Tissue-Specific N-Terminal Isoforms from Overlapping Alternate Promoters of the Human AE2 Anion Exchanger Gene

Shared apical sorting of anion exchanger isoforms AE2a, AE2b1, and AE2b2 in primary hepatocytes

“…Thus, the first 17 amino acid triplets of AE2a are replaced by 3 triplets for residues MTQ in AE2b 1 and by 8 triplets for residues MDFLLRPQ in AE2b 2 . In addition to the mRNA level [9][10][11], liver expression of the human AE2 gene has been substantiated at the protein level by using a monoclonal antibody against an AE2 peptide common to all three AE2 isoforms [12]. This study showed AE2 immunoreactivity restricted to the lumenal surface of the hepatobiliary tree [12].…”

“…Although AE genes locate in different chromosomes they all have a similar structure. A frequent feature for AE genes is the usage of alternate promoters that leads to the expression of transcript variants, often in a tissue-and cell-specific manner [1,[7][8][9]. With respect to AE2, three transcript variants have been reported in humans: the full-length message AE2a and the alternative isoforms AE2b 1 and AE2b 2 [9].…”

“…A frequent feature for AE genes is the usage of alternate promoters that leads to the expression of transcript variants, often in a tissue-and cell-specific manner [1,[7][8][9]. With respect to AE2, three transcript variants have been reported in humans: the full-length message AE2a and the alternative isoforms AE2b 1 and AE2b 2 [9]. AE2a mRNA is transcribed from the upstream promoter in most human tissues (liver, stomach, thyroid, prostate, and kidney), while the two alternative isoforms are expressed in a more tissue-restricted fashion (mainly in liver and kidney), from AE2b 2 /AE2b 1 overlapping promoter sequences within intron 2 of the AE2 gene [9].…”

“…With respect to AE2, three transcript variants have been reported in humans: the full-length message AE2a and the alternative isoforms AE2b 1 and AE2b 2 [9]. AE2a mRNA is transcribed from the upstream promoter in most human tissues (liver, stomach, thyroid, prostate, and kidney), while the two alternative isoforms are expressed in a more tissue-restricted fashion (mainly in liver and kidney), from AE2b 2 /AE2b 1 overlapping promoter sequences within intron 2 of the AE2 gene [9]. Alternative transcriptions result in different first exons leading to short 5 0 -diversities in the respective open reading frames [9].…”

“…AE2a mRNA is transcribed from the upstream promoter in most human tissues (liver, stomach, thyroid, prostate, and kidney), while the two alternative isoforms are expressed in a more tissue-restricted fashion (mainly in liver and kidney), from AE2b 2 /AE2b 1 overlapping promoter sequences within intron 2 of the AE2 gene [9]. Alternative transcriptions result in different first exons leading to short 5 0 -diversities in the respective open reading frames [9]. Thus, the first 17 amino acid triplets of AE2a are replaced by 3 triplets for residues MTQ in AE2b 1 and by 8 triplets for residues MDFLLRPQ in AE2b 2 .…”