CHIP Ubiquitinatied And Degradatied Nur77 To Alleviate Cisplatin-induced Acute Kidney Injury And Its Machenism Involved

Background: Acute kidney injury(AKI)is a common clinical disease that can lead to various electrolyte disorders.AKI can be induced by various factors including renal ischemia/reperfusion injury,sepsis,and the administration of nephrotoxic drugs.Cisplatin,as a widely used chemotherapy drug,is one of the most common nephrotoxic drugs.Multiple mechanisms,including apoptosis,pyroptosis and ferroptosis,are involved in cisplatin-induced AKI.Carboxy-terminus of heat shock protein70-interacting protein(CHIP),an E3 ligase activity,is involved in various pathological and physiological processes by driving the heavy unfolding or proteasome/lysosome degradation of its target proteins.However,the role of CHIP in the pathogenesis of cisplatin-induced AKI and its mechanism involved are not fully understood.Objective: This study aimed to investigate the regulatory role of CHIP in the pathogenesis of cisplatin-induced AKI and its underlying molecular mechanisms.Methods: BUMPT cells(a mouse proximal tubule cell line)were used for in vitro studies,and C57BL/6J mice were used for in vivo studies.Cisplatin was used to induce AKI in cells or mice.Changes in the expression profile of CHIP in cisplatin-induced AKI were examined by Western blot analysis,q RT-PCT analysis,immunohistochemistry staining,and immunofluorescence staining.Then,the expression of CHIP in vitro was manipulated by lentivirus infection,and the gene expression of CHIP in vivo was manipulated by intraparenchymal injection of adenovirus.Besides YL-109 was also used to induce the expression of CHIP protein in in vivo and in vitro studies.Cell damage was evaluated by cell morphology and cell survival rate.Changes in intracellular reactive oxygen species levels were detected by DHE staining and flow cytometry,and intracellular DNA damage was detected by TUNEL staining.Apoptosis-related markers were detected by immunoblotting.The subcellular localization of Nur77 was detected by co-immunofluorescence staining and western-blot studies.The exact interaction pattern between CHIP and Nur77 was explored by immunoprecipitation,protein truncation,and site-directed mutagenesis.Results: In this study,CHIP was mainly expressed in the renal proximal tubular cells,and its expression was decreased in cisplatininduced acute kidney injury.Cisplatin induced cellular and renal injuries,including the increase of intracellular reactive oxygen species levels and cell apoptosis,were alleviated by CHIP overexpression or YL-109 activation.Within expectation,CHIP knockdown presented the opposite effect.Mechanistically,it was found that CHIP interacts with Nur77 LBD domain via its central coiled-coil(CC)domain,a non-canonical interactive pattern.Further in-depth investigation showed that CHIP drives K48-linked polyubiquitination of Nur77 to induce its proteasomal degradation,thus maintaining mitochondrial permeability in cisplatin-treated proximal tubular cells.Conclusion: CHIP plays a pivoltal role in the pathogensis of cisplatin-induced AKI.CHIP interactes with the LBD domain of Nur77 via its CC domain,leading to the ubiquitination and degradation of Nur77.In this regard,the interaction between Nur77 and Bcl-2 is attenuated,thus decelerating apoptosis in cisplatin-treated proximal tubular cells to alleviate the renal injuries.This study suggests that CHIP may be a potential therapeutic target for cisplatin-induced acute kidney injury.