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Macrophage colony-stimulating factor induces the expression of mitogen-activated protein kinase phosphatase-1 through
A F Valledor1, J Xaus, L Marquès
1Departament de Fisiologia (Biologia del Macròfag), Facultat de Biologia and Fundació August Pi i Sunyer, Universitat de Barcelona, Spain.
Abstract:
M-CSF triggers the activation of extracellular signal-regulated protein kinases (ERK)-1/2. We show that inhibition of this pathway leads to the arrest of bone marrow macrophages at the G0/G1 phase of the cell cycle without inducing apoptosis. M-CSF induces the transient expression of mitogen-activated protein kinase phosphatase-1 (MKP-1), which correlates with the inactivation of ERK-1/2. Because the time course of ERK activation must be finely controlled to induce cell proliferation, we studied the mechanisms involved in the induction of MKP-1 by M-CSF. Activation of ERK-1/2 is not required for this event. Therefore, M-CSF activates ERK-1/2 and induces MKP-1 expression through different pathways. The use of two protein kinase C (PKC) inhibitors (GF109203X and calphostin C) revealed that M-CSF induces MKP-1 expression through a PKC-dependent pathway. We analyzed the expression of different PKC isoforms in bone marrow macrophages, and we only detected PKCbetaI, PKCepsilon, and PKCzeta. PKCzeta is not inhibited by GF109203X/calphostin C. Of the other two isoforms, PKCepsilon is the best candidate to mediate MKP-1 induction. Prolonged exposure to PMA slightly inhibits MKP-1 expression in response to M-CSF. In bone marrow macrophages, this treatment leads to a complete depletion of PKCbetaI, but only a partial down-regulation of PKCepsilon. Moreover, no translocation of PKCbetaI or PKCzeta from the cytosol to particulate fractions was detected in response to M-CSF, whereas PKCepsilon was constitutively present at the membrane and underwent significant activation in M-CSF-stimulated macrophages. In conclusion, we remark the role of PKC, probably isoform epsilon, in the negative control of ERK-1/2 through the induction of their specific phosphatase.
Insights
Macrophage colony-stimulating factor (M-CSF) activates extracellular signal-regulated kinases (ERK)-1/2 and induces mitogen-activated protein kinase phosphatase-1 (MKP-1) via distinct pathways. Protein kinase C (PKC) epsilon mediates M-CSF-induced MKP-1 expression, negatively regulating ERK-1/2.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- Macrophage colony-stimulating factor (M-CSF) is crucial for macrophage proliferation and survival.
- Extracellular signal-regulated kinases (ERK)-1/2 are key regulators of cell cycle progression.
- Mitogen-activated protein kinase phosphatase-1 (MKP-1) deactivates ERK-1/2, controlling their activity duration.
Purpose of the Study:
- To elucidate the signaling pathways by which M-CSF regulates ERK-1/2 activation and MKP-1 expression.
- To identify the specific protein kinase C (PKC) isoforms involved in M-CSF-induced MKP-1 expression.
- To understand the role of PKC in the negative feedback control of ERK-1/2 by MKP-1.
Main Methods:
- Bone marrow macrophages were treated with M-CSF.
- ERK-1/2 and MKP-1 expression and activation were assessed.
- PKC inhibitors (GF109203X, calphostin C) were used to study PKC involvement.
- PKC isoform expression, localization, and activation were analyzed.
Main Results:
- M-CSF induced G0/G1 cell cycle arrest via ERK-1/2 inhibition, without apoptosis.
- M-CSF triggered transient MKP-1 expression, correlating with ERK-1/2 inactivation.
- M-CSF activated ERK-1/2 and induced MKP-1 through separate signaling cascades.
- PKC activation, specifically PKCepsilon, was essential for M-CSF-induced MKP-1 expression.
- PKCepsilon translocation and activation were observed in M-CSF-stimulated macrophages.
Conclusions:
- M-CSF employs distinct pathways to activate ERK-1/2 and induce MKP-1.
- PKCepsilon plays a critical role in mediating M-CSF-induced MKP-1 expression.
- PKCepsilon-induced MKP-1 negatively regulates ERK-1/2 activity, controlling macrophage proliferation.