Fig. 5: MFSD1 has a broad dipeptide selectivity.
From: MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes
a, Heavy isotope tracer approach used to monitor Leu–Ala transport. b, Representative LC–MS chromatograms of ≥5 independent experiments. The amount of standard (green lines) was 3.9 pmol for Leu(d3)–Ala and 15.6 pmol for Leu(d3) and Ala. c, Relative quantification of the chromatographic peak area of Leu(d3)–Ala, Leu(d3) and Ala in extracts from mock and MFSD1–GLMP oocytes, incubated or not, with, 10 mM Leu(d3)–Ala for 20 min at pH 5.0. The data are means ± s.e.m. of four oocytes from a representative example of three independent experiments (two-tailed unpaired t-tests). *P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001. d, Absolute quantification of Leu–Ala uptake. The data are means ± s.e.m. of 17 oocytes from two oocyte batches. In one experiment, some oocytes were treated with the branched-chained amino acid transaminase inhibitor BAY-069. The Lys–Ala currents from Fig. 2c were divided by the Faraday constant and plotted with the same scale (grey bar) to allow comparison with Leu–Ala uptake. e, A model accounting for the LC–MS/MS data. f, Representative LC–MS chromatograms of eight MFSD1–GLMP oocytes from two batches incubated for 23 min at pH 5.0 with 10 mM Glu–Ala. g, Quantification of Ala in oocytes incubated for 23 min with the indicated dipeptides (10 mM). The means ± s.e.m. of three to four oocytes are depticted. The red dotted line at mid-height of the Ala–Ala bar is shown for comparison with other substrates. Two-tailed unpaired t-tests relative to MFSD1–GLMP oocytes incubated in dipeptide-free buffer; *P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001. The source numerical data are available in the source data.
