Low affinity Fc gamma receptors on murine macrophages: mitogen-activated protein kinase activation and AP-1 DNA binding activity.

Mouse macrophage cell lines such as J774 express Fc receptors for IgG2a immune complexes, which upon binding of the proper ligand, trigger several signal transduction pathways. A surface to nucleus signaling through these receptors has been demonstrated. We describe here the activation of the mitogen-activated protein kinase (MAPK) and an increase in the binding of the activator protein 1 (AP-1) to DNA upon receptor stimulation. The described effects are only partially blocked by inhibitors of the Ca2+/diacylglycerol-dependent protein kinase (PKC), suggesting that differential signaling pathways are activated upon receptor cross-linking and that they converge at or above the MAPK level. These results pave the way to our understanding of Fc gammaR cross-linking induced gene expression regulation.