J. Hoppe et al., DIFFERENTIAL ACTIVATION BY PLATELET-DERIVED GROWTH FACTOR-BB OF MITOGEN-ACTIVATED PROTEIN-KINASES IN STARVED OR NONSTARVED AKR-2B FIBROBLASTS, Journal of cellular physiology, 161(2), 1994, pp. 342-350
More than 90% of serum-deprived (starved) AKR-2B mouse fibroblasts are
stimulated to divide by the addition of platelet-derived growth facto
r (PDCF)-BB. In density-arrested (nonstarved) cells, PDGF-BB affords p
rotection from cell death without stimulation of cell division. In bot
h cultivation conditions the cells express similar amounts of PDGF bet
a-receptors and the receptor kinase activity was identical as judged b
y its autophosphorylation capacity. Three signaling pathways were stud
ied in detail: 1) Phospholipase C-gamma (PLC-gamma) and [Ca2+](i) incr
ease, 2) activation of the phosphatidylinositol-3 kinase (PI-3 kinase)
, and 3) activation of mitogen activated kinases I and II (MAP kinases
I and II). There was no difference in starved or nonstarved cells reg
arding PLC-gamma activation, increase of [Ca2+](i), and stimulation oi
PI-3 kinase activity. But most remarkably the activation of MAP-I was
largely suppressed in nonstarved cells. The implications of these sig
naling pathways in cell protection or cell division are discussed. (C)
1994 Wiley-Liss, Inc.