ATP inhibition of a mouse brain large-conductance K+ (mslo) channel variant by a mechanism independent of protein phosphorylation

1. We investigated the effect of ATP in the regulation of two closely relat ed cloned mouse brain large conductance calcium- and voltage-activated pota ssium (BK) channel alpha-subunit variants, expressed in human embryonic kid ney (HEK 293) cells, using the excised inside-out configuration of the patc h-clamp technique. 2. The mB2 BK channel alpha-subunit variant expressed alone was potently in hibited by application of ATP to the intracellular surface of the patch wit h an IC50 of 30 mu M. The effect of ATP was largely independent of protein phosphorylation events as the effect of ATP was mimicked by the non-hydroly sable analogue 5'-adenylylimidodiphosphate (AMP-PNP) and the inhibitory eff ect of ATP gamma S was reversible. 3. In contrast, under identical conditions, direct nucleotide inhibition wa s not observed in the closely related mouse brain B41 channel alpha-subunit variant mbr5. Furthermore, direct nucleotide regulation was not observed w hen mB2 was functionally coupled to regulatory beta-subunits. 4. These data suggest that the mB2 alpha-subunit splice variant could provi de a dynamic link between cellular metabolism and cell excitability.