J. Biol. Chem., Vol. 265, Issue 12, 6642-6649, 04, 1990
Positive and negative regulation of a tumor necrosis factor response in melanoma cells
SE Johnson and C Baglioni
Department of Biological Sciences, State University of New York, Albany 12222.
Tumor necrosis factor (TNF) elicits a wide variety of responses in target
cells by binding to cell surface receptors, but the signal transduced from
these receptors in unclear. We examined the role of two different second
messenger systems in the regulation of plasminogen activator inhibitor,
type 2 (PAI-2) induction by TNF in SK-MEL-109 melanoma cells. Synthesis of
PAI-2 and transcription of its mRNA could be induced by a protein kinase C
(PKC) activator, phorbol myristate acetate. In addition, induction of PAI-2
synthesis by TNF was blocked by two PKC inhibitors, staurosporine and
1-(5-isoquinolinesulfonyl)-2- methylpiperazine dihydrochloride. The
inhibitor of cyclic nucleotide- dependent protein kinases,
N-[2-(methylamino)-ethyl]-5-isoquinoline sulfonamide dihydrochloride, was
much less effective in decreasing PAI- 2 synthesis. Staurosporine and
1-(5-isoquinolinesulfonyl)-2- methylpiperazine dihydrochloride also
inhibited both TNF- and phorbol myristate acetate-induced PAI-2 mRNA
accumulation. We measured the binding of 3H-labeled phorbol dibutyrate to
membrane and cytosol fractions of TNF-treated SK-MEL-109 cells and found a
transient redistribution of 3H-labeled phorbol dibutyrate binding from
cytosol to membrane fractions in response to TNF. In contrast to the
positive regulation by PKC in promoting TNF-induced PAI-2 synthesis cAMP
inhibited this response. Pretreatment of cells with agents that raise
intracellular cAMP levels completely abolished TNF-induced PAI-2 synthesis.
Addition of cAMP-elevating agents during TNF induction could also block
PAI-2 synthesis. PAI-2 mRNA accumulation in response to TNF was inhibited,
but not completely abolished, by cAMP-elevating agents, suggesting that
cAMP also exerted its inhibitory effect at the translation level. The
positive regulation of a TNF response by PKC and its negative modulation by
cAMP may provide a means for intracellular coordination of signals from
interacting extracellular factors in regulating TNF responses in different
target cells.