Stimulation of protein kinase C recruits covert calcium channels in Aplysia bag cell neurons

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Abstract
The modulation of voltage-activated calcium currents by protein kinases provides excitable cells with a mechanism for regulating their electrical behaviour1–7. At the single channel level, modulation of calcium current has, to date, been characterized only in cardiac muscle, where β-adrenergic agonists, acting through cyclic AMP-dependent protein kinase, enhance the calcium current by increasing channel availability and opening3,8–12. We now report that enhancement of calcium current in the peptidergic bag cell neurons of Aplysia by protein kinase C (ref. 13) occurs through a different mechanism, the recruitment of a previously covert class of calcium channel. Under control conditions, bag cell neurons contain only one class of voltage-activated calcium channel with a conductance of ∼12 pS. After exposure to agents that activate protein kinase C, these neurons also express a second class of calcium channel with a different unitary conductance (∼24pS) that is never seen in untreated cells.