Functional expression of L-, N-, P/Q-, and R-type calcium channels in the human NT2-N cell line.
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(Ba)s) 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(Ba)s 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 microM nifedipine (19 vs. 25%), 10 microM conotoxin GVIA (27 vs. 25%), 10 microM conotoxin MVIIC (15 vs. 16%), and 1.75 microM SNX-482 (31 vs. 33%). Currents were completely blocked by 300 microM cadmium. In the presence of nifedipine, GVIA, and MVIIC, approximately 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).
Neelands
T R
TR
Neuroscience Program, University of Michigan, Ann Arbor, Michigan 48104-1687, USA.
King
A P
AP
Macdonald
R L
RL
D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000096:biosynthesis*; D020746:Calcium Channels, L-Type / Q000096:biosynthesis; D020864:Calcium Channels, N-Type / Q000096:biosynthesis; D020865:Calcium Channels, P-Type / Q000096:biosynthesis; D020907:Calcium Channels, Q-Type / Q000096:biosynthesis; D020908:Calcium Channels, R-Type / Q000096:biosynthesis; D002454:Cell Differentiation; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D013111:Spider Venoms / Q000494:pharmacology; D018243:Teratocarcinoma / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured; D020866:omega-Conotoxin GVIA / Q000494:pharmacology; D020960:omega-Conotoxins / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D020908:Calcium Channels, R-Type; C115521:SNX 482; D013111:Spider Venoms; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D020866:omega-Conotoxin GVIA; D009543:Nifedipine