Modulating Modulation: Crosstalk Between Regulatory Pathways of Presynaptic Calcium Channels

Proposed transmembrane topology of the calcium channel α₁ subunit, illustrating target sites for the PKC-dependent phosphorylation, syntaxin binding, and G protein-dependent modulation. A. The sites of action of PIP₂and PKA remain to be identified, and it remains possible that their effects are mediated by interactions with one of the ancillary calcium channel subunits.B. Crosstalk between regulatory pathways converging on presynaptic calcium channels. Inhibitory (red) and stimulatory (green) interactions are shown.