Mechanism of Ca(v)1.2 channel modulation by the amino terminus of cardiac beta2-subunits.
L-type calcium channels are composed of a pore, alpha1c (Ca(V)1.2), and accessory beta- and alpha2delta-subunits. The beta-subunit core structure was recently resolved at high resolution, providing important information on many functional aspects of channel modulation. In this study we reveal differential novel effects of five beta2-subunits isoforms expressed in human heart (beta(2a-e)) on the single L-type calcium channel current. These splice variants differ only by amino-terminal length and amino acid composition. Single-channel modulation by beta2-subunit isoforms was investigated in HEK293 cells expressing the recombinant L-type ion conducting pore. All beta2-subunits increased open probability, availability, and peak current with a highly consistent rank order (beta2a approximately = beta2b > beta2e approximately = beta2c > beta2d). We show graded modulation of some transition rates within and between deep-closed and inactivated states. The extent of modulation correlates strongly with the length of amino-terminal domains. Two mutant beta2-subunits that imitate the natural span related to length confirm this conclusion. The data show that the length of amino termini is a relevant physiological mechanism for channel closure and inactivation, and that natural alternative splicing exploits this principle for modulation of the gating properties of calcium channels.
Herzig
Stefan
S
Department of Pharmacology, University of Cologne, Gleueler Strasse 24, 50931 Köln, Germany. stefan.herzig@uni-koeln.de
Khan
Ismail F Y
IF
Gründemann
Dirk
D
Matthes
Jan
J
Ludwig
Andreas
A
Michels
Guido
G
Hoppe
Uta C
UC
Chaudhuri
Dipayan
D
Schwartz
Arnold
A
Yue
David T
DT
Hullin
Roger
R
D000328:Adult; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D015870:Gene Expression; D006801:Humans; D015640:Ion Channel Gating; D008297:Male; D009206:Myocardium / Q000737:chemistry*; D012326:RNA Splicing; D013269:Stochastic Processes
D020746:Calcium Channels, L-Type; D017931:DNA Primers; C419385:L-type calcium channel alpha(1C)