Wip1 enhances genotoxic stress-induced autophagy via ULK1 dephosphorylation in Medulloblastoma cells

Background Autophagy is a conserved lysosomal degradation pathway crucial for cellular homeostasis and survival under stress, including genotoxic stress. WIP1 (PPM1D), a phosphatase that modulates the DNA damage response (DDR), is frequently overexpressed in medulloblastoma and may influence autophagy. This study aimed to investigate the role of WIP1 in genotoxic stress-induced autophagy in D283med medulloblastoma cells. Methods and results D283med medulloblastoma cells were treated with etoposide (Eto) to induce genotoxic stress. Autophagy was assessed via LC3-II accumulation, p62 degradation, and LC3 puncta formation using Western blot and immunofluorescence. WIP1 activity was modulated using the selective inhibitor GSK2830371 (GSK). Etoposide increased WIP1 levels and promoted autophagy, which was further enhanced by co-treatment with chloroquine (CQ) or GSK. DDR activation was confirmed by phosphorylation of ATR, Chk1, and gamma H2AX. WIP1 inhibition elevated p-ULK1 (Ser638) levels, suggesting WIP1-dependent dephosphorylation of ULK1. Immunoprecipitation and confocal microscopy confirmed physical interaction between WIP1 and ULK1. Apoptosis was evaluated using Annexin V/7-AAD assay. Co-inhibition of autophagy and WIP1 enhanced etoposide-induced apoptosis, correlating with increased Bax, cleaved caspase-3, and p53 expression. Conclusions WIP1 promotes autophagy under genotoxic stress via ULK1 dephosphorylation, contributing to tumor cell survival. Inhibition of WIP1 disrupts this protective mechanism and sensitizes cells to apoptosis. Targeting the WIP1-autophagy axis may enhance the efficacy of genotoxic chemotherapy in WIP1-overexpressing tumors.