Byakangelicin alleviates metabolic dysfunction-associated steatohepatitis by selective inhibition of a non-canonical MTORC1 signaling pathway.

Metabolic dysfunction-associated steatohepatitis (MASH) is emerging as a leading cause of chronic liver disease. MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) is a potential therapeutic target, whereas suppression of total MTORC1 activity can lead to unwanted effects. Here, we found that byakangelicin (Bya), a natural compound, selectively inhibited MTORC1-mediated phosphorylation of TFEB (transcription factor EB), without affecting canonical MTORC1 substrates. Knockout of hepatic Tfeb blocked the alleviation effects of Bya on hepatic steatosis, inflammation, insulin resistance, and fibrosis in mice, while reintroduction of TFEB restored these effects. We identified Bya directly bound to MET370 and PHE552 of FLCN (folliculin), suppressing the function of the FLCN-FNIP1 (folliculin interacting protein 1)/FNIP2 complex, which in turn inhibited MTORC1-mediated cytoplasmic sequestration of TFEB. Mutation of FLCN (M370A and F552A) in the liver abolished Bya-induced protection against MASH. Thus, Bya is a promising therapeutic natural compound for MASH, and selective inhibition of MTORC1 is a potential approach to treat this disease.Abbreviations: aa, amino acids; AAV, adeno-associated virus; Bio, biotin; Bio-Bya, biotin-conjugated Bya; BSA, bovine serum albumin; BW, body weight; Bya, byakangelicin; CETSA, cellular thermal shift assay; CHIP-atlas, chromatin immunoprecipitation atlas; Cmax, maximum concentration; CQ, chloroquine; DARTS; drug affinity responsive target stability assay; EIF4EBP1/4E-BP1, eukaryotic translation initiation factor 4E binding protein 1; FBS, fetal bovine serum; FDA, food and drug administration; FIMO-JASPAR, find individual motif occurrences-JASPAR; FLCN, folliculin; FNIP1, folliculin interacting protein 1; GAP, GTPase-activating protein; GOT1/AST, glutamic-oxaloacetic transaminase 1; GPT/ALT, glutamic-pyruvic transaminase; GTRD, gene transcription regulatory database; GTT, glucose tolerance test; H&E, hematoxylin and eosin; Hbonds, hydrogen bonds; HFD, high-fat diet; HFHC, high-fat and high-cholesterol; HOMA-IR, homeostatic model assessment of insulin resistance; HSCs, hepatic stellate cells; IP, immunoprecipitation; ITT, insulin tolerance test; KD, dissociation constant; KEGG, kyoto encyclopedia of genes and genomes; KPBS, potassium phosphate-buffered saline; LC-MS/MS, liquid chromatography-tandem mass spectrometry; LW/BW, liver-to-body weight ratio; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MASH, metabolic dysfunction-associated steatohepatitis; MASLD, metabolic dysfunction-associated steatotic liver disease; MCD, methionine and choline deficient; MST, microscale thermophoresis assay; MTOR, mechanistic target of rapamycin kinase; MTORC1, MTOR complex 1; ND, normal diet; NFKB/NF-κB, nuclear factor kappa B; NFKBIA/IKBA, NFKB inhibitor alpha; OP, oleate acid and palmitate acid; PBS, phosphate-buffered saline; PCA, principal component analysis; qRT-PCR, real-time quantitative PCR; RELA/p65, RELA proto-oncogene, NF-kB subunit; Res, resmetirom; Rg, radius of gyration; RMSD, root-mean-square deviation; RMSF, root-mean-square fluctuation; RPS3, ribosomal protein S3; RPS6KB1/S6K1, ribosomal protein S6 kinase B1; RRAGC, ras related GTP binding C; SASA, solvent-accessible surface area; SNRPD2, small nuclear ribonucleoprotein D2 polypeptide; SQSTM1/p62, sequestosome 1; T1/2, half-life; TFE3, transcription factor binding to IGHM enhancer 3; TFEB, transcription factor EB; TMEM192, transmembrane protein 192; VIM, vimentin; WT, wild-type.