Fig. 7: Interaction of GLMP with MFSD1.
From: MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes
a, Cartoon representation of GLMP in complex with MFSD1. The interaction site of GLMP with MFSD1 is highlighted in stick representation. b, Zoom in on the interaction of MFSD1 to GLMP as viewed from MFSD1. The electrostatic surface of GLMP is shown. Y416 (MFSD1) is in hydrogen-bond (H-bond) distance to R292 (GLMP) and is highlighted as a black dotted line. c, Zoom in on the interaction of GLMP to MFSD1 as viewed from GLMP. The electrostatic potential surface of MFSD1 is highlighted, indicating complementarity to the GLMP surface. Besides the salt bridge between residues Y416 (MFSD1) and R292 (GLMP), residue D256 (GLMP) is at an H-bond distance from the backbone amide of A261 (GLMP), shown as black dotted lines. The loop region spanning residues 253 to 260 was mutated (blue border). The single-point mutants are highlighted in bold. d, Immunofluorescence-staining of endogenous MFSD1 (red) after transfection with hemagglutinin (HA)-tagged GLMP, GLMP mutants and LAMP1 (green) in Glmp-knockout MEFs. The endogenous LAMP1 is shown in blue. The transfected cells are marked with an asterick. The Pearson correlation coefficient for MFSD1/endogenous LAMP1 is shown in the right panel. The means ± s.e.m. for n = 13–20 cells are shown over two independent experiments (two-tailed unpaired t-tests). *P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001. e, Cellular model for the role of MFSD1 in the recycling of amino acids (AA) derived from lysosomal proteolysis. Owing to its broad selectivity and low affinity for dipeptides, MFSD1 provides an alternative recycling route when the lysosomal breakdown of proteins exceeds the capacity of lysosomal amino acid exporters. Fast cleavage of the released dipeptides by cytosolic aminopeptidases drives MFSD1 activity in the export direction and provides amino acids for biosynthetic pathways. The narrow selectivity of MFSD1 for dipeptides (in contrast with PHT1 and PHT2 transporters) prevents competition by single amino acids and protects this load-shedding route from amino acid overload. The source numerical data are available in the source data.
