Fig. 5: Integration of scavenged extracellular protein into the intracellular amino acid pool through hypoxia-induced macropinocytosis.
From: Hypoxia-induced macropinocytosis represents a metabolic route for liver cancer
a, b The workflow of stable isotope exchange and isotope-tracing experiment. a HCC cells were cultured in 13C,15N-DMEM containing U13C-glucose, U13C-glutamine (U13C-Gln), and 13C,15N-amino acids for 8 cell doublings. The unlabeled amino acids were replaced with isotope-labeled amino acids. b Isotope-labeled HCC cells were cultured in 13C,15N-DMEM with unlabeled BSA (12C-BSA). Without macropinocytosis, intracellular amino acids should remain to be isotope-labeled. With macropinocytosis, scavenged 12C-BSA becomes a source of amino acids and therefore decreases the ratio of isotope-labeled amino acids. c The 13C,15N-labeled fraction of amino acids in MHCC97L-EV, -HIF-1α-KO, and -EHD2-KO cells supplemented with 12C-BSA and exposed to 21 and 1% O2. Values were normalized to 21% O2 EV. Results were from 3 independent mass-spectrometry analysis. Error bars indicate mean ± SD. Two-way ANOVA with Bonferroni correction. Ala alanine, Arg arginine, Asn asparagine, Gly glycine, His histidine, Ile isoleukine, Leu leukine, Lys lysine, Orn ornithine, Phe phenylalanine, Pro proline, Ser serine, Thr threonine, Tyr tyrosine. Source data are provided as a Source Data file.
