Endogenous expression of the beta1A sodium channel subunit in HEK-293 cells.
The expression of the sole alpha-subunit of muscle or brain sodium channels in frog oocytes mediates currents with a bimodal inactivation with an abnormal slow mode that is strongly depressed only by co-expression of the beta1-subunit. In contrast, in the expression of the alpha-subunit in the human embryonic kidney cell line, HEK-293, the slow mode is almost absent, suggesting an endogenous expression of the beta1-subunit. We have tested this hypothesis by reverse transcriptase-polymerase chain reaction. We found an abundant expression of mRNA encoding the beta1A splicing of the putative regulatory sodium channel subunit but no mRNA encoding the beta1-subunit in HEK cells. This finding is consistent with the idea that the endogenous beta1A-subunit is sufficient for suppressing the slowly inactivating mode of sodium currents by co-assembly with alpha-subunits, and calls attention to the reliability of effects attributed in HEK cells to alpha-beta1 co-expression.
Moran
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Istituto di Cibernetica e Biofisica, CNR, Via De Marini 6, I-16149, Genoa, Italy. moran@barolo.icb.ge.cnr.it
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D000818:Animals; D002460:Cell Line; D005260:Female; D015870:Gene Expression; D006801:Humans; D008564:Membrane Potentials; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000378:metabolism; D018075:RNA, Complementary / Q000008:administration & dosage; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015222:Sodium Channels / Q000235:genetics* / Q000502:physiology; D014982:Xenopus laevis
D020033:Protein Isoforms; D018075:RNA, Complementary; D015222:Sodium Channels; D012313:RNA