PKC delta in preeclamptic placentas promotes Bax dissociation from 14-3-3 zeta through 14-3-3 zeta phosphorylation

Abstract

Objective: We investigated placental apoptosis and the expression of and interactions between 14-3-3 and Bc1-2 family proteins during preeclampsia. In addition, we explored the mechanism of Bax dissociation from 14-3-3, hypothesizing that PKC-mediated phosphorylation of 14-3-3 results in dissociation of Bax from 14-3-3 proteins, and leads to apoptosis. Methods: Placental samples from 10 women with preeclampsia and 10 normotensive control patients were analyzed using M30-specific immunohistochemistry to assess placental apoptosis. Biochemical markers of cellular apoptosis, such as cleaved caspase-3, Bax, Bcl-2, 14-3-3, and PKC were followed by Western blotting. Interaction of 14-3-3 proteins with Bax and with PKC was assessed by immunoprecipitation. Results: M30-positive cells were widespread in the preeclamptic placentas. The levels of cleaved caspase-3, Bax, 14-3-3 zeta, phospho-(Ser)-14-3-3, and PKC delta were significantly higher in the preeclamptic placentas than in normal placentas. Preeclampsia was also associated with weaker interactions between 14-3-3 zeta and Bax and stronger interactions between 14-3-3 zeta and PKC delta. Conclusion: Our results suggest that PKC delta in preeclamptic placentas promotes Bax dissociation from 14-3-3 zeta through the phosphorylation of 14-3-3 zeta. This finding may at least in part explain the apoptosis-inducing activity of PKC delta, revealing the important role of PKC delta in the development of apoptosis-related diseases such as preeclampsia. (C) 2008 Elsevier Ltd. All rights reserved.