Actin reorganization and morphological changes in human neutrophils stimulated by TNF, GM-CSF, and G-CSF: the role of MAP kinases

Abstract

Stimulation of human neutrophils with tumor necrosis factor-α (TNF), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte CSF (G-CSF) resulted in decreased fluorescence intensity of FITC-phalloidin (actin depolymerization) and morphological changes. Cytokine-induced actin depolymerization was dependent on the concentration of cytokines used as stimuli. The maximal changes were detected at 10 min after stimulation with TNF or GM-CSF and at 20 min after stimulation with G-CSF. Cytokine-induced actin depolymerization was sustained for at least 30 min after stimulation. In contrast, N-formyl-methionyl-leucyl-phenylalanine (FMLP) rapidly (within 45 s) induced an increase in the fluorescence intensity of FITC-phalloidin (actin polymerization) and morphological changes. TNF- and GM-CSF-induced actin depolymerization and morphological changes, but not FMLP-induced responses, were partially inhibited by either PD-98059, an inhibitor of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase, or SB-203580, an inhibitor of p38 MAPK, and were almost completely abolished by these inhibitors in combination. G-CSF-induced responses were almost completely abolished by PD-98059 and were unaffected by SB-203580. These findings are consistent with the ability of these cytokines to activate the distinct MAPK subtype cascade in human neutrophils. Phosphorylated ERK and p38 MAPK were not colocalized with F-actin in neutrophils stimulated by cytokines or FMLP. Furthermore, FMLP-induced polarization and actin polymerization were prevented by cytokine pretreatment. These findings suggest that TNF, GM-CSF, and G-CSF induce actin depolymerization and morphological changes through activation of ERK and/or p38 MAPK and that cytokine-induced actin reorganization may be partly responsible for the inhibitory effect of these cytokines on neutrophil chemotaxis.

Identification of target actin content and polymerization status as a mechanism of tumor resistance after cytolytic T lymphocyte pressure

“…Our present results provide further evidence for the concept of immune selection in neoplastic development by showing that CTL selection pressure can lead to a striking adaptation of the tumor target, involving morphological change to escape immune surveillance. Although the mechanisms by which CTL selection pressure contributes to morphological changes remain to be fully elucidated, it has been recently reported that cytokines, including TNF, can induce actin depolymerization and morphological changes through activation of ERK and orp38 mitogen-activated protein kinase (28).…”

WAVE2 regulates meiotic spindle stability, peripheral positioning and polar body emission in mouse oocytes

“…7 Since meiotic spindles in oocytes lack centrosomes, MTOCs (microtubule organization centers) act as centrosomes, indicating that a specialized mechanism may be responsible for the off-centre positioning of the spindles. Cdc42, aPKC, Formin, Fyn, Myosin, MLCK and the MAPK pathway are involved in spindle positioning in mouse oocytes.…”

Neutrophil Signaling Pathways Activated by Bacterial DNA Stimulation

“…In fact, activation of overlapping but distinct MAPK subtype cascades has been demonstrated in human neutrophils stimulated with different agonists (15)(16)(17)(18)(19). Therefore, to delineate the signaling intermediates activated by bacterial DNA, neutrophils were stimulated with E. coli DNA (100 g/ml) for different times at 37°C.…”