Characteristics of a human N-type calcium channel expressed in HEK293 cells
The human α 1 B−1 β 1−2 Ca 2+ channel was stably expressed in HEK293 cells producing a human brain N-type voltage-dependent calcium channel (VDCC). Whole cell voltage-clamp electrophysiology and fura-2 based microfluorimetry have been used to study its characteristics. Calcium currents (I Ca) record...
Saved in:
Published in | Neuropharmacology Vol. 34; no. 7; pp. 753 - 765 |
---|---|
Main Authors | , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
01.07.1995
Elsevier |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | The human
α
1
B−1
β
1−2
Ca
2+ channel was stably expressed in HEK293 cells producing a human brain N-type voltage-dependent calcium channel (VDCC). Whole cell voltage-clamp electrophysiology and fura-2 based microfluorimetry have been used to study its characteristics. Calcium currents (I
Ca) recorded in transfected HEK293 cells were activated at potentials more depolarized than — 20 mV with peak currents occuring at approx + 10 mV in 5 mM extracellular CaCl
2. I
Ca and associated rises in intracellular free calcium concentrations ([Ca
2+]
i) were sensitive to changes in both the [Ca
2+]
o and holding potential. Steady-state inactivation was half maximal at a holding potential of — 60 mV. Ba
2+ was a more effective charge carrier than Ca
2+ through the
α
1
B−1
α
2
b
β
1−2
Ca
2+ channel and combinations of both Ba
2+ and Ca
2+ as charge carriers resulted in the anomalous mole fraction effect. Ca
2+ influx into transfected HEK293 cells was irreversibly inhibited by ω-conotoxin-GVIA (ω-CgTx-GVIA; 10 nM-1 μM) and cu-conotoxin-MVIIA (ω-CmTx-MVHA; 100 nM-1 μM) whereas no reductions were seen with agents which block P or L-type Ca
2+ channels. The inorganic ions, gadolinium (Gd
3+), cadmium (Cd
2+) and nickel (Ni
2+) reduced the I
Ca under voltage-clamp conditions in a concentration-dependent manner. The order of potency of the three ions was Gd
3+,Cd
2+,Ni
2+. These experiments suggest that the cloned and expressed
α
1
B−1
α
2
b
β
1−2
Ca
2+ channel subunits form channels in HEK.293 cells that exhibit properties consistent with the activity of the native N-type VDCC previously described in neurons. |
---|---|
Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0028-3908 1873-7064 |
DOI: | 10.1016/0028-3908(95)00078-K |