title: The H+-coupled electrogenic lysosomal amino acid transporter LYAAT1 localizes to the axon and plasma membrane of hippocampal neurons.
abstract: Recent work has identified a lysosomal protein that transports neutral amino acids (LYAAT1). We now show that LYAAT1 mediates H+ cotransport with a stoichiometry of 1 H+/1 amino acid, consistent with a role in the active efflux of amino acids from lysosomes. In neurons, however, LYAAT1 localizes to axonal processes as well as lysosomes. In axons LYAAT1 fails to colocalize with synaptic markers. Rather, axonal LYAAT1 colocalizes with the exocyst, suggesting a role for membranes expressing LYAAT1 in specifying sites for exocytosis. A protease protection assay and measurements of intracellular pH further indicate abundant expression at the plasma membrane, raising the possibility of physiological roles for LYAAT1 on the cell surface as well as in lysosomes.
authors.affiliation: Department of Neurology and Physiology, University of California San Francisco School of Medicine, San Francisco, California 94143-0435, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Wreden
authors.forename: Juliette
authors.initials: J
authors.lastname: Johnson
authors.forename: Cindy
authors.initials: C
authors.lastname: Tran
authors.forename: Rebecca P
authors.initials: RP
authors.lastname: Seal
authors.forename: David R
authors.initials: DR
authors.lastname: Copenhagen
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Reimer
authors.forename: Robert H
authors.initials: RH
authors.lastname: Edwards
mesh_terms: D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000032:analysis* / Q000737:chemistry / Q000502:physiology*; D026921:Amino Acid Transport Systems, Neutral / Q000032:analysis* / Q000737:chemistry / Q000502:physiology*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000737:chemistry; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000737:chemistry; D002478:Cells, Cultured; D005089:Exocytosis; D006367:HeLa Cells; D006624:Hippocampus / Q000737:chemistry* / Q000166:cytology; D006801:Humans; D017136:Ion Transport; D008247:Lysosomes / Q000737:chemistry; D008969:Molecular Sequence Data; D009474:Neurons / Q000737:chemistry* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011522:Protons; D051381:Rats; D016415:Sequence Alignment; D027981:Symporters; D014981:Xenopus
chemical_list: D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D011522:Protons; C493537:Slc36a1 protein, rat; D027981:Symporters