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Tsioumpekou, Maria
Publications (5 of 5) Show all publications
Tsioumpekou, M. (2019). Studies of PDGF receptor signaling in vitro and in vivo. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Studies of PDGF receptor signaling in vitro and in vivo
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Platelet-derived growth factor receptor (PDGFR) signaling is essential for proliferation, migration and survival of cells of mesenchymal origin; however, its deregulation has been associated with various diseases, including cancer. The aim of this thesis was to clarify the molecular mechanisms of PDGFR signaling regulation. We have studied PDGFR downregulation, identified the E3 ligases and deubiquitinases (DUBs) acting on the receptor, characterized the role of the downstream effector Erk5, as well as elucidated the role of PDGFRβ isoform in tumor growth and angiogenesis.

As Erk5 activation has been associated with tumorigenesis, it is important to delineate the pathway from activated PDGFR to Erk5. Here, we demonstrate not only a complex mechanism for PDGF-induced Erk5 activation that involves Mek5, Mekk2, Mek1/2, PI3K and classical PKCs, but also a novel function for Erk5 by showing that PDGF-BB affects BMP-Smad signaling in an Erk5 pathway-dependent manner, indicating a crosstalk between tyrosine kinase receptor and serine/threonine receptor signaling.

By investigating PDGFRβ downregulation, we demonstrated that ubiquitination of PDGFRβ, mediated by Cbl-b and c-Cbl, is essential for the receptor internalization, signaling, as well as downstream biological responses. Additionally, as ubiquitination is a reversible post-translational modification, we identified USP4 as one of the DUBs acting on PDGFRβ and discovered that USP4 interacts with PDGFRβ, removing both K48- and K63-linked polyubiquitin chains, and increases its stability, in both normal and cancer cells.

Although several studies have highlighted the therapeutic benefit of PDGFR inhibition in cancer treatment, all available PDGFR kinase inhibitors have secondary targets; consequently, the details underlying the importance of PDGFR in tumorigenesis remain unknown. By targeting specifically PDGFRβ in the stroma of various tumor models, we showed that specific inhibition of PDGFRβ signaling suppresses growth of tumors with high levels of PDGF-BB, whereas the multi-target kinase inhibitor imatinib has less effect, indicating the significance of selective targeting of PDGFRβ.

Our data provide new insights into the molecular events underlying PDGFRβ signaling and downregulation, highlight its importance as cancer therapeutic target and lead the way for further discoveries.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 67
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1538
Keywords
PDGF, signaling, cancer, Erk5, kinase, Cbl, ubiquitination, deubiquitinase, pericytes, tumor growth, angiogenesis, low molecular weight inhibitors
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-376248 (URN)978-91-513-0571-4 (ISBN)
Public defence
2019-03-22, B42, Biomedical Center, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2019-02-27 Created: 2019-02-03 Last updated: 2019-03-18
Reyhani, V., Tsioumpekou, M., van Wieringen, T., Rask, L., Lennartsson, J. & Rubin, K. (2017). PDGF-BB enhances collagen gel contraction through a PI3K-PLCγ-PKC-cofilin pathway. Scientific Reports, 7(1), Article ID 8924.
Open this publication in new window or tab >>PDGF-BB enhances collagen gel contraction through a PI3K-PLCγ-PKC-cofilin pathway
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 8924Article in journal (Refereed) Published
Abstract [en]

Cell-mediated contraction of collagenous matrices is modulated by various growth factors and cytokines, such as platelet-derived growth factor-BB (PDGF-BB). Here we used a genetic cell model to delineate defined signaling pathways that enhance collagen gel contraction downstream of ligand-stimulated platelet-derived growth factor receptor-β (PDGF-Rβ). Our data show that PDGF BB-enhanced activations of phosphatidylinositol 3'-kinase (PI3K) and phospholipase Cγ (PLCγ) were necessary for PDGF-enhanced collagen gel contraction. Importantly, other defined signaling pathways down-stream of PDGF-Rβ were, however, dispensable. The decisive roles for PI3K and PLCγ were corroborated by experiments using selective inhibitors. Furthermore, we show that de-phosphorylation and thereby activation of cofilin that is important for the turnover of actin filaments, is depended on PI3K and PLCγ down-stream of PDGF-Rβ. Moreover, inhibition of protein kinase C (PKC) by GÖ6976 and bisindolylmaleimide-II abolished cofilin de-phosphorylation, as well as PDGF-enhanced contraction. In contrast, activation of the PKC protein family by 4β-phorbol 12-myristate 13-acetate (PMA) did not accelerate collagen gel contraction although it induced long-term cofilin de-phosphorylation, showing the need of a dynamic control of cofilin de-phosphorylation for PDGF-enhanced collagen gel contraction. Taken together, our data point to the involvement of a PI3K/PLCγ-PKC-cofilin pathway in both PDGF-enhanced cofilin de-phosphorylation and PDGF-enhanced collagen gel contraction.

National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:uu:diva-331647 (URN)10.1038/s41598-017-08411-1 (DOI)000408107000058 ()28827622 (PubMedID)
Funder
Swedish Cancer SocietySwedish Research Council
Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2018-09-07Bibliographically approved
Delis, C., Krokida, A., Tomatsidou, A., Tsikou, D., Beta, R. A. A., Tsioumpekou, M., . . . Papadopoulou, K. K. (2016). AtHESPERIN: a novel regulator of circadian rhythms with poly(A)-degrading activity in plants. RNA Biology, 13(1), 68-82
Open this publication in new window or tab >>AtHESPERIN: a novel regulator of circadian rhythms with poly(A)-degrading activity in plants
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2016 (English)In: RNA Biology, ISSN 1547-6286, E-ISSN 1555-8584, Vol. 13, no 1, p. 68-82Article in journal (Refereed) Published
Abstract [en]

We report the identification and characterization of a novel gene, AtHesperin (AtHESP) that codes for a deadenylase in Arabidopsis thaliana. The gene is under circadian clock-gene regulation and has similarity to the mammalian Nocturnin. AtHESP can efficiently degrade poly(A) substrates exhibiting allosteric kinetics. Size exclusion chromatography and native electrophoresis coupled with kinetic analysis support that the native enzyme is oligomeric with at least 3 binding sites. Knockdown and overexpression of AtHESP in plant lines affects the expression and rhythmicity of the clock core oscillator genes TOC1 and CCA1. This study demonstrates an evolutionary conserved poly(A)-degrading activity in plants and suggests deadenylation as a mechanism involved in the regulation of the circadian clock. A role of AtHESP in stress response in plants is also depicted.

Keywords
nocturnin, Arabidopsis, Allosteric, circadian, RNA stability, deadenylation
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-282644 (URN)10.1080/15476286.2015.1119363 (DOI)000370963300008 ()26619288 (PubMedID)
Available from: 2016-04-06 Created: 2016-04-06 Last updated: 2017-11-30Bibliographically approved
Rorsman, C., Tsioumpekou, M., Heldin, C.-H. & Lennartsson, J. (2016). The Ubiquitin Ligases c-Cbl and Cbl-b Negatively Regulate Platelet-derived Growth Factor (PDGF) BB-induced Chemotaxis by Affecting PDGF Receptor beta (PDGFR beta) Internalization and Signaling. Journal of Biological Chemistry, 291(22), 11608-11618
Open this publication in new window or tab >>The Ubiquitin Ligases c-Cbl and Cbl-b Negatively Regulate Platelet-derived Growth Factor (PDGF) BB-induced Chemotaxis by Affecting PDGF Receptor beta (PDGFR beta) Internalization and Signaling
2016 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, no 22, p. 11608-11618Article in journal (Refereed) Published
Abstract [en]

Protein ubiquitination controls protein stability and subcellular localization of tyrosine kinase receptors, hence affecting signaling both quantitatively and qualitatively. In this report, we demonstrate that, after ligand stimulation, the PDGF beta receptor (PDGFR beta) becomes ubiquitinated in a manner requiring both the c-Cbl and Cbl-b ubiquitin ligases. Simultaneous depletion of c-Cbl and Cbl-b resulted in reduced ligand-induced PDGFR beta clearance from the cell surface because of reduced endocytosis of the receptor. Cbl-b formed a complex with c-Cbl, as well as with the PDGFR beta, in response to PDGF-BB stimulation. We were unable to find a direct interaction between the receptor and c-Cbl, raising the possibility that Cbl-b is necessary for c-Cbl to interact with PDGFR beta. Phosphorylated Tyr-1021 in PDGFR beta was the primary interaction site for Cbl-b, with some contribution from Tyr-1009. Depletion of c-Cbl and Cbl-b led to an increased ligand-induced tyrosine phosphorylation of the receptor. Several tyrosine residues with elevated phosphorylation (i.e. Tyr-579, Tyr-581, Tyr-1009, and Tyr-1021) have previously been shown to interact with Src kinases and PLC gamma. Indeed, in cells depleted of c-Cbl and Cbl-b, both Src and PLC gamma phosphorylation were enhanced, whereas activation of other pathways, such as Erk1/2 MAP kinase and Akt, were not affected. In addition, Stat3 phosphorylation, which has been connected to Src activity, was also elevated in cells lacking c-Cbl and Cbl-b. Functionally, we found that cells depleted of c-Cbl and Cbl-b were more prone to migrate toward PDGF-BB, whereas no reproducible effect on cell proliferation could be observed. In conclusion, internalization as well as signaling via PDGFR beta are controlled by ubiquitination.

National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:uu:diva-299504 (URN)10.1074/jbc.M115.705814 (DOI)000377264800013 ()27048651 (PubMedID)
Funder
Swedish Cancer Society
Available from: 2016-07-22 Created: 2016-07-22 Last updated: 2019-02-03Bibliographically approved
Tsioumpekou, M., Papadopoulos, N., Burovic, F., Heldin, C.-H. & Lennartsson, J. (2015). Mechanism of platelet-derived growth factor (PDGF) Erk5 MAP-kinase activation is cell type-dependent and can be independent of PDGF receptor kinase activity. Paper presented at 20th World Congress on Advances in Oncology and 18th International Symposium on Molecular Medicine October 8-10, 2015. International Journal of Molecular Medicine, 36(Supplement: 1), S20-S20
Open this publication in new window or tab >>Mechanism of platelet-derived growth factor (PDGF) Erk5 MAP-kinase activation is cell type-dependent and can be independent of PDGF receptor kinase activity
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2015 (English)In: International Journal of Molecular Medicine, ISSN 1107-3756, E-ISSN 1791-244X, Vol. 36, no Supplement: 1, p. S20-S20Article in journal, Meeting abstract (Other academic) Published
National Category
Dentistry
Identifiers
urn:nbn:se:uu:diva-266290 (URN)000361863000064 ()
Conference
20th World Congress on Advances in Oncology and 18th International Symposium on Molecular Medicine October 8-10, 2015
Available from: 2015-11-06 Created: 2015-11-06 Last updated: 2017-12-01Bibliographically approved
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