STING regulates BCR signaling in normal and malignant B cells

STING is an endoplasmic reticulum(ER)-resident protein critical for sensing cytoplasmic DNA and promoting the production of type Ⅰ interferons;however,the role of STING in B cell receptor(BCR)signaling remains unclear.We generated STING V154M knock-in mice and showed that B cells carrying constitutively activated STING specifically degraded membrane-bound IgM,Ig a and Igβ via SEL1L/HRD1-mediated ER-associated degradation(ERAD).B cells with activated STING were thus less capable of responding to BCR activation by phosphorylating Igα and Syk than those without activated STING.When immunized with T-independent antigens,STING V154M mice produced significantly fewer antigen-specific plasma cells and antibodies than immunized wild-type(WT)mice.We further generated B cell-specific STING^(KO) mice and showed that STING^(KO) B cells indeed responded to activation by transducing stronger BCR signals than their STING-proficient counterparts.When B cell-specific STING^(KO) mice were T-independently immunized,they produced significantly more antigen-specific plasma cells and antibodies than immunized STIN^(WT)mice.Since both human and m ouse IGHV-unmutated malignant chronic lymphocytic leukemia(CLL)cells downregulated the expression of STING,we explored whether STING downregulation could contribute to the well-established robust BCR signaling phenotype in malignant CLL cells.We generated a STING-deficient CLL mouse model and showed that STING-deficient CLL cells were indeed more responsive to BCR activation than their STING-proficient counterparts.These results revealed a novel B cell-intrinsic role of STING in negatively regulating BCR signaling in both normal and malignant B cells.

STING negatively regulates allogeneic T-cell responses by constraining antigen-presenting cell function

Stimulator of interferon genes(STING)-mediated innate immune activation plays a key role in tumor-and self-DNA-elicited antitumor immunity and autoimmunity.However,STING can also suppress tumor immunity and autoimmunity.STING signaling In host nonhematopoietic cells was reported to either protect against or promote graft-versus-host disease(GVHD),a major complication of allogeneic hematopoietic cell transplantation(allo-HCT).Host hematopoietic antigen-presenting cells(APCs)play key roles in donor T-cell priming during GVHD initiation.However,how STING regulates host hematopoietic APCs after allo-HCT remains unknown.We utilized murine models of allo-HCT to assess the role of STING in hematopoietic APCs.STING-deficient recipients developed more severe GVHD after major histocompatibility complex-mismatched allo-HCT.Using bone marrow chimeras,we found that STING deficiency in host hematopoietic cells was primarily responsible for exacerbating the disease.Furthermore,STING on host CD11c+cells played a dominant role in suppressing allogeneic T-cell responses.Mechanistically,STING deficiency resulted in increased survival,activation,and function of APCs,including macrophages and dendritic cells.Consistently,constitutive activation of STING attenuated the survival,activation,and function of APCs isolated from STING V154M knock-in mice.STING-deficient APCs augmented donor T-cell expansion,chemokine receptor expression,and migration into intestinal tissues,resulting in accelerated/exacerbated GVHD.Using pharmacologic approaches,we demonstrated that systemic administration of a STING agonist(bis-(3'-5')-cyclic dimeric guanosine monophosphate)to recipient mice before transplantation significantly reduced GVHD mortality.In conclusion,we revealed a novel role of STING in APC activity that dictates T-cell allogeneic responses and validated STING as a potential therapeutic target for controlling GVHD after allo-HCT.