Overexpression of neuronal pentraxin 1 is involved in neuronal death evoked by low K+ in cerebellar granule cells

Mature cerebellar granule cells in culture die by a process that requires n ew RNA and protein synthesis when deprived of depolarizing concentrations o f potassium. We investigated gene expression during the early phase of the cell death program evoked by potassium deprivation, Using a differential ge ne display technique, we isolated a cDNA that was increased by potassium de privation. This cDNA was homologous to the 3' mRNA end of neuronal pentraxi n 1 (NP1), a gene encoding a secreted glycoprotein whose expression is rest ricted to the nervous system. Reverse-Northern and Northern blot analyses c onfirmed that treatment with low potassium induces overexpression of NP1 mR NA, with a subsequent increase in NP1 protein levels. Time-course studies i ndicated that overexpression of NP1 protein reaches a maximum after 4 h of exposure to potassium deprivation and 4 h before significant cell death. In cubation of cerebellar granule cells with an antisense oligodeoxyribonucleo tide directed against NP1 mRNA reduced low potassium-evoked NP1 protein lev els by 60% and attenuated neuronal death by 50%, whereas incubation with th e corresponding sense oligodeoxyribonucleotide was ineffective. Furthermore , acute treatment with lithium significantly inhibited both overexpression of NP1 and cell death evoked by low potassium. These results indicate that NP1 is part of the gene expression program of apoptotic cell death activate d by nondepolarizing culture conditions in cerebellar granule cells.