Wreden Christopher C, Johnson Juliette, Tran Cindy, Seal Rebecca P, Copenhagen David R, Reimer Richard J, Edwards Robert H
Department of Neurology and Physiology, University of California San Francisco School of Medicine, San Francisco, California 94143-0435, USA.
J Neurosci. 2003 Feb 15;23(4):1265-75. doi: 10.1523/JNEUROSCI.23-04-01265.2003.
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.
近期的研究发现了一种转运中性氨基酸的溶酶体蛋白（LYAAT1）。我们现在表明，LYAAT1介导H⁺共转运，其化学计量比为1个H⁺/1个氨基酸，这与它在从溶酶体中主动排出氨基酸的过程中所起的作用相一致。然而，在神经元中，LYAAT1不仅定位于溶酶体，还定位于轴突。在轴突中，LYAAT1与突触标记物不共定位。相反，轴突中的LYAAT1与外排体共定位，这表明表达LYAAT1的膜在确定胞吐作用位点方面发挥作用。蛋白酶保护试验和细胞内pH值测量进一步表明，LYAAT1在质膜上大量表达，这增加了LYAAT1在细胞表面以及溶酶体中发挥生理作用的可能性。
