Figure 5.
14-3-3ε modulation has a significant effect on protein synthesis and load in MM cells. (A) Protein synthesis was analyzed by flow cytometry in AMO1 cell line infected with either scrambled (pLKO.1) or 14-3-3ε-targeted shRNA. The overlay histogram plot shows mean fluorescent intensity (MFI) of incorporated l-homopropargylglycine (HPG) (Alexa Fluor 488) into proteins of pLKO.1 (red) and KD (blue) cells during active protein synthesis. In the inset, results are expressed as percentage change compared with pLKO.1 control cell. (B) Protein synthesis was analyzed by flow cytometry in H929 (black) and JJN3 (red) MM cell lines infected with either scrambled (pLKO.1) or 14-3-3ε-targeted shRNAs. Results are expressed as percentage change compared with each pLKO.1 control cell. (C) Protein synthesis was analyzed by flow cytometry in KMS20 MM cells infected with either pLenti6-empty (empty, red) or pLenti6-FLAG-YWHAE OE plasmid (14-3-3ε, blue), expressed as percentage change compared with control cells. (D) Protein synthesis was analyzed by flow cytometry in SKMM1 MM cells infected with either pLenti6-empty (empty) or pLenti6-FLAG-YWHAE OE plasmid (14-3-3ε). The overlay histogram plot shows MFI of incorporated HPG (Alexa Fluor 488) into proteins of empty control (red), 14-3-3ε OE (blue), and 14-3-3ε OE cells treated with rapamycin (5 μM, 24 hours; green) during active protein synthesis. The purple histogram represents the negative control. In the inset, results are expressed as percentage of empty control cells. (E) Flow cytometry evaluation of protein synthesis in H929 KO MM cells infected with either pLenti6-empty (empty) or pLenti6-FLAG-YWHAE OE plasmid (14-3-3ε). The overlay histogram plot shows MFI of incorporated HPG (Alexa Fluor 488) into proteins of empty (red) and addback (blue) cells. In the inset, results are expressed as percentage change compared with control cells. (F-G) Flow cytometry analysis of clonal cytoplasmic κ light chain expression in 14-3-3ε KD (F) or OE (G) MM cell line. Results are expressed as percentage change compared with each control cells. (H-I). Secreted M protein was evaluated by ELISA assay in 14-3-3ε KD (H) or OE (I) MM cell line. Results are expressed as percentage change compared with control cells. Data were analyzed using unpaired Student t tests: *P ≤ .05; **P ≤ .01; ***P ≤ .001; ****P ≤ .0001.