1. Differential neuronal targeting of a new and two known calcium channel β4 subunit splice variants correlates with their regulation of gene expression.
- Author
-
Etemad S, Obermair GJ, Bindreither D, Benedetti A, Stanika R, Di Biase V, Burtscher V, Koschak A, Kofler R, Geley S, Wille A, Lusser A, Flockerzi V, and Flucher BE
- Subjects
- Amino Acid Sequence, Animals, Blotting, Western, Calcium Channels metabolism, Female, Hippocampus metabolism, Immunohistochemistry, Male, Mice, Mice, Inbred BALB C, Mice, Knockout, Molecular Sequence Data, Oligonucleotide Array Sequence Analysis, Patch-Clamp Techniques, Protein Isoforms genetics, Protein Isoforms metabolism, Protein Subunits genetics, Protein Subunits metabolism, Reverse Transcriptase Polymerase Chain Reaction, Calcium Channels genetics, Gene Expression genetics, Neurons metabolism
- Abstract
The β subunits of voltage-gated calcium channels regulate surface expression and gating of CaV1 and CaV2 α1 subunits and thus contribute to neuronal excitability, neurotransmitter release, and calcium-induced gene regulation. In addition, certain β subunits are targeted into the nucleus, where they interact directly with the epigenetic machinery. Whereas their involvement in this multitude of functions is reflected by a great molecular heterogeneity of β isoforms derived from four genes and abundant alternative splicing, little is known about the roles of individual β variants in specific neuronal functions. In the present study, an alternatively spliced β4 subunit lacking the variable N terminus (β4e) is identified. It is highly expressed in mouse cerebellum and cultured cerebellar granule cells (CGCs) and modulates P/Q-type calcium currents in tsA201 cells and CaV2.1 surface expression in neurons. Compared with the other two known full-length β4 variants (β4a and β4b), β4e is most abundantly expressed in the distal axon, but lacks nuclear-targeting properties. To determine the importance of nuclear targeting of β4 subunits for transcriptional regulation, we performed whole-genome expression profiling of CGCs from lethargic (β4-null) mice individually reconstituted with β4a, β4b, and β4e. Notably, the number of genes regulated by each β4 splice variant correlated with the rank order of their nuclear-targeting properties (β4b > β4a > β4e). Together, these findings support isoform-specific functions of β4 splice variants in neurons, with β4b playing a dual role in channel modulation and gene regulation, whereas the newly detected β4e variant serves exclusively in calcium-channel-dependent functions.
- Published
- 2014
- Full Text
- View/download PDF