The MAP Kinase Phosphatase MKP-1 Modulates Neurogenesis via Effects on BNIP3 and Autophagy

Inherited and acquired defects in neurogenesis contribute to neurodevelopmental disorders, dysfunctional neural plasticity, and may underlie pathology in a range of neurodegenerative conditions. Mitogen-activated protein kinases (MAPKs) regulate the proliferation, survival, and differentiation of neural stem cells. While the balance between MAPKs and the family of MAPK dual-specificity phosphatases (DUSPs) regulates axon branching and synaptic plasticity, the specific role that DUSPs play in neurogenesis remains unexplored. In the current study, we asked whether the canonical DUSP, MAP Kinase Phosphatase-1 (MKP-1), influences neural stem cell differentiation and the extent to which DUSP-dependent autophagy is operational in this context. Under basal conditions, Mkp-1 knockout mice generated fewer doublecortin (DCX) positive neurons within the dentate gyrus (DG) characterized by the accumulation of LC3 puncta. Analyses of wild-type neural stem cell (NSC) differentiation in vitro revealed increased Mkp-1 mRNA expression during the initial 24-h period. Notably, Mkp-1 KO NSC differentiation produced fewer Tuj1-positive neurons and was associated with increased expression of the BCL2/adenovirus E1B 19-kD protein-interacting protein 3 (BNIP3) and levels of autophagy. Conversely, Bnip3 knockdown in differentiated Mkp-1 KO NSCs reduced levels of autophagy and increased neuronal yields. These results indicate that MKP-1 exerts a pro-neurogenic bias during a critical window in NSC differentiation by regulating BNIP3 and basal autophagy levels.