Several structural domains contribute to the regulation of N-type calcium channel inactivation by the beta 3 subunit.
Calcium channel beta subunits are essential regulatory elements of the gating properties of high voltage-activated calcium channels. Co-expression with beta(3) subunits typically accelerates inactivation, whereas co-expression with beta(4) subunits results in a slowly inactivating phenotype. Here, we have examined the molecular basis of the differential effect of these two subunits on the inactivation characteristics of Ca(v)2.2 + alpha(2)-delta(1) N-type calcium channels by creating a series of 22 chimeric beta subunits that are based on various combinations of variable and conserved regions of the parent beta subunit isoforms. Our data show that replacement of the N terminus region of beta(4) with a corresponding 14-amino acid stretch of beta(3) sequence accelerates the inactivation kinetics to levels seen with wild type beta(3). A similar kinetic speeding is observed by a concomitant substitution of the second conserved and variable regions, but not when these regions are substituted individually, suggesting that 1) the second variable and conserved regions cooperatively regulate N-type calcium channel inactivation and 2) that there are two redundant mechanisms that allow the beta(3) subunit to accelerate N-type channel inactivation. In contrast with previous reports in Ca(v)2.1 calcium channels, deletion of the C-terminal region of Ca(v)2.2 did not alter the regulation of the channel by wild type and chimeric beta subunits. Hence, the molecular underpinnings of beta subunit regulation of voltage-gated calcium channels appear to vary with calcium channel subtype.
Stotz
Stephanie C
SC
Department of Physiology and Biophysics. Cellular and Molecular Neurobiology Research Group, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Barr
Wendy
W
McRory
John E
JE
Chen
Lina
L
Jarvis
Scott E
SE
Zamponi
Gerald W
GW
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry; D020864:Calcium Channels, N-Type / Q000737:chemistry* / Q000502:physiology*; D002460:Cell Line; D004594:Electrophysiology; D017353:Gene Deletion; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010641:Phenotype; D011233:Precipitin Tests; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D002118:Calcium