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Regulation and Function of MAP Kinases in PDGF Signaling
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Ludwig Institute for Cancer Research.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Platelet-derived growth factor (PDGF) is a family of signaling molecules that stimulates cell growth, survival and migration. PDGF is recognized by specific transmembrane proteins, the PDGF receptors, which relay the signals to the cell activating the Mitogen-activated protein (MAP) kinases and other signaling pathways. Aberrant activation of these pathways is frequently detected in cancer. Hence, the study of these processes is essential for identifying potential drug targets or diagnostic markers.

In paper I, we identified Receptor Subfamily 4 Group A Member 1 NR4A1 to be regulated by PDGF via MAP kinases, clarifying the role of Extracellular signal–regulated kinases (Erk) 1/2, Erk5 and Nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) in its regulation. NR4A1 was found to be important for the tumorigenic potential, measured as anchorage-independent growth, of glioblastoma cells.

Since the cellular responses elicited by PDGF result from the balance between phosphorylation and dephosphorylation events, we investigated the role of the dual specificity phosphatases DUSP4/MKP-2 and DUSP6/MKP-3. In paper II, we describe the crucial role of Erk1/2 and p53 in the expression of DUSP4/MKP2. Moreover, we observed that DUSP4/MKP-2 downregulation decreases Erk5 activation and accelerates PDGFRβ internalization and downregulation resulting in a specific inhibition of Signal transducers and activators of transcription (Stat) 3, Src and protein kinase C (PKC), and partially of p38, Stat1/5 and Phoshoplipase Cγ (PLCγ).

In paper III, we report that DUSP6/MKP-3 creates a negative cross-talk between Erk1/2 and Erk5 and an auto-inhibitory feedback loop on the PI3-kinase/Akt pathway. In paper IV, we identify a new regulative mechanism of the PDGF pathway. PDGF induces Erk5 expression and activation that modulates the PDGFRβ activity. After Erk5 downregulation, the receptor undergoes to a faster and stronger activation that results in a faster internalization and degradation.

In conclusion, we present a mechanism through which the PDGF/MAP kinases support tumor growth, and elucidate different regulatory pathways involved in PDGF signaling.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 51 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1246
Keyword [en]
PDGF, PDGFR, MAP kinase, Erk1/2, Erk5, Dusp/MKP, NR4A1, cancer
National Category
Basic Medicine
Research subject
Biology with specialization in Molecular Cell Biology; Medical Cell Biology
Identifiers
URN: urn:nbn:se:uu:diva-301057ISBN: 978-91-554-9660-9OAI: oai:DiVA.org:uu-301057DiVA: diva2:953232
Public defence
2016-10-04, B/B42, BMC, Husargatan 3, Uppsala, 15:00 (English)
Opponent
Supervisors
Available from: 2016-09-13 Created: 2016-08-17 Last updated: 2016-09-22
List of papers
1. NR4A1 Promotes PDGF-BB-Induced Cell Colony Formation in Soft Agar
Open this publication in new window or tab >>NR4A1 Promotes PDGF-BB-Induced Cell Colony Formation in Soft Agar
2014 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 9, no 9, e109047- p.Article in journal (Refereed) Published
Abstract [en]

The fibroblast mitogen platelet-derived growth factor -BB (PDGF-BB) induces a transient expression of the orphan nuclear receptor NR4A1 (also named Nur77, TR3 or NGFIB). The aim of the present study was to investigate the pathways through which NR4A1 is induced by PDGF-BB and its functional role. We demonstrate that in PDGF-BB stimulated NIH3T3 cells, the MEK1/2 inhibitor CI-1040 strongly represses NR4A1 expression, whereas Erk5 downregulation delays the expression, but does not block it. Moreover, we report that treatment with the NF-κB inhibitor BAY11-7082 suppresses NR4A1 mRNA and protein expression. The majority of NR4A1 in NIH3T3 was found to be localized in the cytoplasm and only a fraction was translocated to the nucleus after continued PDGF-BB treatment. Silencing NR4A1 slightly increased the proliferation rate of NIH3T3 cells; however, it did not affect the chemotactic or survival abilities conferred by PDGF-BB. Moreover, overexpression of NR4A1 promoted anchorage-independent growth of NIH3T3 cells and the glioblastoma cell lines U-105MG and U-251MG. Thus, whereas NR4A1, induced by PDGF-BB, suppresses cell growth on a solid surface, it increases anchorage-independent growth.

National Category
Cancer and Oncology
Identifiers
urn:nbn:se:uu:diva-233387 (URN)10.1371/journal.pone.0109047 (DOI)000343671700217 ()25269081 (PubMedID)
Funder
Swedish Research Council, K2011-67X-21859-01-6Swedish Cancer Society, 130519
Available from: 2014-10-02 Created: 2014-10-02 Last updated: 2016-08-25Bibliographically approved
2. Depletion of DUSP4 results in enhanced PDGFRβ cell surface clearance and suppression of PDGF-BB-induced activation of Erk5, Stat3, Src and PKC
Open this publication in new window or tab >>Depletion of DUSP4 results in enhanced PDGFRβ cell surface clearance and suppression of PDGF-BB-induced activation of Erk5, Stat3, Src and PKC
(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-301761 (URN)
Available from: 2016-08-24 Created: 2016-08-24 Last updated: 2016-08-25
3. MKP3 negatively modulates PDGF-induced Akt and Erk5 phosphorylation as well as chemotaxis
Open this publication in new window or tab >>MKP3 negatively modulates PDGF-induced Akt and Erk5 phosphorylation as well as chemotaxis
Show others...
2012 (English)In: Cellular Signalling, ISSN 0898-6568, E-ISSN 1873-3913, Vol. 24, no 3, 635-640 p.Article in journal (Refereed) Published
Abstract [en]

MAP kinase phosphatase-3 (MKP3), also known as DUSP6 or Pyst1, is a dual specificity phosphatase considered to selectively dephosphorylate extracellular-signal-regulated kinase 1/2 (Erk1/2). Here, we report that in NIH3T3 cells, MKP3 is induced in response to platelet-derived growth factor (PDGF)-BB treatment in an Erk1/2- and phosphatidylinositol 3-kinase (PI3K)-dependent manner, but independently of Erk5 expression. Silencing of MKP3 expression did not affect PDGF-BB-induced Erk1/2 or p38 phosphorylation; however, their basal level of phosphorylation was elevated. Furthermore, we found that PDGF-BB-mediated activation of Erk5 and Akt was enhanced when the MKP3 expression was reduced. Interfering with Mek1/2 or PI3K using the inhibitors CI-1040 and LY-294002, respectively, inhibited PDGF-BB-induced MKP3 expression. Functionally, we found that MKP3 silencing did not affect cell proliferation, but enhanced the chemotactic response toward PDGF-BB. Although both Akt and Erk5 have been linked to increased cell survival, downregulation of MKP3 did not alter the ability of PDGF-BB to protect NIH3T3 cells from starvation-induced apoptosis. However, we observed an increased apoptosis in untreated cells with reduced MKP3 expression. In summary, our data indicate that there is negative cross-talk between Erk1/2 and Erk5 that involves regulation of MKP3 expression, and that PI3K in addition to promoting Akt phosphorylation also negatively modulates Akt, through MKP3 expression.

Keyword
Non-Smads, Smads, TAK1, TGF beta, TRAF6
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-168808 (URN)10.1016/j.cellsig.2011.11.001 (DOI)000300478400007 ()22100392 (PubMedID)
Available from: 2012-02-15 Created: 2012-02-15 Last updated: 2016-08-25Bibliographically approved
4. Erk5 promotes prolonged PDGFRβ activation by limiting ligand-induced receptor internalization and degradation
Open this publication in new window or tab >>Erk5 promotes prolonged PDGFRβ activation by limiting ligand-induced receptor internalization and degradation
(English)Manuscript (preprint) (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-301762 (URN)
Available from: 2016-08-24 Created: 2016-08-24 Last updated: 2016-08-25

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