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Cross Talk Between Substance P and Melittin‐Activated Cellular Signaling Pathways in Rat Lactotroph‐Enriched Cell Cultures
Author(s) -
Mau Søren E.,
Vilhardt Hans
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.69020762.x
Subject(s) - nordihydroguaiaretic acid , protein kinase c , arachidonic acid , phospholipase c , phospholipase a2 , melittin , biology , phorbol , diacylglycerol kinase , biochemistry , phospholipase , microbiology and biotechnology , cell culture , tetradecanoylphorbol acetate , signal transduction , enzyme , peptide , genetics
We have investigated the possible interaction (cross talk) between the phospholipase A 2 (PLA 2 ) and inositol 1,4,5‐trisphosphate/protein kinase C (PKC) signaling pathways in rat lactotroph‐enriched cell cultures. Melittin, a bee venom peptide, stimulated release of [ 3 H]‐arachidonic acid ([ 3 H]AA) from [ 3 H]AA‐labeled enriched lactotrophs in a dose‐dependent manner. Moreover, melittin and exogenous AA induced a redistribution of PKC catalytic activity and PKCα and β immunoreactivity from the soluble to the particulate fraction in resting and substance P (SP)‐stimulated cells. Mellitin had no effect on phospholipase C (PLC) activity. Pretreatment of cell cultures with the PLA 2 inhibitors quinacrine and aristolochic acid resulted in a dose‐dependent inhibition of melittin‐stimulated PKC isozyme translocation as did the inhibitor of lipoxygenase, nordihydroguaiaretic acid, whereas the cyclooxygenase inhibitor indomethacin had no effect. SP and the phorbol ester 12‐ O ‐tetradecanoylphorbol 13‐acetate (TPA) dose‐dependently increased levels of [ 3 H]AA released from cells. Pretreatment of cell cultures with quinacrine reduced the effect of SP on [ 3 H]AA formation. After long‐term treatment (24 h) of cells with TPA, the effect of TPA on [ 3 H]AA production was not different from control, whereas SP still displayed [ 3 H]AA‐releasing abilities although not at full scale. Pretreatment of cells with thapsigargin, U 73122, methoxyverapamil, and RHC 80267, an inhibitor of diacylglycerol lipase, all resulted in reduced SP‐stimulated [ 3 H]AA liberation. Treatment of cell cultures with pertussis toxin (PTX) reduced the release of [ 3 H]AA induced by SP, whereas PTX had no effect on SP‐stimulated generation of 3 H‐inositol phosphates. On the basis of these results, it is concluded that (1) the PLA 2 pathways interfere with the phosphoinositide‐PLC signaling system at the level of PKC isozymes α and β, the product responsible for this interaction being either AA or a metabolite produced by the action of lipoxygenase; (2) SP and TPA are able to activate the PLA 2 pathway at a level at or beyond PLA 2 , and this effect is mediated, in part, through PKCα and β species and (for SP) intracellular Ca 2+ recruited from internal stores as well as from external sources; and (3) SP also activates PLA 2 through a PTX‐sensitive pathway distinct from the one coupled to phosphoinositide‐PLC, which is PTX insensitive.