ABSTRACT
Objective To investigate the effect of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) on autophagy induction by ionizing radiation ( IR ) .Methods The cell model of knocking-down DNA-PKcs expression was constructed by transfecting HeLa cells with a pSicoR-based lentivirus vector expressing DNA-PKcs specific shRNA .Cellular growth activity and radiosensitivity were detected by cell countingkit ( CCK)-8 assay.The expression of autophagy related proteins was detected by Western blotting hybridization .Autophagy was also detected by monitoring the autophagic marker green fluorescere protein ( GFP )-light chain 3 ( LC3 ) puncta per cell under an immunofluorescent microscope .Results A cellular model of knocking-down DNA-PKcs expression was successfully generated by transfecting the specific shRNA against DNA-PKcs.Depression of DNA-PKcs significantly decreased the growth activity of HeLa cells and increased the cellular sensitivity to ionizing radiation .Both the expression changes of P 62 and LC3 proteins and immunofluorescent GFP-LC3 puncta observation indicated that knocking-down DNA-PKcs prompted the induction of autophagy by ionizing radiation . Moreover, inactivation of DNA-PKcs led to a decreased phosphorylation of mammalian target of sirolimus ( Rapamycin, RAPA) ( mTOR) at S2481 site.Conclusion Depression of DNA-PKcs expression prompts the induction of autophagy by IR and cellular radiosensitivity .mTOR signaling may be involved in the regulation of autophagy processing by DNA-PKcs.