Molecular and functional analysis of ATP-sensitive K^+ channel on the nuclear envelope

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This study was undertaken to test whether ATP-sensitive K^+ (K_<ATP> ) channel exists on the nuclear envelope of cardiac cells and to determine the functional molecules and physiological roles of K_<ATP> channel on the nuclear envelope. Using binding assay of glibenclamide-BODIPY-FL to sulfonylurea receptor we tested the existence of K_<ATP> channel on the nuclear envelope. We could observe the binding of glibenclamide-BODIPY-FL colocalized with Hoechst, a nuclear marker, using confocal microscopy, suggesting the existence of sufonylurea receptor on the nuclear envelope of cardiomyocytes. The single channel activity was recorded from the nuclear envelope of isolated nuclei using patch clamp techniques. Although several kinds of single channel activity could be recorded from the nuclear envelope, the channel activity was not influenced by glibenclamide, tolbutamide, or pinacidil. Nuclear Ca^<2+> signal was measured using confocal microscopy and the Ca^<2+> sensitive fluorescence dye Fluo-3/AM. Neither glibenclamide nor tolbutamide affected Ca^<2+> concentration in the nuclear envelope. Thus, even if K_<ATP> channel exists on the nuclear envelope of cardiac cells, the density or physiological significance of the channel may not be so large.