Genetic perturbation of MAPK11 (p38β) promotes radiosensitivity by enhancing IR-associated senescence.

Background and purposeMAPKs are among the most relevant signalling pathways involved in coordinating cell responses to different stimuli. This group includes p38MAPKs, constituted by 4 different proteins with a high sequence homology: MAPK14 (p38), MAPK11 (p38{beta}), MAPK12 (p38{gamma}) and MAPK13 (p38{delta}). Despite their high similarity, each member shows unique expression patterns and even exclusive functions. Thus, analysing protein-specific functions of MAPK members is necessary to unequivocally uncover the roles of this signalling pathway. Here, we investigate the possible role of MAPK11 in the cell response to ionizing radiation (IR). Materials and methodsWe developed MAPK11/14 knockdown through shRNA and CRISPR interference gene perturbation approaches, and analysed the downstream effects on cell responses to ionizing radiation in A549, HCT-116 and MCF-7 cancer cell lines. Specifically, we assessed IR toxicity by clonogenic assays; DNA damage response activity by immunocytochemistry; apoptosis and cell cycle by flow cytometry (Annexin V and propidium iodide, respectively); DNA repair by comet assay; and senescence induction by both X-Gal staining and gene expression of senescence-associated genes by RT-qPCR. ResultsOur findings demonstrate a critical role of MAPK11 in the cellular response to IR by controlling the associated senescent phenotype, and without observable effects on DDR, apoptosis, cell cycle or DNA damage repair. ConclusionOur results highlight MAPK11 as a novel mediator of the cellular response to ionising radiation through the control exerted onto IR-associated senescence. HighlightsO_LIGenetic perturbation of MAPK11, but not MAPK14, promotes radiosensitivity in a panel of tumor cell lines. C_LIO_LIAbrogation of MAPK11 did not modify DNA damage response, proliferation, apoptosis or cell cycle in response to ionizing radiation C_LIO_LIMAPK11 controls ionizing radiation-induced senescence C_LIO_LIMAPK11 expression could be a novel target and biomarker for radiosensitivity C_LI