Protein tyrosine kinase activity is essential for Fc gamma receptor-mediated intracellular killing of Staphylococcus aureus by human monocytes

Abstract

Our previous study revealed that the intracellular killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma receptor I (Fc gamma RI) or Fc gamma RII is a phospholipase C (PLC)-dependent process. The aim of the present study was to investigate whether protein tyrosine kinase (PTK) activity plays a role in the Fc gamma R-mediated intracellular killing of bacteria and activation of PLC in these cells. The results showed that phagocytosis of bacteria by monocytes was not affected by the PTK inhibitors genistein and tyrphostin-47. The intracellular killing of S. aureus by monocytes after cross-linking Fc gamma RII or Fc gamma RII with anti-Fc gamma R monoclonal antibody and a bridging antibody or with human immunoglobulin G (IgG) was inhibited by these compounds in a dose-dependent fashion. The production of O2- by monocytes after stimulation with IgG or IgG-opsonized S. aureus was almost completely blocked by the PTK inhibitor. These results indicate that inhibition of PTK impairs the oxygen-dependent bactericidal mechanisms of monocytes. Genistein and tyrphostin-47, which do not affect the enzymatic activity of purified PLC, prevented activation of PLC after cross-linking Fc gamma RI or Fc gamma RII, measured as an increase in the intracellular inositol 1,4,5-trisphosphate concentration. Cross-linking Fc gamma RI or Fc gamma RII induced rapid tyrosine phosphorylation of several proteins in monocytes, one of which was identified as PLC-gamma 1, and the phosphorylation could be completely blocked by PTK inhibitors, leading to the conclusion that activation of PLC after cross-linking Fc gamma R in monocytes is regulated by PTK activity. Together, these results demonstrate that PTK activity is essential for the activation of PLC which is involved in the Fc gamma R-mediated intracellular killing of S. aureus by human monocytes.

Trp-Lys-Tyr-Met-Val-D-Met stimulates superoxide generation and killing of Staphylococcus aureus via phospholipase D activation in human monocytes

“…These results imply that PKC plays a critical role in the peptide-induced PLD activation, superoxide generation, and the stimulation of bacteriakilling activity in human monocytes. Zheng et al reported that cross-linking of the Fc␥ receptor caused a transient increase in PKC activity in the membrane of monocytes and that pretreatment with PKC inhibitor attenuated the Fc␥ receptor-mediated killing of bacteria by monocytes [45]. Recently, RANTES, one of the C-C family chemokines, was found to activate PLD in Jurkat T cells and that the effect was PKC dependent [46].…”

Rottlerin, a PKC isozyme-selective inhibitor, affects signaling events and cytokine production in human monocytes

“…Differences in their structure, cofactor requirement, substrate specificity, tissue distribution, and subcellular localization suggest that in a given cell type PKC may function in an isozyme-specific manner [21,22]. Cells of monocyte/ macrophage lineage express not only the classical (Ca 2ϩdependent) isoenzymes ␣, ␤I, and ␤II, but also the novel (Ca 2ϩ -independent) isoenzymes ␦ and ⑀, and the atypical isoenzyme [12,[23][24][25]. Data describing the contribution of the respective PKC isoenzymes to the regulation of cell functions are scarce.…”

“…Data describing the contribution of the respective PKC isoenzymes to the regulation of cell functions are scarce. Regarding human monocytes and monocytic cell lines, it has been shown that: (1) different PKC are responsible for the stimulation (PKC␤) and inhibition (PKC␣ and ⑀) of the Fc␥-receptor-mediated intracellular killing of bacteria [25], (2) PKC␣ is required for superoxide anion production [26], (3) PKC ␤ and ␦ are essential for the differentiation into macrophages [27][28][29], whereas (4) PKC␦ and ⑀ are implicated in the signaling pathways leading to apoptosis [30]. The role of individual PKC isoenzymes in the induction of pro-inflammatory cytokine synthesis only recently got some attention.…”

Characterization of bovine neutrophil β2‐adrenergic receptor function

“…This last study also describes direct phosphorylation of the human b 2 -adrenergic receptor by bovine PKC-a, in addition to decreased cAMP production following exposure to 1 · 10 )8 M PMA, suggesting that PMA causes heterologous desensitization of the b 2 -adrenergic receptor via PKC-a activation. Also, PKC-b and PKC-but not PKC-a are reported to translocate to the plasma membrane of human monocytes following cross-linking and activation of either FccRI or FccRII, with PMA stimulating the translocation of all three isozymes (Zheng et al, 1995). Yet, another report describes the translocation of PKC-a, bI, bII, d, , and l isoforms to the RAW 264.7 macrophage plasma membrane following PMA administration (Lin & Chen, 1998).…”