ISOFORM EXPRESSION OF THE VOLTAGE-DEPENDENT CALCIUM-CHANNEL ALPHA(1E)

The alpha(1E) voltage-dependent calcium channel has not been clearly i dentified with a specific neuronal calcium current, To help identify t he role of alpha(1E), we examined differential expression of alpha(1E) splice variants in mouse brain and cultured cell lines and examined t he gene structure of the region encoding the amino terminal. Three spl ice variants were analyzed by a ribonuclease protection assay, and a f ourth variant reported previously in a fetal human alpha(1E) sequence was also detected in mouse brain and a pituitary cell line. Whole brai n, telencephalon, and olfactory bulb contained predominantly the splic e variant corresponding to alpha(1E-1) although other known variants c ould be detected. Neuroendocrine cells in vitro (BTC3 insulinoma cells and AtT-20 pituitary cell lines) expressed predominantly one alpha(1E ) isoform. The existence of a 5' exon accounting for the origin of var iant 5' ends reported in different species was suggested by the sequen ce of the mouse alpha(1E) gene in the region encoding the amino termin al.