Human Rhesus B and Rhesus C glycoproteins: properties of facilitated ammonium transport in recombinant kidney cells.

The mammalian Rh (Rhesus) protein family belongs to the Amt/Mep (ammonia transporter/methylammonium permease)/Rh superfamily of ammonium transporters. Whereas RhCE, RhD and RhAG are erythroid specific, RhBG and RhCG are expressed in key organs associated with ammonium transport and metabolism. We have investigated the ammonium transport function of human RhBG and RhCG by comparing intracellular pH variation in wild-type and transfected HEK-293 (human embryonic kidney) cells and MDCK (Madin-Darby canine kidney) cells in the presence of ammonium (NH4+/NH3) gradients.

Cell-surface expression of RhD blood group polypeptide is posttranscriptionally regulated by the RhAG glycoprotein.

In most cases, the lack of Rh in Rh(null) red cells is associated with RHAG gene mutations. We explored the role of RhAG in the surface expression of Rh. Nonerythroid HEK293 cells, which lack Rh and RhAG, or erythroid K562 cells, which endogenously express RhAG but not Rh, were transfected with RhD and/or RhAG cDNAs using cytomegalovirus (CMV) promoter-based expression vectors.