HERG1 currents in native K562 leukemic cells.
The human ether-a-go-go related gene (HERG1) K+ channel is expressed in neoplastic cells, in which it was proposed to play a role in proliferation, differentiation and/or apoptosis. K562 cells (a chronic myeloid leukemic human cell line) express both the full-length (herg1a) and the N-terminally truncated (herg1b) isoforms of the gene, and this was confirmed with Western blots and coimmunoprecipitation experiments. Whole-cell currents were studied with a tail protocol. Seventy-eight percent of cells showed a HERG1-like current: repolarization to voltages negative to -40 mV produced a transient peak inward tail current, characteristic of HERG1 channels. Cells were exposed to a HERG-specific channel blocker, E4031. Half-maximal inhibitory concentration (IC50) of the blocker was 4.69 nM: The kinetics of the HERG1 current in K562 cells resembled the rapid component of the native cardiac delayed rectifier current, known to be conducted by heterotetrameric HERG1 channels. Fast and slow deactivation time constants at -120 mV were 27.5 and 239.5 ms, respectively. Our results in K562 cells suggest the assembling of heterotetrameric channels, with some parameters being dominated by one of the isoforms and other parameters being intermediate. Hydrogen peroxide was shown to increase HERG1a K+ current in heterologous expression systems, which constitutes an apoptotic signal. However, we found that K562 HERG1 whole-cell currents were not activated by H2O2.
Cavarra
María S
MS
Laboratorio de Neurofisiología, Instituto de Investigaciones Médicas Alfredo Lanari, Universidad de Buenos Aires-CONICET, C. de Malvinas 3150, Buenos Aires, 1427, Argentina.
del Mónaco
Silvana M
SM
Assef
Yanina A
YA
Ibarra
Cristina
C
Kotsias
Basilio A
BA
D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D051638:Ether-A-Go-Go Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020014:K562 Cells; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology
D017931:DNA Primers; D051638:Ether-A-Go-Go Potassium Channels; C496884:KCNH1 protein, human; D010880:Piperidines; D020033:Protein Isoforms; D011725:Pyridines; C063968:E 4031; D006861:Hydrogen Peroxide