Implication of Akt-dependent Prp19 alpha/14-3-3beta/Cdc5L complex formation in neuronal differentiation

PRP19alpha and CDC5L are major components of the active spliceosome. However, their association process is still unknown. Here, we demonstrated that PRP19 alpha/14-3-3beta/CDC5L complex formation is regulated by Akt during nerve growth factor (NGF)-induced neuronal differentiation of PC12 cells. Analysis of PRP19 alpha mutants revealed that the phosphorylation of PRP19 alpha at Thr 193 by Akt was critical for its binding with 14-3-3beta to translocate into the nuclei and for PRP19 alpha/14-3-3beta/CDC5L complex formation in neuronal differentiation. Forced expression of either sense PRP19 alpha or sense 14-3-3beta RNAs promoted NGF-induced neuronal differentiation, whereas down-regulation of these mRNAs showed a suppressive effect. The nonphosphorylation mutant PRP19 alpha T193A lost its binding ability with 14-3-3beta and acted as a dominant-negative mutant in neuronal differentiation. These results imply that Akt-dependent phosphorylation of PRP19 alpha at Thr193 triggers PRP19 alpha/14-3-3beta/CDC5L complex formation in the nuclei, likely to assemble the active spliceosome against neurogenic pre-mRNAs.