ACTIVATION OF THE MITOGEN-ACTIVATED PROTEIN-KINASE CYTOSOLIC PHOSPHOLIPASE A(2) PATHWAY IN A RAT MAST-CELL LINE - INDICATIONS OF DIFFERENT PATHWAYS FOR RELEASE OF ARACHIDONIC-ACID AND SECRETORY GRANULES
N. Hirasawa et al., ACTIVATION OF THE MITOGEN-ACTIVATED PROTEIN-KINASE CYTOSOLIC PHOSPHOLIPASE A(2) PATHWAY IN A RAT MAST-CELL LINE - INDICATIONS OF DIFFERENT PATHWAYS FOR RELEASE OF ARACHIDONIC-ACID AND SECRETORY GRANULES, The Journal of immunology, 154(10), 1995, pp. 5391-5402
The role of mitogen-activated protein (MAP) kinase in the release of a
rachidonic acid was examined in a mutated mast cell (RBL-2H3(ml)) line
that expressed both native Fc epsilon R1 and the G protein-coupled mu
scarinic mi receptor. Stimulation of these cells with Ag, carbachol, C
a2+-ionophore, or thapsigargin resulted in the phosphorylation of Raf1
, MEK1, p42(mapk) MAp kinase, and the recently cloned cytosolic phosph
olipase A(2) (PLA(2)) and increased activities of both MAP kinase and
PLA(2), as well as release of arachidonic acid. Because this cascade o
f reactions was inhibited by guanosine 5'-(2-thiodiphosphate), it appe
ared to be dependent on a GTP-binding protein(s). These reactions, how
ever, were not dependent on protein kinase C; the cascade was totally
resistant to the actions of a selective protein kinase C inhibitor, Ro
31-7549, whereas release of the secretory granule marker, hexosaminida
se, was blocked by this agent. Differences between the stimulatory pat
hways for release of arachidonic acid and hexosaminidase were evident
also from the effects of the kinase inhibitor, quercetin. The above ca
scade of reactions, including release of arachidonic acid, was inhibit
ed by 50% with similar to 5 ELM quercetin, whereas secretion was inhib
ited only at higher concentrations of inhibitor. Moreover, inhibition
of the activation of MAP kinase and release of arachidonic acid were c
losely correlated. This and previous findings suggested that release o
f arachidonic acid was attributable to the regulation of cytosolic PLA
(2) by MAP kinase (for activation of PLA(2)) and Ca2+ for association
of PLA(2) with the membrane), whereas release of hexosaminidase was re
gulated primarily by Ca2+ and protein kinase C.