Cloning and functional expression of a voltage-gated calcium channel α1 subunit from jellyfish

Voltage-gated Ca2+ channels in vertebrates comprise at least seven molecular subtypes, each of which produces a current with distinct kinetics and pharmacology. Although several invertebrate Ca2+ channel cu, subunits have also been cloned, their functional characteristics remain unclear, as heterologous expression of a full-length invertebrate channel has not previously been reported. We have cloned a cDNA encoding the cu, subunit of a voltage-gated Ca2+ channel from the scyphozoan jellyfish Cyanea capillata, one of the earliest existing organisms to possess neural and muscle tissue. The deduced amino acid sequence of this subunit, named CyCa alpha(1), is more similar to vertebrate L-type channels (alpha(1S), alpha(1C), and alpha(1D)) than to non-1-type channels (alpha(1A), alpha(1B), and alpha(1E)) or low voltage-activated channels (alpha(1G)) Expression of CyCa alpha(1) in Xenopus oocytes produces a high voltage-activated Ca2+ current that, unlike vertebrate L-type currents, is only weakly sensitive to 1,4-dihydropyridine or phenylalkylamine Ca2+ channel blockers and is not potentiated by the agonist S(-)-BayK: 8644. In addition, the channel is less permeable to Ba2+ than to Ca2+ and is more permeable to Sr2+. CyCa alpha(1) thus represents an ancestral L-type alpha(1) subunit with significant functional differences from mammalian L-type channels.