Regulatory Effect Of E3 Ubiquitin Ligase NEDD4L On Anti-tumor Immune Response And Its Mechanism

The confrontation,stalemate and compromise between the immune system and tumor cells are the important premise of tumorigenesis,development and fate.Tumor immunotherapy has been a breakthrough and progress in recent years.it has become another pillar of cancer treatment and is improving the survival and prognosis of more tumor patients.Further improving the tumor immune regulation mechanism in the body and exploring specific and widely applicable tumor immunotherapy targets will provide a favorable weapon for researchers and clinicians to conquer cancer as a "health killer".Ubiquitin modified(Ubiquitination)is an important system to regulate the fate of the target protein by affecting its activity,stability or localization.The regulation of ubiquitin modification on the fate of substrate proteins is involved in many cell progresses,such as cell cycle,apoptosis,transcription regulation,DNA repair,immune response,protein degradation and quality control.E3 ubiquitin ligase selectively recruits specific protein substrates through specific protein-protein interaction to determine the specificity of the whole ubiquitin modification reaction.NEDD4L/NEDD4-2(neural precursor cell expressed developmentally down-regulated 4-like)is a member of E3 ubiquitin ligase NEDD4 family and belongs to HECT class E3 s.The mammalian NEDD4 family has nine members: NEDD4(also known as NEDD4-1),NEDD4L(NEDD4-2),ITCH,WWP1,WWP2,NEDL1(HECW1),NEDL2(HECW2),Smurf1 and Smurf2.All of these proteins have similar domains: N-terminal C2 domain,2-4 WW domains,and C-terminal HECT domain.C2 domain is considered to be involved in the membrane localization and transport of these ligases and their substrates.WW domain is considered to be the main medium for their interaction with substrates and ligands,and HECT domain is responsible for the ubiquitin ligase catalytic activity.At present,NEDD4 L has been reported to be involved in the regulation of physiological or pathological changes such as blood pressure regulation,neurodevelopment,tumor progression and other physiological or pathological changes,but its role in tumor immunity has not been reported.In this study,the regulatory role of NEDD4 L in tumor immunity and its mechanism were discussed,and the following results were obtained:1.NEDD4 L inhibits anti-tumor immune and increases the resistance to anti-tumor immunotherapy in melonama.The data showed that the expression of NEDD4 L was increased in melanoma and other tumors,and was negatively correlated with the survival and prognosis of melanoma patients.It was found that knockout NEDD4 L in B16F10 cells had different regulatory effects on the growth of B16F10 in immunodeficient nude mice and immunized normal C57 mice.knockout of NEDD4 L promoted the growth of B16F10 cells in nude mice.However,there was no significant effect on the growth of B16F10 cells in C57 mice.It was found that knockout of NEDD4 L did not affect the proliferation of B16F10 in vitro,but could promote the killing by T cells in vitro.Further in vivo experiments found that knockout NEDD4 L combined with anti-CTLA4 antibody immunotherapy showed a more significant growth inhibition effect on B16F10 than anti-CTLA4 antibody immunotherapy alone.These results suggest that NEDD4 L can inhibit the anti-tumor immune response,and has the potential to become a joint target of immune checkpoint blocking therapy.2.NEDD4 L maintains the protein expression level of PDL1 in tumor cells by ubiquitin modification of PDL1.We explored the mechanism of NEDD4 L promoting resistance to tumor immune.it was found that NEDD4 L maintained the expression of co-immunosuppressive molecule PDL1 protein through tumor intrinsic mechanism,and this regulation was mainly through post-transcriptional regulation mechanism.NEDD4 L could bind to PDL1 and promote its ubiquitin modification,and the promotion of PDL1 expression by NEDD4 L depended on its ubiquitin ligase activity.These results suggest that NEDD4 L can up-regulate the expression of PDL1 in tumor cells by ubiquitinating PDL1,which provides a possible explanation for the mechanism of NEDD4 L promoting tumor immune resistance.In this study,E3 ubiquitin ligase NEDD4 L was found to regulate the anti-tumor immune effect of the body,and its mechanism was preliminarily discussed.it was suggested that NEDD4 L could bind to PDL1 and modify it by ubiquitination,promoting the expression of PDL1 in tumor cells.The discovery of NEDD4 L involved in the regulation of tumor immunity not only enriches the understanding of the biological function of NEDD4 L,but also helps to improve the tumor immune regulation network.At the same time,this study also provides an idea for the subsequent design of anti-tumor target drugs and the development of new tumor immunotherapy strategies.