Differential expression and regulation of AE2 anion exchanger subtypes in rabbit parietal and mucous cells

1. The anion exchanger isoform 2 (AF2)gene encodes three subtypes (AE2a, b and c), which hale different N-termini and tissue distributions. AE2 is exp ressed at high level, in the stomach, where it is thought to mediate basola teral base exit during acid production. The present. study investigated if the three AE2 subtype, are differentially expressed anti regulated in diffe rent cell types within the gastric mucosa. 2. The cloning strategy to obtain rabbit AE2a, b and c cDNAs combined genom ic PCR and RT-PCR biased on primers deduced front the rat sequences. Semiqu antitative RT-PCR using homologous primers revealed much higher AE2 mRNA ex pression in rabbit parietal cell, (PCs) than in mucous cell, (MCs). The sub type expression pattern was AE2b >> AE2c greater than or equal to AE2a in P Cs and AE2a > AE2b >> AE2c in MCs. Sequence analysis revealed the presence of a highly conserved protein kinase C (PKC) consensus sequence in the AE2a alternative N-terminus. 3. Maximal Cl--HCO3- exchange rates, measured fluorometrically in BCECF-loa ded cultured gastric cells, were much higher in PC's than MC,. PKC activati on by phorbol ester stimulated maximal Cl--HCO3- exchange rates in MCs but not. in PCs, whereas forskolin had no effect in each cell type. 4. In summary, rabbit PCs and Ws, which originate from the same gastric,ten s cell population, display a completely different AE2 subtype expression pa ttern. Therefore, AE2 subtype expression is not organ specific but cell typ e specific. The different regulation of anion exchange in parietal and muco us cells suggests that AE2 subtype, may lm differentially regulated.