Differential expression of P-type ATPases in intestinal epithelial cells: identification of putative new atp1a1 splice-variant.

P-type ATPases are membrane proteins that couple ATP hydrolysis with cation transport across the membrane. Ten different subtypes have been described. In mammalia, 15 genes of P-type ATPases from subtypes II-A, II-B and II-C, that transport low-atomic-weight cations (Ca(2+), Na(+), K(+) and H(+)), have been reported. They include reticulum and plasma-membrane Ca(2+)-ATPases, Na(+)/K(+)-ATPase and H(+)/K(+)-ATPases. Enterocytes and colonocytes show functional differences, which seem to be partially due to the differential expression of P-type ATPases. These enzymes have 9 structural motifs, being the phosphorylation (E) and the Mg(2+)ATP-binding (H) motifs the most preserved. These structural characteristics permitted developing a Multiplex-Nested-PCR (MN-PCR) for the simultaneous identification of different P-type ATPases. Thus, using MN-PCR, seven different cDNAs were cloned from enterocytes and colonocytes, including SERCA3, SERCA2, Na(+)/K(+)-ATPase alpha1-isoform, H(+)/K(+)-ATPase alpha2-isoform, PMCA1, PMCA4 and a cDNA-fragment that seems to be a new cassette-type splice-variant of the atp1a1 gen. PMCA4 in enterocytes and H(+)/K(+)-ATPase alpha2-isoform in colonocytes were differentially expressed. This cell-specific expression pattern is related with the distinctive enterocyte and colonocyte functions.