NAAG (N-acetylaspartylglutamate) is an abundant neuropeptide in the vertebrate nervous system. It is released from synaptic terminals in a calcium-dependent manner and has been shown to act as an agonist at the type II metabotropic glutamate receptor mGluR3. It has been proposed that NAAG may also be released from axons. So far, however, it has remained unclear how NAAG is transported into synaptic or other vesicles before it is secreted. In the present study, we demonstrate that uptake of NAAG and the related peptide NAAG2 (N-acetylaspartylglutamylglutamate) into vesicles depends on the sialic acid transporter sialin (SLC17A5). This was demonstrated using cell lines expressing a cell surface variant of sialin and by functional reconstitution of sialin in liposomes. NAAG uptake into sialin-containing proteoliposomes was detectable in the presence of an active H+-ATPase or valinomycin, indicating that transport is driven by membrane potential rather than H+ gradient. We also show that sialin is most probably the major and possibly only vesicular transporter for NAAG and NAAG2, because ATP-dependent transport of both peptides was not detectable in vesicles isolated from sialin-deficient mice.
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Research Article|
July 26 2013
Vesicular uptake of N-acetylaspartylglutamate is catalysed by sialin (SLC17A5)
Julia Lodder-Gadaczek;
Julia Lodder-Gadaczek
1Institute of Biochemistry and Molecular Biology, University of Bonn, Nussallee 11, D-53115 Bonn, Germany
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Volkmar Gieselmann;
Volkmar Gieselmann
1Institute of Biochemistry and Molecular Biology, University of Bonn, Nussallee 11, D-53115 Bonn, Germany
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Matthias Eckhardt
Matthias Eckhardt
1
1Institute of Biochemistry and Molecular Biology, University of Bonn, Nussallee 11, D-53115 Bonn, Germany
1To whom correspondence should be addressed (email eckhardt@uni-bonn.de).
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Publisher: Portland Press Ltd
Received:
February 27 2013
Revision Received:
May 28 2013
Accepted:
May 31 2013
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2013 Biochemical Society
2013
Biochem J (2013) 454 (1): 31–38.
Article history
Received:
February 27 2013
Revision Received:
May 28 2013
Accepted:
May 31 2013
Citation
Julia Lodder-Gadaczek, Volkmar Gieselmann, Matthias Eckhardt; Vesicular uptake of N-acetylaspartylglutamate is catalysed by sialin (SLC17A5). Biochem J 15 August 2013; 454 (1): 31–38. doi: https://doi.org/10.1042/BJ20130300
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