Cross-talk between Serine/Threonine Protein Phosphatase 2A and Protein Tyrosine Phosphatase 1B Regulates Src Activation and Adhesion of Integrin αIIbβ3to Fibrinogen

GSK-3β (glycogen synthase kinase-3β), a crucial tau kinase, negatively regulates PP2A (protein phosphatase 2A), the most active tau phosphatase that is suppressed in the brain in AD (Alzheimer's disease). However, the molecular mechanism is not understood. In the present study we found that activation of GSK-3β stimulates the inhibitory phosphorylation of PP2A at Tyr307 (pY307-PP2A), whereas inhibition of GSK-3β decreased the level of pY307-PP2A both in vitro and in vivo. GSK-3β is a serine/threonine kinase that can not phosphorylate tyrosine directly, therefore we measured PTP1B (protein tyrosine phosphatase 1B) and Src (a tyrosine kinase) activities. We found that GSK-3β can modulate both PTP1B and Src protein levels, but it only inhibits PTP1B activity, with no effect on Src. Furthermore, only knockdown of PTP1B but not Src by siRNA (small interfering RNA) eliminates the effects of GSK-3β on PP2A. GSK-3β phosphorylates PTP1B at serine residues, and activation of GSK-3β reduces the mRNA level of PTP1B. Additionally, we also observed that GSK-3 negatively regulates the protein and mRNA levels of PP2A, and knockdown of CREB (cAMP-response-element-binding protein) abolishes the increase in PP2A induced by GSK-3 inhibition. The results of the present study suggest that GSK-3β inhibits PP2A by increasing the inhibitory Tyr307 phosphorylation and decreasing the expression of PP2A, and the mechanism involves inhibition of PTP1B and CREB.

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Role of protein tyrosine phosphatase 1B (PTP1B) in the increased sensitivity of endothelial cells to a promigratory effect of erythropoietin in an inflammatory environment

Biological Chemistry ◽

10.1515/hsz-2020-0136 ◽

2020 ◽

Vol 401 (10) ◽

pp. 1167-1180

Author(s):

María Eugenia Chamorro ◽

Romina Maltaneri ◽

Agustina Schiappacasse ◽

Alcira Nesse ◽

Daniela Vittori

Keyword(s):

Endothelial Cells ◽

Cell Migration ◽

Cross Talk ◽

Protein Tyrosine Phosphatase ◽

Tyrosine Phosphatase ◽

Endothelial Cell Migration ◽

Protein Tyrosine Phosphatase 1B ◽

Vascular Events ◽

Protein Tyrosine ◽

Sensitizing Effect

AbstractThe proliferation and migration of endothelial cells are vascular events of inflammation, a process which can also potentiate the effects of promigratory factors. With the aim of investigating possible modifications in the activity of erythropoietin (Epo) in an inflammatory environment, we found that Epo at a non-promigratory concentration was capable of stimulating EA.hy926 endothelial cell migration when TNF-α was present. VCAM-1 and ICAM-1 expression, as well as adhesion of monocytic THP-1 cells to endothelial layers were also increased. Structurally modified Epo (carbamylation or N-homocysteinylation) did not exhibit these effects. The sensitizing effect of TNF-α on Epo activity was mediated by the Epo receptor. Inhibition assays targeting the PI3K/mTOR/NF-κB pathway, shared by Epo and TNF-α, show a cross-talk between both cytokines. As observed in assays using antioxidants, cell migration elicited by TNF-α + Epo depended on TNF-α-generated reactive oxygen species (ROS). ROS-mediated inactivation of protein tyrosine phosphatase 1B (PTP1B), involved in Epo signaling termination, could explain the synergistic effect of these cytokines. Our results suggest that ROS generated by inflammation inactivate PTP1B, causing the Epo signal to last longer. This mechanism, along with the cross-talk between both cytokines, could explain the sensitizing action of TNF-α on the migratory effect of Epo.

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Protein phosphatase 2A is a specific protamine-kinase-inactivating phosphatase

Biochemical Journal ◽

10.1042/bj2871019 ◽

1992 ◽

Vol 287 (3) ◽

pp. 1019-1022 ◽

Cited By ~ 15

Author(s):

G D Amick ◽

S A G Reddy ◽

Z Damuni

Keyword(s):

Protein Tyrosine Phosphatase ◽

Protein Phosphatase ◽

Kinase Activity ◽

Protein Phosphatase 2A ◽

Tyrosine Phosphatase ◽

Protein Phosphatase 1 ◽

Protein Phosphatase 2B ◽

2B Protein ◽

Phosphatase 2A ◽

Protamine Kinase

Purified preparations of a protamine protein kinase from bovine kidney cytosol [Damuni, Amick & Sneed (1989) J. Biol. Chem. 264, 6412-6416] were inactivated after incubation with near-homogeneous preparations of protein phosphatase 2A1 and protein phosphatase 2A2. These protein phosphatase 2A-mediated inactivations of the protamine kinase were unaffected by highly purified preparations of inhibitor 2, but were prevented when the incubations were performed in the presence of 100 nM microcystin-LR, 100 nM okadaic acid or 0.2 mM-ATP. By contrast, highly purified preparations of protein phosphatase 2B, protein phosphatase 2C, the catalytic subunit of protein phosphatase 1, and two forms of a protein tyrosine phosphatase, designated PTPase 1B and T-cell PTPase, had little effect, if any, on protamine kinase activity. Purified preparations of the protamine kinase did not react with anti-phosphotyrosine antibodies, as determined by Western blotting and immunoprecipitation analysis. The results indicate that protein phosphatase 2A is a specific protamine-kinase-inactivating phosphatase.

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Protein Tyrosine Phosphatase 1B(PTP1B) promotes melanoma cells progression through Src activation

Bioengineered ◽

10.1080/21655979.2021.1988376 ◽

2021 ◽

Author(s):

Qiang Wang ◽

Yuyan Pan ◽

Liping Zhao ◽

Fazhi Qi ◽

Jiaqi Liu

Keyword(s):

Protein Tyrosine Phosphatase ◽

Tyrosine Phosphatase ◽

Melanoma Cells ◽

Protein Tyrosine Phosphatase 1B ◽

Protein Tyrosine ◽

Src Activation

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Cross Talk Between Serine/Threonine Protein Phosphatase 2A and Tyrosine Kinase Src Regulates αIIbβ3 Function

Blood ◽

10.1182/blood.v112.11.2871.2871 ◽

2008 ◽

Vol 112 (11) ◽

pp. 2871-2871

Author(s):

Subhashree Pradhan ◽

Vimal Patel ◽

K. Vinod Vijayan

Keyword(s):

Tyrosine Kinase ◽

Cross Talk ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Tyrosine Phosphatase ◽

Catalytic Subunit ◽

Cellular Functions ◽

Small Interference Rna ◽

293 Cells ◽

Phosphatase 2A

Abstract Protein phosphatase 2A (PP2A) is a ubiquitously expressed serine/threonine phosphatase that regulates a variety of cellular functions. In the context of the platelets, we have previously shown that a pool of the catalytic subunit of PP2A (PP2Ac) associates constitutively with the resting αIIbβ3 and negatively regulates αIIbβ3 signaling. However, the mechanism by which PP2Ac controls αIIbβ3 adhesive function is incompletely understood. In this study, we demonstrated that PP2Ac expressed as a GST fusion protein interacts with the tyrosine kinase Src. Activation of Src is essential to initiate αIIbβ3 outside-in signaling. Small interference RNA mediated knockdown of endogenous PP2Acα expression in 293 cells overexpressing αIIbβ3 (293-αIIbβ3) and murine megakaryocytes, resulted in the activation of Src, as evidenced by the dephosphorylation of Src Tyr-529 and phosphorylation of Src Tyr-418. In contrast to PP2Acα, knockdown of the catalytic subunit of protein phosphatase 1 (PP1cα) did not activate Src, indicating that the regulation of Src activity by PP2Ac is specific. Dephosphorylation of Src Tyr-529 was not observed in PP2Aca depleted 293 cells treated with sulfanamido-benzbromarone compound, a selective protein tyrosine phosphatase 1 (PTP-1) inhibitor. These results suggest that inhibition of PP2Ac may activate a tyrosine phosphatase, capable of dephosphorylating Src Tyr-529. Activation of Src in PP2Ac depleted 293-αIIbβ3 cells had functional consequences for integrin αIIbβ3. PP2Ac depleted 293-αIIbβ3 cells exhibited ~2 fold increased adhesion to immobilized fibrinogen. Inhibition of Src kinase with a pharmacological agent PP2 but not by PP3 an inactive analogue of PP2, abolished the increased adhesiveness of PP2Acα–depleted 293 cells to fibrinogen. Finally, the increased activation of extracellular signal-regulated kinase (ERK1/2) in PP2Acα-depleted cells that we previously demonstrated was also blocked by Src inhibitor PP2 but not by PP3. These results indicate that both Src and ERK1/2 are activated in response to PP2Ac inhibition, with activation of Src being upstream of ERK1/2. These studies illustrate that inhibition of PP2Ac promotes αIIbβ3 adhesiveness by activating Src, and imply that the control of αIIbβ3 adhesive function can be further fine-tuned by a cross talk between the serine/threonine phosphatase PP2A and the tyrosine kinase Src.

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