title: Functional characterization of alternative splicing in the C terminus of L-type CaV1.3 channels.
abstract: Ca(V)1.3 channels are unique among the high voltage-activated Ca(2+) channel family because they activate at the most negative potentials and display very rapid calcium-dependent inactivation. Both properties are of crucial importance in neurons of the suprachiasmatic nucleus and substantia nigra, where the influx of Ca(2+) ions at subthreshold membrane voltages supports pacemaking function. Previously, alternative splicing in the Ca(V)1.3 C terminus gives rise to a long (Ca(V)1.3(42)) and a short form (Ca(V)1.3(42A)), resulting in a pronounced activation at more negative voltages and faster inactivation in the latter. It was further shown that the C-terminal modulator in the Ca(V)1.3(42) isoforms modulates calmodulin binding to the IQ domain. Using splice variant-specific antibodies, we determined that protein localization of both splice variants in different brain regions were similar. Using the transcript-scanning method, we further identified alternative splicing at four loci in the C terminus of Ca(V)1.3 channels. Alternative splicing of exon 41 removes the IQ motif, resulting in a truncated Ca(V)1.3 protein with diminished inactivation. Splicing of exon 43 causes a frameshift and exhibits a robust inactivation of similar intensity to Ca(V)1.3(42A). Alternative splicing of exons 44 and 48 are in-frame, altering interaction of the distal modulator with the IQ domain and tapering inactivation slightly. Thus, alternative splicing in the C terminus of Ca(V)1.3 channels modulates its electrophysiological properties, which could in turn alter neuronal firing properties and functions.
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597; NUS Graduate School for Integrative Engineering and Science, National University of Singapore, Singapore 117597.
authors: Bao Zhen
authors: BZ
authors: Tan
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597.
authors: Fengli
authors: F
authors: Jiang
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597.
authors: Ming Yeong
authors: MY
authors: Tan
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597.
authors: Dejie
authors: D
authors: Yu
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597; NUS Graduate School for Integrative Engineering and Science, National University of Singapore, Singapore 117597.
authors: Hua
authors: H
authors: Huang
authors: National Neuroscience Institute, Singapore 308433.
authors: Yiru
authors: Y
authors: Shen
authors: Department of Physiology, Yong Loo Lin School Medicine, National University of Singapore, Singapore 117597; NUS Graduate School for Integrative Engineering and Science, National University of Singapore, Singapore 117597; National Neuroscience Institute, Singapore 308433. Electronic address: phsstw@nus.edu.sg.
authors: Tuck Wah
authors: TW
authors: Soong
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry*; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D004594:Electrophysiology / Q000379:methods; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000379:methods; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013116:Spinal Cord / Q000378:metabolism
chemical_list: C472073:CACNA1D protein, human; C485995:Cacna1d protein, mouse; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; C093712:Cacna1d protein, rat