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 nervous system tissue, yet the role of these enzymes in the modulation of neuronal excitability is unknown. Patch-clamp studies of an Aplysia voltage-gated cation channel now demonstrate that a tyrosine phosphatase 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 phosphatase occurs at the onset of a prolonged change in the excitability of Aplysia bag cell neurons.