Figure 3. MTORC1, but not MTORC2, is involved in the regulation of different PIK3C3 complexes. (A) Amino acid starvation only activates the ATG14-containing PIK3C3 lipid kinase activity. Different PIK3C3 complexes were immunoprecipitated from MEFs that were cultured in nutrient-rich or AA-free medium for 1 h, and subjected to lipid kinase assay and immunoblot. (B) Quantification of (A). (C) RPTOR knockdown activates ATG14-PIK3C3. Different PIK3C3 complexes from scrambled or Rptor KD MEFs were immunoprecipitated with corresponding antibodies and subjected to lipid kinase assay. The right panel indicates RPTOR protein levels in control or Rptor KD MEFs. (D) Rictor knockout has no effect on ATG14-PIK3C3 activity. Different PIK3C3 complexes from RICTOR WT or Rictor KO MEFs were immunoprecipitated with corresponding antibodies and subjected to lipid kinase assay. The right panel indicates RICTOR protein levels in WT or Rictor KO MEFs.