Cystinurie Forschung Barcelona / Palacin

Herr Dr. Merschbrock hat in 2019/2020 über intensive Nachforschungen auch einen Kontakt nach Barcelona hergestellt.

Dies wurde 2005 von  et.al. Palacin, Barcelona in Physiologie 2005, veröffentlicht.
Mehr über Palacin : https://www.irbbarcelona.org/en/profile/manuel-palacin

Hier Veröffentlichungen ab dem Jahr 2005 über:

Ein Auszug, welcher lt. Dr. Merschbrock gezielt auf eine Transportproblem hinweist. Eine Vereinfachung, die ebenfalls Herr dr. Merschbrock, anlässlich im rahmen der Züchterversammlung Oktober 2019 vorgetragen hat. Findet man auf dieser Webseite unter Cystin beim irish Terrier.

Hier ein Auszug aus dem Original Text.

Heterodimeric amino acid transporters play crucial roles in epithelial transport, as well as in cellular nutrition. Among them, the heterodimer of a membrane protein b(0,+)AT/SLC7A9 and its auxiliary subunit rBAT/SLC3A1 is responsible for cystine reabsorption in renal proximal tubules. The mutations in either subunit cause cystinuria, an inherited amino aciduria with impaired renal reabsorption of cystine and dibasic amino acids. However, an unsolved paradox is that rBAT is highly expressed in the S3 segment, the late proximal tubules, whereas b(0,+)AT expression is highest in the S1 segment, the early proximal tubules, so that the presence of an unknown partner of rBAT in the S3 segment has been proposed. In this study, by means of coimmunoprecipitation followed by mass spectrometry, we have found that a membrane protein AGT1/SLC7A13 is the second partner of rBAT. AGT1 is localized in the apical membrane of the S3 segment, where it forms a heterodimer with rBAT. Depletion of rBAT in mice eliminates the expression of AGT1 in the renal apical membrane. We have reconstituted the purified AGT1-rBAT heterodimer into proteoliposomes and showed that AGT1 transports cystine, aspartate, and glutamate. In the apical membrane of the S3 segment, AGT1 is suggested to locate itself in close proximity to sodium-dependent acidic amino acid transporter EAAC1 for efficient functional coupling. EAAC1 is proposed to take up aspartate and glutamate released into luminal fluid by AGT1 due to its countertransport so that preventing the urinary loss of aspartate and glutamate. Taken all together, AGT1 is the long-postulated second cystine transporter in the S3 segment of proximal tubules and a possible candidate to be involved in isolated cystinuria.

KEYWORDS: amino acid transporter; cystine reabsorption; cystinuria; kidney

weitere Informationen

AGT1-heavy chain heterodimer in mouse kidney. (A) Expression of AGT1 in kidney. Western blot was performed on crude membrane fractions from two female and two male mice using the anti-AGT1(M) antibody. Western blots (Left and Right) were performed in the presence (+DTT) or absence (− DTT) of 100 mM DTT, respectively. Filled arrowheads indicate AGT1. Open arrowhead points to heterodimers of AGT1 and its heavy chain (AGT1-hc heterodimer) whereas the open arrow indicates the oligomeric complex. (B) Immunoprecipitation on renal brush-border membrane vesicles (BBMVs) with the anti-AGT1(M) antibody or anti-rBAT antibody. Western blot was performed with the anti-rBAT antibody or anti-AGT1(M) antibody in the presence of 100 mM DTT. The small arrow (Left) and the arrowhead (Right) indicate the bands for rBAT and AGT1, respectively. The large arrow (Right) indicates the AGT1 homodimer. Normal rabbit IgG was used as a control for immunoprecipitation. Asterisks are the bands derived from IgG. (C) Expression of AGT1 and rBAT in the mutant mouse kidney Western blot was performed on renal BBMVs from different genotypes [WT (Slc7a9+/+ and Slc3a1+/+) and D140G (Slc3a1 missense mutation)] of male (M) and female (F) mice in the nonreducing condition. The anti-AGT1(G) and anti-rBAT antibodies detected AGT1-rBAT heterodimer (arrowhead) and its oligomers, including dimers of heterodimeric complexes (arrowhead 2×) and higher oligomeric complexes (arrow).