IMMUNOHISTOCHEMICAL LOCALIZATION OF 5 MEMBERS OF THE KV1 CHANNEL SUBUNITS - CONTRASTING SUBCELLULAR LOCATIONS AND NEURON-SPECIFIC CO-LOCALIZATIONS IN RAT-BRAIN

A large variety of potassium channels is involved in regulating integr ation and transmission of electrical signals in the nervous system. Di fferent types of neurons, therefore, require specific patterns of pota ssium channel subunit expression and specific regulation of subunit co assembly into heteromultimeric channels, as well as subunit-specific s orting and segregation. This was investigated by studying in detail th e expression of six different alpha-subunits of voltage-gated potassiu m channels in the rat hippocampus, cerebellum, olfactory bulb and spin al cord, combining in situ hybridization and immunocytochemistry. Spec ific polyclonal antibodies were prepared for five alpha-subunits (K(v) 1.1, K(v)1.2, K(v)1.3, K(v)1.4, K(v)1.6) of the Shaker-related subfami ly of rat K-v channels, which encode delayed-rectifier type and rapidl y inactivating A-type potassium channels. Their distribution was compa red to that of an A-type potassium channel (K(v)3.4), belonging to the Shaw-related subfamily of rat K-v channels. Our results show that the se K-v channel alpha-subunits are differentially expressed in rat brai n neurons. We did not observe in various neurons a stereotypical distr ibution of K-v channel alpha-subunits to dendritic and axonal compartm ents, but a complex differential subcellular subunit distribution. The different K-v channel subunits are targeted either to presynaptic or to postsynaptic domains, depending on neuronal cell type. Thus, distin ct combinations of K(v)1 alpha-subunits are co-localized in different neurons. The implications of these findings are that both differential expression and assembly as well as subcellular targeting of K-v chann el alpha-subunits may contribute to K-v channel diversity and thereby to presynaptic and postsynaptic membrane excitability.