ERK1/2 inhibition increases dopamine release from differentiated PC12 cells.

The release of dopamine (DA) is one of the main steps in the control of neuronal functioning and all CNS. It was demonstrated that many factors such as protein kinases and synaptic proteins are tightly involved in the regulation of DA secretion, but the data are contradictory. Here we analysed an effect of ERK1/2 inhibition on DA secretion from differentiated PC12 cells and evaluated the correlation between the activity of kinases/synaptic proteins and the level of released DA. PC12 cells were differentiated by NGF for 6 days. On the 7th day the cells were incubated for 1, 2 and 4 h with 10µM U0126. Obtained data demonstrated a significant accumulation of DA in the media after 4 h incubation with U0126 that accompanied with upregulation of PKG activity. Analysis of exocytosis proteins demonstrated decreased phosphorylation level of synapsin I and content of SNAP25. Taken together our data proposed an inhibitory role of ERK1/2 in the regulation of catecholamine secretion and demonstrated that balance between PKG and ERK1/2 activity could have a substantial impact on the regulation of DA release from the cells.

[Role p53 and MAPK signaling integration in the regulation of PC12 cell neural differentiation].

p53 is a transcription factor and then induced by cellular stress regulates ageing, cell cycle arrest and apoptosis. Published data also demonstrated that p53 participates in the regulation of neuronal differentiation. However, the data concerning the mechanisms of neuronal differentiation by p53 is very limited. In the present work we have studied a role and mechanisms of p53 activated by Nutlin-3 in the differentiation of PC12 cells. In our experiments Nutlin-3 stimulated the cell differentiation by significantly increasing of the neuritis upgrowth and upregulation of tyrosine hydroxylase (TH) expression, the catecholamine main rate-limited ferment. We have also analyzed MAPK signaling cascade that tightly participate in the neuronal differentiation. Obtained data demonstrated that activation of p53 by Nutlin-3 injections increased the activity of cRaf and ERK1/2, as well as transcription factor CREB, which is one of the targets for ERK pathway and regulates transcription of TH. Thus, we demonstrated that p53 activation lead to increased differentiation of PC12 cells and this effect is mediated by cRaf/ERK/CREB pathway.