Ca2+-sensitive regulation of E-type Ca2+ channel activity depends on an arginine-rich region in the cytosolic II-III loop.
Ca2+-dependent regulation of L-type and P/Q-type Ca2+ channel activity is an important mechanism to control Ca2+ entry into excitable cells. Here we addressed the question whether the activity of E-type Ca2+ channels can also be controlled by Ca2+. Switching from Ba2+ to Ca2+ as charge carrier increased within 50 s, the density of currents observed in HEK-293 cells expressing a human Cav2.3d subunit and slowed down the inactivation kinetics. Furthermore, with Ca2+ as permeant ion, recovery from inactivation was accelerated, compared to the recovery process recorded under conditions where the accumulation of [Ca2+]i was prevented. In a Ba2+ containing bath solution the Ca2+-dependent changes of E-type channel activity could be induced by dialysing the cells with 1 micro m free [Ca2+]i suggesting that an elevation of [Ca2+]i is responsible for these effects. Deleting 19 amino acids in the intracellular II-III linker (exon 19) as part of an arginine-rich region, severely impairs the Ca2+ responsiveness of the expressed channels. Interestingly, deletion of an adjacent homologue arginine-rich region activates channel activity but now independently from [Ca2+]i. As a positive feedback-regulation of channel activity this novel activation mechanism might determine specific biological functions of E-type Ca2+ channels.
Leroy
Jérôme
J
Institute of Neurophysiology, Institute of Vegetative Physiology, University of Cologne, Robert-Koch-Strasse 39, D-50931 Köln, Germany.
Pereverzev
Alexey
A
Vajna
Rolf
R
Qin
Ning
N
Pfitzer
Gabriele
G
Hescheler
Jürgen
J
Malécot
Claire O
CO
Schneider
Toni
T
Klöckner
Udo
U
D001120:Arginine / Q000737:chemistry; D001464:Barium / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004622:Embryo, Mammalian; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009154:Mutation; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D014162:Transfection
D015220:Calcium Channels; D002614:Chelating Agents; D021122:Protein Subunits; D001464:Barium; D004533:Egtazic Acid; D001120:Arginine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium