Isoform expression of the voltage-dependent calcium channel α_1E

The α_1E voltage-dependent calcium channel has not been clearly identified with a specific neuronal calcium current. To help identify the role of α_1E, we examined differential expression of α_1E splice variants in mouse brain and cultured cell lines and examined the gene structure of the region encoding the amino terminal. Three splice variants were analyzed by a ribonuclease protection assay, and a fourth variant reported previously in a fetal human α_1E sequence was also detected in mouse brain and a pituitary cell line. Whole brain, telencephalon, and olfactory bulb contained predominantly the splice variant corresponding to α_1E-I although other known variants could be detected. Neuroendocrine cells in vitro (BTC3 insulinoma cells and AtT-20 pituitary cell lines) expressed predominantly one α_1E isoform. The existence of a 5′ exon accounting for the origin of variant 5′ ends reported in different species was suggested by the sequence of the mouse α_1E gene in the region encoding the amino terminal.