

Keyword(s):

T Cell ◽

Cell Surface ◽

T Cell Receptor ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Cell Receptor ◽

Surface Expression ◽

Cell Surface Expression ◽

Phosphatase 2A

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Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A): Could It Be a Promising Biomarker and Therapeutic Target in Parkinson’s Disease?

Molecular Neurobiology ◽

10.1007/s12035-021-02670-w ◽

2022 ◽

Author(s):

Sijia Yin ◽

Chao Han ◽

Yun Xia ◽

Fang Wan ◽

Junjie Hu ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Protein Phosphatase ◽

Essential Role ◽

Protein Phosphatase 2A ◽

Area Under The Curve ◽

Alpha Synuclein ◽

Phosphatase 2A ◽

Induced Aggregation ◽

Age And Sex

AbstractParkinson’s disease (PD) is an incurable neurodegenerative disease characterized by aggregation of pathological alpha-synuclein (α-syn) and loss of dopaminergic neuron in the substantia nigra. Inhibition of phosphorylation of the α-syn has been shown to mediate alleviation of PD-related pathology. Protein phosphatase 2A (PP2A), an important serine/threonine phosphatase, plays an essential role in catalyzing dephosphorylation of the α-syn. Here, we identified and validated cancerous inhibitor of PP2A (CIP2A), as a potential diagnostic biomarker for PD. Our data showed that plasma CIP2A concentrations in PD patients were significantly lower compared to age- and sex-matched controls, 1.721 (1.435–2.428) ng/ml vs 3.051(2.36–5.475) ng/ml, p < 0.0001. The area under the curve of the plasma CIP2A in distinguishing PD from the age- and sex-matched controls was 0.776. In addition, we evaluated the role of CIP2A in PD-related pathogenesis in PD cellular and MPTP-induced mouse model. The results demonstrated that CIP2A is upregulated in PD cellular and MPTP-induced mouse models. Besides, suppression of the CIP2A expression alleviates rotenone induced aggregation of the α-syn as well as phosphorylation of the α-syn in SH-SY5Y cells, which is associated with increased PP2A activity. Taken together, our data demonstrated that CIP2A plays an essential role in the mechanisms related to PD development and might be a novel PD biomarker.

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Chromatin organizer SATB1 controls the cell identity of CD4+ CD8+ double-positive thymocytes by compacting super-enhancers

10.21203/rs.3.rs-1069634/v1 ◽

2021 ◽

Author(s):

Delong Feng ◽

Yanhong Chen ◽

Ranran Dai ◽

Shasha Bian ◽

Wei Xue ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Receptor Gene ◽

Cell Receptor ◽

Regulation Mechanism ◽

Thymocyte Development ◽

Double Positive ◽

Enhancer Activity ◽

Cell Identity ◽

Single Positive

Abstract CD4+ and CD8+ double-positive (DP) thymocytes are at a crucial stage during the T cell development in the thymus. DP cells rearrange the T cell receptor gene Tcra to generate T cell receptors with TCRβ. Then DP cells differentiate into CD4 or CD8 single-positive (SP) thymocytes, Regulatory T cells, or invariant nature kill T cells (iNKT) according to the TCR signal. Chromatin organizer SATB1 is highly expressed in DP cells and plays an essential role in regulating Tcra rearrangement and differentiation of DP cells. Here we explored the mechanism of SATB1 orchestrating gene expression in DP cells. Single-cell RNA sequencing assay of SATB1-deficient thymocytes showed that the cell identity of DP thymocytes was changed, and the genes specifically highly expressed in DP cells were down-regulated. The super-enhancers regulate the expressions of the DP-specific genes, and the SATB1 deficiency reduced the super-enhancer activity. Hi-C data showed that interactions in super-enhancers and between super-enhancers and promoters decreased in SATB1 deficient thymocytes. We further explored the regulation mechanism of two SATB1-regulating genes, Ets2 and Bcl6, in DP cells and found that the knockout of the super-enhancers of these two genes impaired the development of DP cells. Our research reveals that SATB1 globally regulates super-enhancers of DP cells and promotes the establishment of DP cell identity, which helps understand the role of SATB1 in thymocyte development.

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