Activity-dependent subcellular localization of NAC1.

The expression of the transcriptional regulator NAC1 is increased in the nucleus accumbens of rats withdrawn from cocaine self-administration, and in vivo studies indicate that the up-regulation is a compensatory mechanism opposing the acute effects of cocaine. Both mammalian two-hybrid assay and punctate localization largely in the nucleus suggest NAC1 is a transcriptional regulator. However, in this report it is shown that in differentiated PC12 and Neuro2A cells, as well as in primary cortical neurons, NAC1 is diffusely expressed not only in the cell nucleus but also in cytoplasm. Blockade of spontaneous electrical activity by tetrodotoxin prevented the diffuse expression of NAC1, and depolarization with high potassium concentrations induced diffuse cellular localization in non-differentiating cells. The use of protein kinase C (PKC) inhibitors and activator, as well as the systematic mutation of potential PKC phosphorylation sites in NAC1, demonstrated that phosphorylation of residue S245 by PKC is a necessary event inducing diffuse NAC1 expression outside of the nucleus. These observations indicate a potential non-transcriptional role for NAC1 in the brain.