STABLE EXPRESSION OF HUMAN KV1.3 POTASSIUM CHANNELS RESETS THE RESTING MEMBRANE-POTENTIAL OF CULTURED-MAMMALIAN-CELLS

A cDNA clone encoding the human Kv1.3 potassium channel was stably exp ressed at high levels in a Chinese hamster ovary (CHO) cell line. The expressed currents strongly resemble those recorded from Xenopus oocyt es injected with Kv1.3 cRNA, or from resting human T lymphocytes. One function ascribed to Kv1.3 in T lymphocytes is to stabilize the membra ne potential, thereby regulating the Ca2+ signalling critical for mito genic stimulation. In agreement with this hypothesis, we find that the heterologous expression of human Kv1.3 resets the resting potential o f CHO cells, setting it to the threshold of activation of Kv1.3. An in hibitor of Kv1.3, margatoxin, depolarized transfected CHO cells to the potential of non-transfected cells. The combination of a steep voltag e-dependence of activation with slow and incomplete inactivation appea rs to confer the ability of the Kv1.3 channel to 'clamp' the V-m of it s host cells within a narrow range.