Coexpression of hslo-beta with hslo-alpha subunits gives rise to Ca2+-activated potassium currents with a much increased calcium and/or voltage sensitivity.
The cloning and coexpression of the human hslo-beta subunit with the alpha subunit demonstrates that the beta subunit significantly increases the calcium and voltage sensitivity of Ca2+-activated K+ channels.
We have cloned and expressed a Ca(2+)-activated K+ channel beta-subunit from human brain. The open reading frame encodes a 191-amino acid protein possessing significant homology to a previously described subunit cloned from bovine muscle. The gene for this subunit is located on chromosome 5 at band q34 (hslo-beta). There is no evidence for alternative RNA splicing of this gene product. hslo-beta mRNA is abundantly expressed in smooth muscle, but expression levels are low in most other tissues, including brain. Brain subregions in which beta-subunit mRNA expression is relatively high are the hippocampus and corpus callosum. The coexpression of hslo-beta mRNA together with hslo-alpha subunits in either Xenopus oocytes or stably transfected HEK 293 cells give rise to Ca(2+)-activated potassium currents with a much increased calcium and/or voltage sensitivity. These data indicate that the beta-subunit shows a tissue distribution different to that of the alpha-subunit, and in many tissues there may be no association of alpha-subunits with beta-subunits. These beta-subunits can play a functional role in the regulation of neuronal excitability by tuning the Ca2+ and/or the voltage dependence of alpha-subunits.
Tseng-Crank et al. (Tue,) reported a other. hslo-beta coexpression vs. hslo-alpha alone was evaluated on Voltage and calcium sensitivity of KCa channels. Coexpression of hslo-beta with hslo-alpha subunits gives rise to Ca2+-activated potassium currents with a much increased calcium and/or voltage sensitivity.