Transient and big are key features of an invertebrate T-type channel (LCav3) from the central nervous system of Lymnaea stagnalis.
Here we describe features of the first non-mammalian T-type calcium channel (LCa(v)3) expressed in vitro. This molluscan channel possesses combined biophysical properties that are reminiscent of all mammalian T-type channels. It exhibits T-type features such as "transient" kinetics, but the "tiny" label, usually associated with Ba(2+) conductance, is hard to reconcile with the "bigness" of this channel in many respects. LCa(v)3 is 25% larger than any voltage-gated ion channel expressed to date. It codes for a massive, 322-kDa protein that conducts large macroscopic currents in vitro. LCa(v)3 is also the most abundant Ca(2+) channel transcript in the snail nervous system. A window current at typical resting potentials appears to be at least as large as that reported for mammalian channels. This distant gene provides a unique perspective to analyze the structural, functional, drug binding, and evolutionary aspects of T-type channels.
Senatore
Adriano
A
Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Spafford
J David
JD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002121:Calcium Channel Blockers / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002490:Central Nervous System / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008195:Lymnaea / Q000033:anatomy & histology / Q000378:metabolism; D020748:Mibefradil / Q000378:metabolism; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010802:Phylogeny; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D020748:Mibefradil; D009532:Nickel