Lys05 - A Promising Autophagy Inhibitor in the Radiosensitization Battle: Phosphoproteomic Perspective.

Background: Autophagy is a crucial factor contributing to radioresistance during radiotherapy. Although Lys05 has proven its ability to improve the results of radiotherapy through the inhibition of autophagy, molecular mechanisms of this inhibition remain elusive. We aimed to describe the molecular mechanisms involved in Lys05-induced inhibition of autophagy. Materials and Methods: Radioresistant human non-small cell lung carcinoma cells (H1299, p53-negative) and methods of quantitative phosphoproteomics were employed to define the molecular mechanisms involved in Lys05-induced inhibition of autophagy. Results: We confirmed that at an early stage after irradiation, autophagy was induced, whereas at a later stage after irradiation, it was inhibited. The early-stage induction of autophagy was characterized mainly by the activation of biosynthetic and metabolic processes through up- or down-regulation of the critical autophagic regulatory proteins Sequestosome-1 (SQSTM1) and proline-rich AKT1 substrate 1 (AKTIS1). The late-stage inhibition of autophagy was attributed mainly to down-regulation of Unc-5 I like autophagy-activating kinase 1 (ULK1) through phosphorylation at Ser638. Conclusion: This work contributes to emerging phosphoproteomic insights into autophagy-mediated global signaling in lung cancer cells, which might consequently facilitate the development of precision medicine therapeutics.