Molecular cloning and expression of aquaporin 1 [correction of aquapolin 1] (AQP1) in dog kidney and erythroblasts.

Complementary DNA of the water channel aquaporin 1 (AQP1) was cloned from dog kidney and erythroblasts. The cDNA amplified from mRNA in dog kidney was 816 bp, the same as that in bovines, but longer by 6 bp than that in humans, mice and rats. The 235-bp fragment cDNA amplified from the mRNA in dog erythroblasts, which was differentiated from peripheral blood, was completely identical to the corresponding sequence of cDNA from the dog kidney. Thus, mature red blood cells from dog may have AQP1 in their cell membranes. The amino acid sequence in dog AQP1 was 91-94% identical to that in the other species mentioned above. Dog AQP1 has six predicted transmembrane domains, two NPA motifs, one mercury-sensitive site and four consensus phosphorylation sites, the same as the other species. However, dog and bovine AQP1 have only one N-glycosylation site, while two glycosylation sites were found in human and rodent AQP1. Xenopus oocytes injected with the mRNA of the dog AQP1 exhibited high water permeability in a hyposmotic medium. Thus, dog AQP1 performs water transport the same as in the other species.