In this study, we examined the role of PKC in the differentiation of multipotential neural precursor cells (NPCs). We found that the NPCs expressed PKCα,β2,δ,ε,ζ and low levels of PKCγ. The PKC activator, PMA, selectively increased the number of astrocytes, whereas it decreased the generation of neurons and oligodendrocytes. Similarly, overexpression of PKCε increased the differentiation of astrocytes and a PKCεKD mutant abolished PMA effect. PMA phosphorylates PKCε on serine 729. Using a PKCεS729A mutant, we found that the phosphorylation of PKCε on serine 729 was essential for the differentiation of astrocytes induced by PMA. To delineate the mechanisms involved in PMA and PKCε effects, we examined the expression of Notch1, which has been associated with astrocytic differentiation. We found that PMA and PKCε induced a large increase in Notch1 expression and the PKCεS729A mutant abolished PMA effect. Moreover, the PKCεS729A mutant also inhibited the effect of CNTF on astrocytic differentiation and Notch 1 expression. Finally, Notch1 mediated the effect of PMA on astrocytic differentiation, since the γ-secretase inhibitor L-685,458, and Notch1 silencing abolished PMA effect. Our data suggest an important role of PKCε in astrocytic differentiation and implicate Notch1 as a possible mediator of this effect.
- Neural precursor cells