迷走,舌下神経核における JNK isoform の発現の差異

Abstract

Mitogen-activated protein kinases (MAPKs)are important mediators of signal transduction from the cell surface to the nucleus. c-Jun amino-terminal kinase (JNK) is a member of the MAP kinase group. The JNK family of kinases is comprised of at least 3 isoforms, JNK 1, JNK 2 and JNK 3, and all of these kinases phosphorylate the transcription factor c-Jun in response to various stimulations. c-Jun is one of the earliest and most consistent markers for neurons that respond to nerve-fiber transection. It is reported that the dorsal motor nucleus of vagus nerve shows degenerative changes after axotomy while the hypoglossal nucleus shows regenerative changes. In order to elucidate c-Jun metabolism after axotomy, we investigated the expression of JNK 1, JNK 2 and JNK 3 mRNA and immunohistochemical expression of JNK 1, JNK 2 and JNK 3 protein following vagus and hypoglossal nerve transection. We found that JNK 1, JNK 2 and JNK 3 mRNA were positive in the cytoplasms of neuronal and microglial cells. JNK 1 and JNK 2 protein were distributed mainly in the cytoplasm of neurons and glial cells, while only the JNK 3 immunoreactivity was observed intensely in the nuclei of neuronal cells. These results indicate that the principal activity of JNKs in neurons is contributed largely by JNK 3 under both normal and axotomized conditions.