Molecular characterization of a two-domain form of the neuronal voltage-gated P/Q-type calcium channel alpha(1)2.1 subunit.
We characterized the neuronal two-domain (95kD-alpha(1)2.1) form of the alpha(1)2.1 subunit of the voltage-gated calcium channels using genetic and molecular analysis. The 95kD-alpha(1)2.1 is absent in neuronal preparations from CACNA1A null mouse demonstrating that alpha(1)2.1 and 95kD-alpha(1)2.1 arise from the same gene. A recombinant two-domain form (alpha(1AI-II)) of alpha(1)2.1 associates with the beta subunit and is trafficked to the plasma membrane. Translocation of the alpha(1AI-II) to the plasma membrane requires association with the beta subunit, since a mutation in the alpha(1AI-II) that inhibits beta subunit association reduces membrane trafficking. Though the alpha(1AI-II) protein does not conduct any voltage-gated currents, we have previously shown that it generates a high density of non-linear charge movements [Ahern et al., Proc. Natl. Acad. Sci. USA 98 (2001) 6935-6940]. In this study, we demonstrate that co-expression of the alpha(1AI-II) significantly reduces the current amplitude of alpha(1)2.1/beta(1a)/alpha(2)delta channels, via competition for the beta subunit. Taken together, our results demonstrate a dual functional role for the alpha(1AI-II) protein, both as a voltage sensor and modulator of P/Q-type currents in recombinant systems. These studies suggest an in vivo role for the 95kD-alpha(1)2.1 in altering synaptic activity via protein-protein interactions and/or regulation of P/Q-type currents.
Arikkath
Jyothi
J
Howard Hughes Medical Institute, Department of Physiology, University of Iowa College of Medicine, 400 Eckstein Medical Research Building, Iowa City, IA 52242-1101, USA.
Felix
Ricardo
R
Ahern
Christopher
C
Chen
Chien-Chang
CC
Mori
Yasuo
Y
Song
Inseon
I
Shin
Hee-Sup
HS
Coronado
Roberto
R
Campbell
Kevin P
KP
D000818:Animals; D001921:Brain / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D018076:DNA, Complementary; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D011994:Recombinant Proteins