Fig. 3: MTM1 represses the Ragulator–RagGTPase amino acid-sensing arm of mTORC1.
From: Lysosomal phosphoinositide turnover acts upstream of RagGTPase–mTORC1 and controls muscle growth
a, A volcano plot of lysosomal proteomics showing enrichment of Ragulator/LAMTOR–RagGTPase components in MTM1-KOCas9 myotubes. Data from three biologically independent experiments; two-sided Welch’s t-test; P < 0.01. b, An immunoblot analysis of mTOR complex components and RagGTPases in CTRL and MTM1-KOCas9 myotubes after 9 days in 2% HS. Data are shown as mean ± s.d. from three biologically independent experiments; two-sided Mann–Whitney test. c, The LAMTOR–RagA/C enrichment in lysosomal immunoprecipitates from CTRL and MTM1-KOCas9 myotubes under amino acid starvation (HBSS) after 9 days. Inputs are normalized to LAMTOR levels. Three biologically independent experiments. d, A volcano plot comparing lysosomal and total cellular metabolites between CTRL and MTM1-KOCas9 myotubes. Data from six independent Lyso-IP preparations and three total cell extracts; two-sided Welch’s t-test; P < 0.01. e, The validation of RagA knockdown and expression of RagA WT, constitutively active (Q66L) or dominant-negative (R37P, T21N) mutants. Three biologically independent experiments; one-way ANOVA with Dunnett’s test. f, The effects of RagA manipulation on MTM1-KOCas9 myotube differentiation. Data are shown as mean ± s.d.; n = 25 myotubes from three technical replicates; one-way ANOVA with Dunnett’s test. Scale bar, 100 µm. g,h, Lamtor1 knockdown reduces mTORC1 signalling (g) and restores differentiation (h) in MTM1-KOCas9 myotubes (percentage of multinucleated myotubes and myotube area). Data are shown as mean ± s.d.; n = 48 myotubes per condition from three biologically independent experiments; one-way ANOVA with Dunnett’s test. Scale bar, 100 µm. Protein molecular weight in kDa. Illustration in c created in BioRender; Karim, H. https://biorender.com/n6ucxpz (2026).
