Cyi. Yan et La. Greene, PREVENTION OF PC12 CELL-DEATH BY N-ACETYLCYSTEINE REQUIRES ACTIVATIONOF THE RAS PATHWAY, The Journal of neuroscience, 18(11), 1998, pp. 4042-4049
We have shown that N-acetylcysteine (NAC) promotes survival of sympath
etic neurons and pheochromocytoma (PC12) cells in the absence of troph
ic factors. This action of NAC was not related to its antioxidant prop
erties or ability to increase intracellular glutathione levels but was
instead dependent on ongoing transcription and seemed attributable to
the action of NAC as a reducing agent. Here, we investigate the mecha
nism by which NAC promotes neuronal survival. We show that NAG activat
es the Ras-extracellular signal-regulated kinase (ERK) pathway in PC12
cells. Pas activation by NAC seems necessary for survival in that it
is unable to sustain serum-deprived PC12 MM17-26 cells constitutively
expressing a dominant-negative farm of Ras. Promotion of PC12 cell sur
vival by NAC is totally blocked by PD98059, an inhibitor of the ERK-ac
tivating MAP kinase/ERK kinase, suggesting a required role for ERK act
ivation in the NAC mechanism. In contrast, LY294002 and wortmannin, in
hibitors of phosphatidylinositol 3-kinase (PI3K) that partially block
NGF-promoted PC12 cell survival, have no effect on prevention of death
by NAG. We hypothesized previously that the ability of NAC to promote
survival correlates with its antiproliferative properties. However, a
lthough NAC does not protect PC12 MM17-26 cells from loss of trophic s
upport, it does inhibit their capacity to synthesize DNA. Thus, the an
tiproliferative effect of NAG does not require Ras activation, and inh
ibition of DNA synthesis is insufficient to mediate NAG-promoted survi
val. These findings highlight the role of Ras-ERK activation in the me
chanism by which NAC prevents neuronal death after loss of trophic sup
port.