Universität zu Köln

Bartels, Peter ORCID: 0000-0001-5852-1835, Yu, Dejie, Huang, Hua ORCID: 0000-0002-7421-3696, Hu, Zhenyu, Herzig, Stefan and Soong, Tuck Wah (2018). Alternative Splicing at N Terminus and Domain I Modulates Ca(v)1.2 Inactivation and Surface Expression. Biophys. J., 114 (9). S. 2095 - 2107. CAMBRIDGE: CELL PRESS. ISSN 1542-0086

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Abstract

The Ca(v)1.2 L-type calcium channel is a key conduit for Ca2+ influx to initiate excitation-contraction coupling for contraction of the heart and vasoconstriction of the arteries and for altering membrane excitability in neurons. Its alpha(1c) pore-forming subunit is known to undergo extensive alternative splicing to produce many Ca(v)1.2 isoforms that differ in their electrophysiological and pharmacological properties. Here, we examined the structure-function relationship of human Ca(v)1.2 with respect to the inclusion or exclusion of mutually exclusive exons of the N-terminus exons 1/1 a and IS6 segment exons 8/8a. These exons showed tissue selectivity in their expression patterns: heart variant 1a/8a, one smooth-muscle variant 1/8, and a brain isoform 1/8a. Overall, the 1/8a, when coexpressed with Ca-v beta(2a), displayed a significant and distinct shift in voltage-dependent activation and inactivation and inactivation kinetics as compared to the other three splice variants. Further analysis showed a clear additive effect of the hyperpolarization shift in V-1/2inact of Ca(v)1 .2 channels containing exon 1 in combination with 8a. However, this additive effect was less distinct for V-1/2act. However, the measured effects were beta-subunit-dependent when comparing Ca-v beta(2a) with Ca-v beta 3 coexpression. Notably, calcium-dependent inactivation mediated by local Ca2+-sensing via the N-lobe of calmodulin was significantly enhanced in exon-1-containing Ca(v)1.2 as compared to exon-1 a-containing Ca(v)1.2 channels. At the cellular level, the current densities of the 1/8a or 1/8 variants were significantly larger than the 1a/8a and 1a/8 variants when coexpressed either with Ca-v beta(2a) or Ca-v beta(3) subunit. This finding correlated well with a higher channel surface expression for the exon 1-Ca(v)1.2 isoform that we quantified by protein surface-expression levels or by gating currents. Our data also provided a deeper molecular understanding of the altered biophysical properties of alternatively spliced human Ca(v)1.2 channels by directly comparing unitary single-channel events with macroscopic whole-cell currents.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Bartels, Peter UNSPECIFIED orcid.org/0000-0001-5852-1835 UNSPECIFIED Yu, Dejie UNSPECIFIED UNSPECIFIED UNSPECIFIED Huang, Hua UNSPECIFIED orcid.org/0000-0002-7421-3696 UNSPECIFIED Hu, Zhenyu UNSPECIFIED UNSPECIFIED UNSPECIFIED Herzig, Stefan UNSPECIFIED UNSPECIFIED UNSPECIFIED Soong, Tuck Wah UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-186570
DOI:	10.1016/j.bpj.2018.03.029
Journal or Publication Title:	Biophys. J.
Volume:	114
Number:	9
Page Range:	S. 2095 - 2107
Date:	2018
Publisher:	CELL PRESS
Place of Publication:	CAMBRIDGE
ISSN:	1542-0086
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language GATED CALCIUM-CHANNEL; SMOOTH-MUSCLE-CELLS; CA2+ CHANNEL; MOLECULAR DETERMINANTS; ALPHA(1C) SUBUNIT; AUXILIARY SUBUNITS; BETA-SUBUNITS; EXONS 40-42; CALMODULIN; HEART Multiple languages Biophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18657