Haematopoietic Colony Stimulating Factors CSF-1 and GM-CSF Increase Phosphatidylinositol 3-Kinase Activity in Murine Bone Marrow-Derived Macrophages

221

153

Vascular endothelial growth factor (VEGF) receptorFlk-1/KDR in endothelial cells is activated during vasculogenesis and angiogenesis upon ligand-receptor interaction. Activated Flk-1/KDR has been shown to recruit Src homology 2 domain-containing signaling molecules that are known to serve as links to the activation of the mitogen-activated protein (MAP) kinase signaling pathway. To define the functional significance of phosphatidylinositol (PI) 3-kinase in VEGF signaling, we have examined its role in human umbilical vein endothelial cell (HUVEC) cycle progression. We show herein that p85, the regulatory subunit of PI 3-kinase, is constitutively associated with Flk-1/KDR. The treatment of HUVECs with VEGF promoted tyrosine autophosphorylation of Flk-1/KDR and also induced phosphorylation of p85. This was followed by an increase in the PI 3-kinase activity, which was sensitive to wortmannin, a potent PI 3-kinase inhibitor. VEGF also induced a striking activation of MAP kinase in a time-dependent manner. Inhibition studies with both a dominant-negative p85 mutant and the PI 3-kinase inhibitor, wortmannin, were employed to show for the first time that VEGF-stimulated PI 3-kinase modulates MAP kinase activation and nuclear events such as transcription from c-fos promoter and entry into the synthesis (S)-phase. Our data demonstrate the importance of PI 3-kinase as a necessary signaling component of VEGF-mediated cell cycle progression.

Section: Discussionsupporting

confidence: 81%

The Role of Phosphatidylinositol 3-Kinase in Vascular Endothelial Growth Factor Signaling

Thakker¹,

Hajjar

Müller

et al. 1999

221

153

“…For example, Iwama et al have shown that association of PI 3-kinase with the platelet-derived growth factor receptor of vascular smooth muscle cells appears to be necessary for platelet-derived growth factor-induced cellular mitogenesis (45). Yusoff et al concluded that PI 3-kinase activation may be involved in growth stimulation of bone marrow-derived macrophage by hematopoietic growth factors CSF-1 and GM-CSF (46). In these studies, CSF-1 and GM-CSF stimulated a dosedependent activation of PI 3-kinase, whereas concanavalin A, PMA, and formyl-methionyl-leucyl-phenylalanine had no mitogenic activity and did not significantly increase PI 3-kinase activity.…”

Section: Discussionmentioning

confidence: 81%

Phosphatidylinositol 3-Kinase Is Involved in the Induction of Macrophage Growth by Oxidized Low Density Lipoprotein

Martens¹,

Reiner²,

Herrera-Velit³

et al. 1998

Early atherosclerotic lesions are characterized by the presence of cholesterol-rich, macrophage-derived foam cells. It has recently been shown that macrophage proliferation occurs during the development of early lesions and that oxidized low density lipoprotein (LDL) stimulates macrophage growth. Possible mechanisms for this induction of macrophage growth include potentiation of mitogenic signal transduction by a component of oxidized LDL following internalization and degradation, interaction with integral plasma membrane proteins coupled to signaling pathways, or direct or indirect activation of growth factor receptors on the cell surface (e.g. GM-CSF receptor) through an autocrine/ paracrine mechanism. The present study was undertaken to characterize some of the early intracellular signaling events by which oxidized LDL mediates macrophage cell growth. Extensively oxidized LDL increased protein-tyrosine phosphorylation and caused a 2-fold increase in phosphatidylinositol (PI) 3-kinase activity in phorbol ester-pretreated THP-1 cells (a human monocyte-like cell line). Similar concentrations of native LDL had no effect. Oxidized LDL also stimulated growth of resident mouse peritoneal macrophages, and this effect was reduced by 40 -50% in cells treated with PI 3-kinase inhibitors (100 nM wortmannin or 20 M LY294002). These results suggest that PI 3-kinase mediates part of the mitogenic effect of oxidized LDL, but parallel pathways involving other receptors and signal transduction pathways are likely also involved.

“…2 illustrate that, at the short times tested, fMet-Leu-Phe did not modify the PI3K activity of p85/p110. In control experiments, granulocyte/macrophage colony-stimulating factor (1 nM, 10 min), as previously shown (3,8,34,41), stimulated the activity of p85/p110 by more than 80% (data not shown).…”

Section: Resultsmentioning

confidence: 99%

Stimulation of Human Neutrophils by Chemotactic Factors Is Associated with the Activation of Phosphatidylinositol 3-Kinase γ

Naccache¹,

Levasseur²,

Lachance³

et al. 2000

The activation of human polymorphonuclear neutrophil leukocytes (neutrophils) is associated with an increased synthesis of the highly phosphorylated phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P 3 ). The aims of the present investigation were to determine whether the newly described, G protein-dependent phosphatidylinositol 3-kinase (PI3K), p110␥, was involved in the responses to chemotactic factors interacting with G protein-coupled receptors. The presence of p110␥ in neutrophils was first established both at the protein and the mRNA level. Stimulation of the cells with fMet-Leu-Phe or interleukin-8 increased the PI3K activity in p110␥, but not p85, immunoprecipitates. The time course of this effect (threshold within less than 5 s, maximal activation at 10 -15 s) was consistent with that of the generation of PtdIns(3,4,5)P 3 . Wortmannin, a PI3K inhibitor, abrogated the effects of fMet-Leu-Phe, which were also significantly inhibited by pertussis toxin. Finally, fMet-Leu-Phe also induced a significant translocation of p110␥ to a particulate fraction derived from these cells. These data indicate that p110␥ represent the major PI3K activated by fMet-Leu-Phe and interleukin-8 at very early time points following the stimulation of human neutrophils.