title: Smooth muscle-selective alternatively spliced exon generates functional variation in Cav1.2 calcium channels.
abstract: Voltage-gated calcium channels play a major role in many important processes including muscle contraction, neurotransmission, excitation-transcription coupling, and hormone secretion. To date, 10 calcium channel alpha(1)-subunits have been reported, of which four code for L-type calcium channels. In our previous work, we uncovered by transcript-scanning the presence of 19 alternatively spliced exons in the L-type Ca(v)1.2 alpha(1)-subunit. Here, we report the smooth muscle-selective expression of alternatively spliced exon 9(*) in Ca(v)1.2 channels found on arterial smooth muscle. Specific polyclonal antibody against exon 9(*) localized the intense expression of 9(*)-containing Ca(v)1.2 channels on the smooth muscle wall of arteries, but the expression on cardiac muscle was low. Whole-cell patch clamp recordings of the 9(*)-containing Ca(v)1.2 channels in HEK293 cells demonstrated -9 and -11-mV hyperpolarized shift in voltage-dependent activation and current-voltage relationships, respectively. The steady-state inactivation property and sensitivity to blockade by nifedipine of the +/-exon 9(*) splice variants were, however, not significantly different. Such cell-selective expression of an alternatively spliced exon strongly indicates the customization and fine tuning of calcium channel functions through alternative splicing of the pore-forming alpha(1)-subunit. The generation of proteomic variations by alternative splicing of the calcium channel Ca(v)1.2 alpha(1)-subunit can potentially provide a flexible mechanism for muscle or neuronal cells to respond to various physiological signals or to diseases.
authors.affiliation: National Neuroscience Institute, Singapore 308433.
authors.forename: Ping
authors.initials: P
authors.lastname: Liao
authors.forename: Dejie
authors.initials: D
authors.lastname: Yu
authors.forename: Songqing
authors.initials: S
authors.lastname: Lu
authors.forename: Zhenzhi
authors.initials: Z
authors.lastname: Tang
authors.forename: Mui Cheng
authors.initials: MC
authors.lastname: Liang
authors.forename: Shihui
authors.initials: S
authors.lastname: Zeng
authors.forename: Weiming
authors.initials: W
authors.lastname: Lin
authors.forename: Tuck Wah
authors.initials: TW
authors.lastname: Soong
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000906:Antibodies; D015153:Blotting, Western; D020746:Calcium Channels, L-Type / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D004594:Electrophysiology; D005091:Exons; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*
chemical_list: D000906:Antibodies; D020746:Calcium Channels, L-Type