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 expressed at high level, in the stomach, where it is thought to mediate basolateral base exit during acid production. The present. study investigated if the three AE2 subtype, are differentially expressed anti regulated in different cell types within the gastric mucosa. 2. The cloning strategy to obtain rabbit AE2a, b and c cDNAs combined genomic PCR and RT-PCR biased on primers deduced front the rat sequences. Semiquantitative RT-PCR using homologous primers revealed much higher AE2 mRNA expression in rabbit parietal cell, (PCs) than in mucous cell, (MCs). The subtype expression pattern was AE2b >> AE2c greater than or equal to AE2a in PCs 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-loaded cultured gastric cells, were much higher in PC's than MC,. PKC activation 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,tens cell population, display a completely different AE2 subtype expression pattern. Therefore, AE2 subtype expression is not organ specific but cell type specific. The different regulation of anion exchange in parietal and mucous cells suggests that AE2 subtype, may lm differentially regulated.