H+,K+-ATPase

Both pH and potassium levels are regulated within very narrow ranges in mammals. Ion concentrations outside of these levels are life-threatening. The H+,K+-ATPase hydrolyzes ATP to drive exchange of ions along the nephron and the pump functions to conserve potassium and acidify the urine. All H+,K+-ATPases contain an a and b subunit, but in differing combinations. Work in our laboratory and by others has demonstrated that the rabbit kidney actually contains three isoforms: a1 is similar to the well known acid pump in the stomach while the other two are related to the colonic H+,K+-ATPase. The correct mating of HKa and HKb subunits to form functional H+,K+-ATPases in the kidney remains unknown.

We are investigating regulation at the transcriptional and posttranslational levels for the HKa2 subunit (colonic) H+,K+-ATPases in the kidney. We have cloned both cDNAs and the HKa2 gene from rabbit. In addition, we have obtained clones for four different HKb and NaKb subunits. At the present time our efforts are focused on functional expression of H+,K+-ATPase in mammalian tissue culture and on analysis of the regulatory elements controlling transcription of the HKa2 gene. We are using methods that include traditional cloning, polymerase chain reaction, reporter gene studies, stable and transient transfection. We will be moving into nucleotide array technology in the immediate future. The research was supported by the American Heart Association until the current NIH grant received funding. We continue to enjoy a very active collaboration with Dr. Wingo and his laboratory.

Recent Publications

Otto, T. and Cain, B. (2000) Expression of the rabbit HKa2a and HKa2c ATPases in HEK293 cells. The FASEB Journal 14(8): A1526.

Zies, D., Campbell, W., Gumz, M., and Cain, B. (2000) Molecular characterization of the rabbit renal HKa2 gene. The FASEB Journal 14(8): A1568.

Caviston, T., Campbell, W., Wingo, C., Cain, B. (1999) Molecular identification of the renal H+,K+-ATPases. Seminars in Nephrology 19(5): 431-437.

Campbell, W., Weiner, I., Wingo, C., and Cain, B. (1999) H-K-ATPase in the RCCT-28A rabbit cortical collecting duct cell line. American Journal of Physiology 276(2): F237-F245.