Characterization and Functional Expression of Genomic DNA Encoding the Human Lymphocyte TypenPotassium Channel

摘要

ABSTRACTVoltage-gated potassium channels play important functional roles in the development and maintenance of human lymphocyte functions. One such channel, known as the typenchannel, has been well defined in human T cells and exhibits unique functional properties that distinguish it from other species of potassium channels. We report the characterization of a human genomic DNA clone, HGK5, encoding a 523-amino-acid potassium channel protein encoded by an open reading frame on a single exon. RNA transcribedin vitrofrom HGK5 genomic DNA directs expression of functional voltage-dependent potassium currents inXenopusoocytes. The functional characteristics of the expressed channels are strikingly similar to those of the typenchannel on human T lymphocytes. This, together with the presence of significant levels of HGK5 mRNA in human T lymphocytes, supports the notion that HGK5 encodes the human typenvoltage-gated potassium channel. The effects of concanavalin A treatment on HGK5 mRNA levels in cultured human T lymphocytes was also examined. Mitogenic concentrations of concanavalin A induced a time-dependent decrease in HGK5 mRNA levels, suggesting that previously observed increases in potassium current density following concanavalin A treatment of human T lymphocytes are not due to increased transcriptional activity of the typenpotassium channel gene.