Phosphorylation and spatiotemporal distribution of KW8 (NDRF/NeuroD2), a NeuroD family basic helix-loop-helix protein.

Abstract KW8, a NeuroD family basic helix–loop–helix protein, was initially cloned during the course of screening for the genes related to long term potentiation in rat hippocampal slice. Its homologue NDRF/NeuroD was also reported. In this report its phosphorylation and spatiotemporal distribution was studied. KW8 was expressed not only during embryonic and neonatal periods but also in adults. In adult, KW8 was expressed only in brain tissues, such as the cerebral cortex, hippocampus and cerebellum. Immunohistological studies revealed that KW8 was localized in the nuclei of neurons. On immunoblotting of rat brain tissue, COS-1 cells and Neuro2A cells overexpressing KW8, this protein was detected as several diffuse bands. Alkaline phosphatase treatment reduced the molecular weights of these bands. Metabolic labeling with 32 Pi in COS-1 cells confirmed that the KW8 protein was phosphorylated in vivo. Some of the physiological functions of KW8 might be regulated by this phosphorylation. In yeast, the GAL4 fusion protein containing the C-terminal region of KW8 activated transcription of the reporter gene, suggesting that KW8 had transcriptional activity.