Cloning and expression of a novel truncated calcium channel from non-excitable cells.

Calcium entry, via a dihydropyridine-sensitive pathway, is required for differentiation in murine erythroleukemia cells (MELC). Calcium channel currents have been identified physiologically in some non-excitable cells, but little is known regarding the structure of these channels. We show that a truncated form of the alpha 1 subunit of the cardiac voltage-gated calcium channel (dihydropyridine receptor, DHPR) is expressed in MELC. This MELC calcium channel lacks the first four transmembrane segments of the DHPR (IS1 to IS4). A MELC calcium channel/cardiac DHPR chimera, co-expressed with the alpha 2 and beta subunits of the DHPR, forms a functional calcium channel in Xenopus oocytes.