MYOSIN LIGHT-CHAIN KINASE OCCURS IN BULLFROG SYMPATHETIC NEURONS AND MAY MODULATE VOLTAGE-DEPENDENT POTASSIUM CURRENTS

A polyclonal antibody against myosin light chain kinase (MLCK) of chic ken gizzard recognized a 130 kd peptide of bullfrog sympathetic gangli a as MLCK. MLCK immunoreactivity was confined to the neuronal cell bod y. A synthetic peptide corresponding to an inhibitory domain of MLCK ( Ala783-Gly804) Was applied intracellularly to isolated sympathetic neu rons during whole-cell recordings of ionic currents. The peptide inhib itor reversibly decreased M-type potassium current (I(M)) while not af fecting A-type or delayed rectifier-type potassium currents. Intracell ular application of an active fragment of MLCK enhanced I(M), whereas application of an inactive MLCK fragment did not. The results suggest that I(M) can be modulated by MLCK-catalyzed phosphorylation.