Intestinal peptidases form functional complexes with the neutral amino acid transporter BᴼAT1
Date
2012-08-15
Authors
Fairweather, Stephen J.
Bröer, Angelika
O’Mara, Megan L.
Bröer, Stefan
Journal Title
Journal ISSN
Volume Title
Publisher
Portland Press
Abstract
The brush-border membrane of the small intestine and kidney proximal tubule are the major sites for the absorption and re-absorption of nutrients in the body respectively. Transport of amino acids is mediated through the action of numerous secondary active transporters. In the mouse, neutral amino acids are transported by BᴼAT1 [broad neutral (ᴼ) amino acid
transporter 1; SLC6A19 (solute carrier family 6 member 19)] in the intestine and by BᴼAT1 and BᴼAT3 (SLC6A18) in the kidney. Immunoprecipitation and Blue native electrophoresis of intestinal brush-border membrane proteins revealed that BᴼAT1 forms complexes with two peptidases, APN (aminopeptidase N/CD13)and ACE2 (angiotensin-converting enzyme 2). Physiological
characterization of BᴼAT1 expressed together with these peptidases in Xenopus laevis oocytes revealed that APN increased the substrate affinity of the transporter up to 2.5-fold and also increased its surface expression (Vmax). Peptide competition experiments, in silico modelling and site-directed mutagenesis of APN suggest that the catalytic site of the peptidase is involved in the observed changes of BᴼAT1 apparent substrate affinity, possibly by increasing the local substrate concentration. These results provide evidence for the existence of BᴼAT1-containing digestive complexes in the brush-border membrane, interacting differentially with various peptidases, and responding to the dynamic needs of nutrient absorption in the intestine and kidney.
Description
Keywords
aminopeptidase, N, angiotensin, converting, enzyme, ACE2, broad, neutral, amino, acid, transporter, BᴼAT1, brush, border, membrane, nutrient, absorption, protein, complex
Citation
Collections
Source
Biochemical Journal
Type
Journal article
Book Title
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Access Statement
Open Access
License Rights
Creative Commons Attribution Non-Commercial Licence