AJP - Renal Physiology, Vol 267, Issue 1 70-F74, Copyright © 1994 by American Physiological Society
Functional expression of human renal Na+/Ca2+ exchanger in insect cells
T. W. Loo and D. M. Clarke
Department of Medicine, and Biochemistry, University of Toronto, Ontario, Canada.
The cDNA coding for the human renal isoform of the Na+/Ca2+ exchanger was
cloned from a human embryonic kidney cell line (HEK 293) using a polymerase
chain reaction strategy. It was found by sequence analysis that the cDNA
encoded for a human kidney isoform of the Na+/Ca2+ exchanger. The kidney
isoform is nearly identical to the human cardiac Na+/Ca2+ exchanger except
for a segment of amino acids within the predicted cytoplasmic loop region
of the molecule. Within this region, the kidney isoform contains a deletion
of 36 amino acids, as well as a segment of 33 amino acids that is only 33%
identical to the equivalent region of the cardiac exchanger. The cDNA was
then tested for function by expression in insect cells. We constructed a
recombinant baculovirus containing renal Na+/Ca2+ exchanger cDNA under
control of the polyhedrin promoter. High levels of expression and Na+/Ca2+
exchange activity were found in Sf9 insect cells infected with the
recombinant virus. Our results indicate that human kidney expresses a
functional and alternatively spliced variant of the human cardiac Na+/Ca2+
exchanger.
