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A protein complex in the brush‐border membrane explains a Hartnup disorder allele
Author(s) -
Kowalczuk Sonja,
Bröer Angelika,
Tietze Nadine,
Vanslambrouck Jessica M.,
Rasko John E. J.,
Bröer Stefan
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.08-107300
Subject(s) - brush border , amino acid , biology , leucine , biochemistry , carboxypeptidase , transporter , peptide , enzyme , chemistry , gene , membrane , vesicle
Protein absorption in the intestine is mediated by proteases and brush‐border peptidases together with peptide and amino acid transporters. Neutral amino acids are generated by a variety of aminopeptidases and carboxypeptidases and are subsequently taken up by the amino acid transporter B 0 AT1 (SLC6A19), which is mutated in Hartnup disorder. Coexpression of B 0 AT1 together with the brush‐border carboxypeptidase angiotensin‐converting enzyme 2 (ACE2) in Xenopus laevis oocytes led to a dramatic increase of transporter expression at the oocyte surface. Other members of the SLC6 family were not stimulated by coexpression with ACE2. Addition of a peptide containing a carboxyterminal leucine residue to ACE2‐ and B 0 AT1‐coexpressing oocytes caused inward currents due to Na + ‐leucine cotransport, demonstrating the formation of a metabolic complex. Coexpression of the Hartnup disorder causing mutation B 0 AT1(R240Q) showed reduced interaction with ACE2 and its renal paralogue collectrin. This would result in reduced surface expression in both kidney and intestine, thereby explaining the onset of the disorder in individuals carrying this mutation.—Kowalczuk, S., Bröer, A., Tietze, N., Vanslambrouck, J. M., Rasko, J. E. J., Bröer, S. A protein complex in the brush‐border membrane explains a Hartnup disorder allele. FASEB J. 22, 2880–2887 (2008)