MODE-SWITCHING OF A VOLTAGE-GATED CATION CHANNEL IS MEDIATED BY A PROTEIN KINASE-A REGULATED TYROSINE PHOSPHATASE

Tyrosine kinases and tyrosine phosphatases are abundant in central ner vous system tissue, yet the role of these enzymes in the modulation of neuronal excitability is unknown. Patch-clamp studies of an Aplysia v oltage-gated cation channel now demonstrate that a tyrosine phosphatas e endogenous to excised patches determines both the gating mode of the channel and the response of the channel to protein kinase A. Moreover , a switch in gating modes similar to that triggered by the phosphatas e occurs at the onset of a prolonged change in the excitability of Apl ysia bag cell neurons.