New Insight into the Involvement of Large-Conductance Calcium-Activated-Potassium-Channel(BK) in Cell Viability: Pathophysiological Implications in Neuromuscular Disorders

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The large conductance Ca2+-activated K+-channel (BK) is involved in several pathophysiological conditions including periodic paralysis (PP) and myotonia. Acetazolamide (ACTZ) a carbonic anhydrase inhibitor used in these conditions, acts targeting BK in PP. Here we investigated the involvement of BK channel in neuronal viability (SH-SY5Y cell) by combining patch-clamp technique and cell proliferation assays. We performed these measurements in the presence or absence of the selective BK channel blocker Iberiotoxin(IbTX) (10-400x10−9M), the unselective K+-channels blocker Tetraethylammonium (TEA) (0.01-1x10−3M), and the BK channel openers NS1619 (10-100x10−5M) and ACTZ (0.1-200x10−6M). Patch-clamp recordings showed that at +30mV (Vm) IbTX and TEA reduced whole cell K+-current in a concentration -dependent manner with an Imax of −46% and −90% respectively. NS1619 enhanced K+-current of +141% at −10mV (Vm). Acetazolamide, that in muscle acts as a BK opener, in neurons caused a concentration-dependent block of K+-current at +30mV(Vm) with an IC50 of 1.73x10−7M an Imax of −40% (slope=0.37) (Number of patches=12). These drugs exert their effects also on neuronal cell viability, enhancing it: IbTX showed a maximal proliferative effect (MPE) of +46% at 10−8M concentration, reducing it at higher concentrations; TEA showed a concentration-dependent increase of cell proliferation with a MPE of +34% at a 10−4M concentration; NS1619 and ACTZ showed a MPE of +181.6% at 5x10−5M and +135% at 100x10−6M concentration respectively. Staurosporine (STS) (2x10-6M), a broad spectrum protein kinases inhibitor, prevented the IbTX and TEA proliferative action. These results suggest that BK channel may play a role in the regulation of neuronal viability through an intracellular pathway that involves STS-sensitive protein kinases. These findings may have relevance in the cellular repair mechanisms in the neuromuscular disorders. Supported by Telethon GG14096.