Seizures increase importin-b1 expression in NG2+ cells in the rat hippocampus.

Importins, also called karyopherins, belong to a large family of proteins involved in cytoplasm-to-nucleus transport. Transport machinery generally involves a complex formed by two different importin subtypes (α and β). Both α and β importins are expressed in the brain, and their expression and localization is regulated by physiological neuronal activity. Little is known about regulation of importin expression in brain pathological conditions. Here we studied the expression of importin β1 (impβ1) in the rat hippocampus after acute and chronic seizures induced by the glutamate agonist kainic acid (KA). The overall content of impβ1 mRNA and protein-did not change after acute KA seizures. However, acute KA seizures rapidly induced the translocation of impβ1 protein from the cytoplasm to the nucleus in pyramidal CA1 neurons. KA-induced impβ1 translocation was prevented by the NMDA (N-methyl-D-aspartic acid) receptor blocker MK-801. After chronic seizures, the overall levels of impβ1 mRNA a...