SEQUENTIAL INDUCTION OF 5-LIPOXYGENASE GENE-EXPRESSION AND ACTIVITY IN MONO-MAC-6 CELLS BY TRANSFORMING GROWTH-FACTOR-BETA AND 1,25-DIHYDROXYVITAMIN-D3
M. Brungs et al., SEQUENTIAL INDUCTION OF 5-LIPOXYGENASE GENE-EXPRESSION AND ACTIVITY IN MONO-MAC-6 CELLS BY TRANSFORMING GROWTH-FACTOR-BETA AND 1,25-DIHYDROXYVITAMIN-D3, Proceedings of the National Academy of Sciences of the United Statesof America, 92(1), 1995, pp. 107-111
5-Lipoxygenase (5-LO; EC 1.13.11.34) activity in the human monocytic c
ell line Mono Mac 6 was upregulated by combined treatment with transfo
rming growth factor beta 1 (TGF-beta) and 1,25-dihydroxyvitamin D-3 (V
D3). In undifferentiated cells, 5-LO enzyme activity was undetectable.
After the addition of TGF-beta plus VD3, the activity of intact cells
was 800 ng per 10(6) cells-500 times more than the assay detection li
mit. Also 5-LO protein and mRNA expression were induced >128-fold and
64-fold, respectively, as compared to undifferentiated cells. Both TGF
-beta and VD3 were required for these prominent responses. Either agen
t alone gave small amounts of 5-LO protein and mRNA but very low 5-LO
activities. After the addition of TGF-beta and VD3, the induction of 5
-LO protein was obvious after 1 day, but the increase in activity was
delayed and did not appear until the second day. Pretreatment of cells
with TGF-beta or VD3 alone for 2 days led to 5-LO protein expression
but very low enzyme activity. Addition of the lacking second inducer w
as required for full induction of 5-LO protein expression and for upre
gulation of enzyme activity, partial purification of 5-LO from Mono Ma
c 6 cells and recombination with soluble cellular proteins from differ
ent sources indicated the presence of cytosolic factors that affect th
e activity of 5-LO.