MODULATION OF THE SKELETAL-MUSCLE SODIUM-CHANNEL ALPHA-SUBUNIT BY THEBETA(1)-SUBUNIT

Co-expression of cloned sodium channel beta(1)-subunit with the rat sk eletal muscle-subunit (alpha(mu I)) accelerated the macroscopic curren t decay, enhanced the current amplitude, shifted the steady state inac tivation curve to more negative potentials and decreased the time requ ired for complete recovery from inactivation. Sodium channels expresse d from skeletal muscle mRNA showed a similar behaviour to that observe d from alpha(mu I)/beta(1), indicating that beta(1) restores 'physiolo gical' behaviour. Northern blot analysis revealed that the Na+ channel beta(1)-subunit is present in high abundance (about 0.1%) in rat hear t, brain and skeletal muscle, and the hybridization with untranslated region of the 'brain' beta(1) cDNA to skeletal muscle and heart mRNA i ndicated that the diffferent Na+ channel alpha-subunits in brain, skel etal muscle and heart may share a common beta(1)-subunit.