High-voltage-activated calcium channel messenger RNA expression in the 140-3 neuroblastoma-glioma cell line

Expression of calcium channel α₁ subunits in oocytes or cell lines has proven to be a powerful method in the analysis of structure-function relations, but these experimental systems are of limited value in the examination of neuron-specific functions such as transmitter release. Cell lines derived from neurons are often capable of these functions, but their intrinsic calcium channel α₁ subunits are complicating factors in experimental design. We have examined the biophysical and molecular properties of calcium channels in a little studied neuroblastoma-glioma hybrid cell line, 140-3, a close relative of the NG108-15 cell line, to test whether this cell line might serve a role as an expression system for neural mechanisms. This cell was selected as it contains an intact transmitter release mechanism yet secretes little in response to depolarization. Patch- clamp recording revealed only a prominent low-threshold, rapidly inactivating calcium current with a single-channel conductance of ~7 pS that was identified as T type. A search for calcium channel α₁ subunit messenger RNA in the 140-3 cells with three different tests only revealed α(1C), whereas α(1A)-α(1C) were present in the parent NG108-15 line. We made a particular effort to search for α(1E), since this subunit has been associated with a low-voltage-activated current. Our findings suggest that, since the principal nerve terminal-associated calcium channels (α(1A), α(1B), α(1E)) are absent in the 140-3 cell, this cell line may prove a particularly useful model for the analysis of the role of high-voltage-activated calcium channels in complex functions of neuronal cells.