title: Alternative splicing generates a novel truncated Cav1.2 channel in neonatal rat heart.
abstract: L-type Cav1.2 Ca(2+) channel undergoes extensive alternative splicing, generating functionally different channels. Alternatively spliced Cav1.2 Ca(2+) channels have been found to be expressed in a tissue-specific manner or under pathological conditions. To provide a more comprehensive understanding of alternative splicing in Cav1.2 channel, we systematically investigated the splicing patterns in the neonatal and adult rat hearts. The neonatal heart expresses a novel 104-bp exon 33L at the IVS3-4 linker that is generated by the use of an alternative acceptor site. Inclusion of exon 33L causes frameshift and C-terminal truncation. Whole-cell electrophysiological recordings of Cav1.233L channels expressed in HEK 293 cells did not detect any current. However, when co-expressed with wild type Cav1.2 channels, Cav1.233L channels reduced the current density and altered the electrophysiological properties of the wild type Cav1.2 channels. Interestingly, the truncated 3.5-domain Cav1.233L channels also yielded a dominant negative effect on Cav1.3 channels, but not on Cav3.2 channels, suggesting that Cavβ subunits is required for Cav1.233L regulation. A biochemical study provided evidence that Cav1.233L channels enhanced protein degradation of wild type channels via the ubiquitin-proteasome system. Although the physiological significance of the Cav1.233L channels in neonatal heart is still unknown, our report demonstrates the ability of this novel truncated channel to modulate the activity of the functional Cav1.2 channels. Moreover, the human Cav1.2 channel also contains exon 33L that is developmentally regulated in heart. Unexpectedly, human exon 33L has a one-nucleotide insertion that allowed in-frame translation of a full Cav1.2 channel. An electrophysiological study showed that human Cav1.233L channel is a functional channel but conducts Ca(2+) ions at a much lower level.
authors.affiliation: From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Duke-NUS Graduate Medical School Singapore, Singapore 169857, ping_liao@nni.com.sg.
authors.forename: Ping
authors.initials: P
authors.lastname: Liao
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and.
authors.forename: Dejie
authors.initials: D
authors.lastname: Yu
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and.
authors.forename: Mui Cheng
authors.initials: MC
authors.lastname: Liang
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and.
authors.forename: Jue Jin
authors.initials: JJ
authors.lastname: Wang
authors.affiliation: From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433.
authors.forename: Chye Yun
authors.initials: CY
authors.lastname: Yu
authors.affiliation: From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433.
authors.forename: Gandi
authors.initials: G
authors.lastname: Ng
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and.
authors.forename: Tan Fong
authors.initials: TF
authors.lastname: Yong
authors.affiliation: National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609.
authors.forename: Jia Lin
authors.initials: JL
authors.lastname: Soon
authors.affiliation: National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609.
authors.forename: Yeow Leng
authors.initials: YL
authors.lastname: Chua
authors.affiliation: From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and tuck_wah_soong@nuhs.edu.sg.
authors.forename: Tuck Wah
authors.initials: TW
authors.lastname: Soong
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000235:genetics*; D004247:DNA; D017931:DNA Primers; D005091:Exons; D008297:Male; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D020746:Calcium Channels, L-Type; D017931:DNA Primers; C419385:L-type calcium channel alpha(1C); D004247:DNA
keywords: Alternative Splicing; Calcium Channel; Cardiac Development; Electrophysiology; Ion Channel