Honeybee CaV4 Has Distinct Permeation, Inactivation, and Pharmacology from Homologous NaV Channels

DSC1, a Drosophila channel with sequence similarity to the voltage-gated sodium channel (NaV), was identified over 20 years ago. This channel was suspected to function as a non-specific cation channel with the ability to facilitate the permeation of calcium ions (Ca2+). A honeybee channel homologous to DSC1 was recently cloned and shown to exhibit strict selectivity for Ca2+, while excluding sodium ions (Na+), thus defining a new family of Ca2+ channels, known as CaV4. In this study, we characterize CaV4, showing that it exhibits an unprecedented type of inactivation, which depends on both an IFM motif and on the permeating divalent cation, like NaV and CaV1 channels, respectively. CaV4 displays a specific pharmacology with an unusual response to the alkaloid veratrine. It also possesses an inactivation mechanism that uses the same structural domains as NaV but permeates Ca2+ ions instead. This distinctive feature may provide valuable insights into how voltage- and calcium-dependent modulation of voltage-gated Ca2+ and Na+ channels occur under conditions involving local changes in intracellular calcium concentrations. Our study underscores the unique profile of CaV4 and defines this channel as a novel class of voltage-gated Ca2+ channels.