Glycosylation of the Na+/H+ exchanger isoform NHE-3 is species specific

The glycosylation of Na+/H+ exchanger isoform NHE-3 was studied in brush border membrane (BBM) vesicles isolated from rabbit, dog, and rat kidney cortex. Western blot analyses were performed against BBM proteins by using polyclonal antibodies to an NHE-3 fusion protein. In rabbit kidney, NHE-3 antibody recognized a band with approximately 95 kd molecular mass. Treatment of rabbit cortical BBM with glycopeptidase F, at 16 U/ml, for 4 or 16 hours increased the apparent mobility of NHE-3 to 84 and 82 kd, respectively. Incubation of rabbit BBM proteins for 16 hours with endoglycosidase H, at 0.1 U/ml, did not alter the apparent mobility of NHE-3. Deglycosylation of NHE-3 with glycopeptidase F did not affect acid-stimulated, amiloride-sensitive sodium 22 influx in BBM vesicles as compared with that in controls (p > 0.05). Immunoblot analysis against BBM proteins from canine kidney cortex demonstrated the presence of an approximately 83 to 92 kd protein. Treatment of canine BBM with glycopeptidase F or endoglycosidase H or F for 16 hours did not alter the apparent mobility of NHE-3, suggesting that canine renal NHE-3 is not glycosylated. Treatment of canine kidney BBM with glycopeptidase F did not affect acid-stimulated 22Na+ influx as compared with that in controls (p > 0.05). Immunoblot analysis against BBM proteins from rat kidney cortex demonstrated the presence of a sharp band at 90 kd. Treatment of rat BBM with glycopeptidase F or endoglycosidase H or F for 16 hours did not alter the apparent mobility of NHE-3, suggesting that rat renal NHE-3 is not glycosylated. The above experiments suggest that NHE-3 glycosylation in mammalians is species specific and that glycosylation does not affect the exchanger activity.