Endogenous KV channels in human embryonic kidney (HEK-293) cells

The human embryonic kidney cells (HEK-293) have been widely used as one mammalian expression system in the study of voltage-gated K+ (K-V) channels. Understanding the endogenous K-V channels in these cells is the prerequisite for the characterization of the heterogeneously expressed K-V channels in these cells. In the present study we screened the transcriptional expression of different K-V genes in HEK-293 cells using reverse transcribed DNA polymerase chain reaction (RT-PCR) method. Among 16 K-V genes examined in native HEK-293 cells 10 K-V genes were reproducibly amplified, including those Kv alpha subunits encoding for the delayed rectifier (I-K) [K(V)1.1, K(V)1.2, K(V)1.3, K(V)1.6, and K(V)3.1], and for the transient outward K-V channels (I-A) [K(V)1.4, K(V)3.3, K(V)3.4, and K(V)4.1] as well as a K(V)Beta2 subunit. The whole-cell outward rectifier I-K currents in the native HEK-293 cells were recorded (203 +/- 13 pA at +30 mV, n = 82) with the patch-clamp technique. In about 42% of the examined cells, I-A coexited with I-K currents. I-K currents were inhibited by tetraethylammonium chloride (TEA) at 1 and 10 mM by 39.5 and 48.4%, respectively. A 39.6% inhibition of I-K currents was also observed in the presence of 4-aminopyridine (4-AP, 5 mM). Interestingly, both TEA and 4-AP also inhibited I-A currents. 4-acelamido-4'-isothiocyanalostilbene-2, 2'-disulfonic acid (1 mM), a Cl- channel blocker, had no effect on the endogenous outward currents. We concluded that multiple endogenous K-V genes were expressed in native HEK-293 cells, which possessed significant endogenous I-K and I-A currents with unique pharmacological properties.