The Journal of Neurophysiology Vol. 84 No. 6 December 2000, pp. 2933-2944
Copyright ©2000 by the American Physiological Society

Functional Expression of L-, N-, P/Q-, and R-Type Calcium Channels in the Human NT2-N Cell Line

 ¹Neuroscience Program,  ²Department of Neurology, and  ³Department of Physiology, University of Michigan, Ann Arbor, Michigan 48104-1687

Neelands, Torben R., Anthony P. J. King, and Robert L. Macdonald. Functional Expression of L-, N-, P/Q-, and R-Type Calcium Channels in the Human NT2-N Cell Line. J. Neurophysiol. 84: 2933-2944, 2000. The biophysical and pharmacological properties of voltage-gated calcium channel currents in the human teratocarcinoma cell line NT2-N were studied using the whole cell patch-clamp technique. When held at 80 mV, barium currents (I_Bas) were evoked by voltage commands to above 35 mV that peaked at +5 mV. When holding potentials were reduced to 20 mV or 5 mM barium was substituted for 5 mM calcium, there was a reduction in peak currents and a right shift in the current-voltage curve. A steady-state inactivation curve for I_Ba was fit with a Boltzmann curve (V_1/2 = 43.3 mV; slope = 17.7 mV). Maximal current amplitude increased from 1-wk (232 pA) to 9-wk (1025 pA) postdifferentiation. Whole cell I_Bas were partially blocked by specific channel blockers to a similar extent in 1- to 3-wk and 7- to 9-wk postdifferentiation NT2-N cells: 10 µM nifedipine (19 vs. 25%), 10 µM conotoxin GVIA (27 vs. 25%), 10 µM conotoxin MVIIC (15 vs. 16%), and 1.75 µM SNX-482 (31 vs. 33%). Currents were completely blocked by 300 µM cadmium. In the presence of nifedipine, GVIA, and MVIIC, ~35% of current remained, which was reduced further by SNX-482 (7-14% of current remained), consistent with functional expression of L-, N-, and P/Q-calcium channel types and one or more R-type channel. The presence of multiple calcium currents in this human neuronal-type cell line provides a potentially useful model for study of the regulation, expression and cellular function of human derived calcium channel currents; in particular the R-type current(s).