ENHANCEMENT OF BETA-ADRENERGIC-RECEPTOR ACTIVATION OF MAXI-K+ CHANNELS BY GM1 GANGLIOSIDE

In freshly dispersed guinea-pig taenia coli myocytes, beta-adrenergic receptor agonist increased the open probability (p(o)) of the maxi-Kchannels through the G-protein, G. Subunit B of cholera toxin (0.1 nM) suppressed the ISO-induced increase of p(o) of maxi-K-s+ channels but did not affect that induced by forskolin. Brief (20 min) treatment of the myocytes with GM1 ganglioside (GM1, 0.1-1.0 mu M) enhanced the ef fectiveness of ISO-induced increase of p(o). This effect was blocked b y 0.5% trypsin, which is known to prevent the incorporation of exogene ous GM1 into the membrane. The effect of GM1 was not shared by GM2 and GM3 gangliosides. These results suggest that the membrane-bound endog eneous GM1 may participate in the regulation of cellular response to b eta-adrenergic agents. (C) 1994 Academic Press, Inc.