The inhibitory NK receptor Ly49Q protects plasmacytoid dendritic cells from pyroptotic cell death.

Ly49Q is an ITIM-bearing MHC class I receptor that is highly expressed in plasmacytoid dendritic cells (pDCs). Ly49Q is required for the TLR9-mediated IFN-I production in pDCs, although the mechanism is not fully understood. We here demonstrate that Ly49Q protects pDCs from pyroptotic cell death induced by CpG oligodeoxynucleotides (CpG). In the Ly49Q-deficient (Klra17-/-) mouse spleen, the number of ssDNA-positive pDCs increased significantly after CpG treatment, strongly suggesting that Klra17-/- pDCs were susceptible to CpG-induced cell death. In Klra17-/- bone-marrow-derived dendritic cells (BMDCs), CpG-induced cell death was accompanied by increased cathepsin B leakage from the vesicular compartments into the cytoplasm. Concurrently, IL-1ß secretion increased in the CpG-treated Klra17-/- BMDCs, strongly suggesting that the CpG-induced cell death in these cells is pyroptotic in nature. Consistent with these observations, inhibiting cathepsin B or caspase 1 in CpG-stimulated Klra17-/- BMDCs reversed the increase in cell death. Pyroptotic cell death and IL-1ß secretion were also observed in BMDCs derived from transgenic mice expressing an ITIM-less Ly49Q (Ly49Q-YF Tg). CpG also increased the IL-1ß production and cell death in B2m-/- BMDCs. These results suggest that Ly49Q and MHC class I play important roles for protecting pyroptosis-like cell death of DCs by influencing lysosome state.

Predicting the Efficacy and Safety of TACTICs (Tumor Angiogenesis-Specific CAR-T Cells Impacting Cancers) Therapy for Soft Tissue Sarcoma Patients.

Soft tissue sarcomas (STSs) are heterogeneous and aggressive malignancies with few effective therapies available. We have developed T cells expressing a vascular endothelial growth factor receptor 2 (VEGFR2)-specific chimeric antigen receptor (CAR) to establish a tumor angiogenesis-specific CAR-T cells impacting cancers (TACTICs) therapy. In this study, we optimized the manufacturing and transportation of mRNA-transfected anti-VEGFR2 CAR-T cells and collected information that allowed the extrapolation of the efficacy and safety potential of TACTICs therapy for STS patients. Although 5-methoxyuridines versus uridines did not improve CAR-mRNA stability in T cells, the utilization of CleanCap as a 5' cap-structure extended the CAR expression level, increasing VEGFR2-specific cytotoxicity. Furthermore, 4 °C preservation conditions did not affect the viability/cytotoxicity of CAR-T cells, contrarily to a freeze-thaw approach. Importantly, immunohistochemistry showed that most of the STS patients' specimens expressed VEGFR2, suggesting a great potential of our TACTICs approach. However, VEGFR2 expression was also detected in normal tissues, stressing the importance of the application of a strict monitoring schedule to detect (and respond to) the occurrence of adverse effects in clinics. Overall, our results support the development of a "first in humans" study to evaluate the potential of our TACTICs therapy as a new treatment option for STSs.

Blockade of N-Glycosylation Promotes Antitumor Immune Response of T Cells.

Adoptive cellular therapy and its derivative, chimeric AgR T cell therapy, have achieved significant progress against cancer. Major barriers persist, however, including insufficient induction of cytotoxic T cells and exhaustion of tumor-infiltrating lymphocytes. In this study, we discovered a new role for 2-deoxy-d-glucose (2DG) in enhancing the antitumor activity of human T cells against NKG2D ligand-expressing tumor cells. Human T cells treated with 2DG upregulated the NK-specific transcription factors TOX2 and EOMES, thereby acquiring NK cell properties, including high levels of perforin/granzyme and increased sensitivity to IL-2. Notably, rather than inhibiting glycolysis, 2DG modified N-glycosylation, which augmented antitumor activity and cell surface retention of IL-2R of T cells. Moreover, 2DG treatment prevented T cells from binding to galectin-3, a potent tumor Ag associated with T cell anergy. Our results, therefore, suggest that modifying N-glycosylation of T cells with 2DG could improve the efficacy of T cell-based immunotherapies against cancer.

LRRK2 regulates endoplasmic reticulum-mitochondrial tethering through the PERK-mediated ubiquitination pathway.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common cause of familial Parkinson's disease (PD). Impaired mitochondrial function is suspected to play a major role in PD. Nonetheless, the underlying mechanism by which impaired LRRK2 activity contributes to PD pathology remains unclear. Here, we identified the role of LRRK2 in endoplasmic reticulum (ER)-mitochondrial tethering, which is essential for mitochondrial bioenergetics. LRRK2 regulated the activities of E3 ubiquitin ligases MARCH5, MULAN, and Parkin via kinase-dependent protein-protein interactions. Kinase-active LRRK2(G2019S) dissociated from these ligases, leading to their PERK-mediated phosphorylation and activation, thereby increasing ubiquitin-mediated degradation of ER-mitochondrial tethering proteins. By contrast, kinase-dead LRRK2(D1994A)-bound ligases blocked PERK-mediated phosphorylation and activation of E3 ligases, thereby increasing the levels of ER-mitochondrial tethering proteins. Thus, the role of LRRK2 in the ER-mitochondrial interaction represents an important control point for cell fate and pathogenesis in PD.

Natural killer cells impede the engraftment of cardiomyocytes derived from induced pluripotent stem cells in syngeneic mouse model.

Transplantation of cardiomyocytes derived from induced pluripotent stem cell (iPSC-CMs) is a promising approach for increasing functional CMs during end-stage heart failure. Although major histocompatibility complex (MHC) class I matching between donor cells and recipient could reduce acquired immune rejection, innate immune responses may have negative effects on transplanted iPSC-CMs. Here, we demonstrated that natural killer cells (NKCs) infiltrated in iPSC-CM transplants even in a syngeneic mouse model. The depletion of NKCs using an anti-NKC antibody rescued transplanted iPSC-CMs, suggesting that iPSC-CMs activated NKC-mediated innate immunity. Surprisingly, iPSC-CMs lost inhibitory MHCs but not activating ligands for NKCs. Re-expression of MHC class I induced by IFN-γ as well as suppression of activating ligands by an antibody rescued the transplanted iPSC-CMs. Thus, NKCs impede the engraftment of transplanted iPSC-CMs because of lost MHC class I, and our results provide a basis for an approach to improve iPSC-CM engraftment.

Immunological quality and performance of tumor vessel-targeting CAR-T cells prepared by mRNA-EP for clinical research.

We previously reported that tumor vessel-redirected T cells, which were genetically engineered with chimeric antigen receptor (CAR) specific for vascular endothelial growth factor receptor 2 (VEGFR2), demonstrated significant antitumor effects in various murine solid tumor models. In the present study, we prepared anti-VEGFR2 CAR-T cells by CAR-coding mRNA electroporation (mRNA-EP) and analyzed their immunological characteristics and functions for use in clinical research. The expression of anti-VEGFR2 CAR on murine and human T cells was detected with approximately 100% efficiency for a few days, after peaking 6-12 hours after mRNA-EP. Triple transfer of murine anti-VEGFR2 CAR-T cells into B16BL6 tumor-bearing mice demonstrated an antitumor effect comparable to that for the single transfer of CAR-T cells engineered with retroviral vector. The mRNA-EP did not cause any damage or defects to human T-cell characteristics, as determined by viability, growth, and phenotypic parameters. Additionally, two kinds of human anti-VEGFR2 CAR-T cells, which expressed different CAR construction, differentiated to effector phase with cytokine secretion and cytotoxic activity in antigen-specific manner. These results indicate that our anti-VEGFR2 CAR-T cells prepared by mRNA-EP have the potential in terms of quality and performance to offer the prospect of safety and efficacy in clinical research as cellular medicine.

Leucine-Rich Repeat Kinase 1 Regulates Autophagy through Turning On TBC1D2-Dependent Rab7 Inactivation.

Autophagy is a conserved process that enables catabolic and degradative pathways. Rab family proteins, which are active in the GTP-bound form, regulate the transport and fusion of autophagosomes. However, it remains unclear how each cycle of Rab activation and inactivation is precisely regulated. Here, we show that leucine-rich repeat kinase 1 (LRRK1) regulates autophagic flux by controlling Rab7 activity in autolysosome formation. Upon induction of autophagy, LRRK1 was recruited via an association with VAMP7 to the autolysosome, where it activated the Rab7 GTPase-activating protein (GAP) TBC1D2, thereby switching off Rab7 signaling. Consistent with this model, LRRK1 deletion caused mice to be vulnerable to starvation and disrupted autolysosome formation, as evidenced by the accumulation of enlarged autolysosomes with undegraded LC3-II and persistently high levels of Rab7-GTP. This defect in autophagic flux was partially rescued by a mutant form of TBC1D2 with elevated Rab7-GAP activity. Thus, the spatiotemporal regulation of Rab7 activity during tunicamycin-induced autophagy is regulated by LRRK1.

The solute carrier family 15A4 regulates TLR9 and NOD1 functions in the innate immune system and promotes colitis in mice.

BACKGROUND & AIMS: Solute carrier family 15 (SLC15) A4 is a proton-coupled histidine and oligopeptide cotransporter expressed by the immune and nervous systems and associated with disorders such as inflammatory bowel diseases and systemic lupus erythematosus. High levels of SLC15A4 transcripts were observed in human antigen-presenting cells, including dendritic cells, activated macrophages, and B cells. However, the roles of SLC15A4 in the immune regulation are not known. We investigated the function of SLC15A4 in the innate immune system. METHODS: We created SLC15A4-deficient (SLC15A4(-/-)) mice and compared Toll-like receptor 9 and NOD1-dependent innate immune responses between SLC15A4(-/-) and control (SLC15A4(+/+)) mice. RESULTS: SLC15A4 deficiency impaired CpG-induced production of interleukin-12, interleukin-15, and interleukin-18 by dendritic cells. Correspondingly, SLC15A4(-/-) mice developed a less severe form of Th1-dependent colitis than SLC15A4(+/+) mice. Increased lysosomal histidine, in the absence of SLC15A4, appears to negatively regulate Toll-like receptor 9 function by inhibiting the proteolytic activities of cathepsins B and L. SLC15A4(-/-) mice also had a severe defect in NOD1-dependent cytokine production, indicating that SLC15A4 functions as a transporter of the NOD1 ligand. CONCLUSIONS: SLC15A4 promotes colitis through Toll-like receptor 9 and NOD1-dependent innate immune responses. Histidine homeostasis within intracellular compartments is important for eliciting effective innate immune responses.

The innate immune system in host mice targets cells with allogenic mitochondrial DNA.

Mitochondrial DNA (mtDNA) has been proposed to be involved in respiratory function, and mtDNA mutations have been associated with aging, tumors, and various disorders, but the effects of mtDNA imported into transplants from different individuals or aged subjects have been unclear. We examined this issue by generating trans-mitochondrial tumor cells and embryonic stem cells that shared the syngenic C57BL/6 (B6) strain-derived nuclear DNA background but possessed mtDNA derived from allogenic mouse strains. We demonstrate that transplants with mtDNA from the NZB/B1NJ strain were rejected from the host B6 mice, not by the acquired immune system but by the innate immune system. This rejection was caused partly by NK cells and involved a MyD88-dependent pathway. These results introduce novel roles of mtDNA and innate immunity in tumor immunology and transplantation medicine.

The Ly49Q receptor plays a crucial role in neutrophil polarization and migration by regulating raft trafficking.

Neutrophils rapidly undergo polarization and directional movement to infiltrate the sites of infection and inflammation. Here, we show that an inhibitory MHC I receptor, Ly49Q, was crucial for the swift polarization of and tissue infiltration by neutrophils. During the steady state, Ly49Q inhibited neutrophil adhesion by preventing focal-complex formation, likely by inhibiting Src and PI3 kinases. However, in the presence of inflammatory stimuli, Ly49Q mediated rapid neutrophil polarization and tissue infiltration in an ITIM-domain-dependent manner. These opposite functions appeared to be mediated by distinct use of effector phosphatase SHP-1 and SHP-2. Ly49Q-dependent polarization and migration were affected by Ly49Q regulation of membrane raft functions. We propose that Ly49Q is pivotal in switching neutrophils to their polarized morphology and rapid migration upon inflammation, through its spatiotemporal regulation of membrane rafts and raft-associated signaling molecules.

Spatiotemporal regulation of intracellular trafficking of Toll-like receptor 9 by an inhibitory receptor, Ly49Q.

Toll-like receptor (TLR) 9 recognizes unmethylated microorganismal cytosine guanine dinucleotide (CpG) DNA and elicits innate immune responses. However, the regulatory mechanisms of the TLR signaling remain elusive. We recently reported that Ly49Q, an immunoreceptor tyrosine-based inhibitory motif-bearing inhibitory receptor belonging to the natural killer receptor family, is crucial for TLR9-mediated type I interferon production by plasmacytoid dendritic cells. Ly49Q is expressed in plasmacytoid dendritic cells, macrophages, and neutrophils, but not natural killer cells. In this study, we showed that Ly49Q regulates TLR9 signaling by affecting endosome/lysosome behavior. Ly49Q colocalized with CpG in endosome/lysosome compartments. Cells lacking Ly49Q showed a disturbed redistribution of TLR9 and CpG. In particular, CpG-induced tubular endolysosomal extension was impaired in the absence of Ly49Q. Consistent with these findings, cells lacking Ly49Q showed impaired cytokine production in response to CpG-oligodeoxynucleotide. Our data highlight a novel mechanism by which TLR9 signaling is controlled through the spatiotemporal regulation of membrane trafficking by the immunoreceptor tyrosine-based inhibitory motif-bearing receptor Ly49Q.

Efficient priming and expansion of antigen-specific CD8+ T cells by a novel cell-based artificial APC.

The ex vivo priming and expansion of human CTL by APC, such as autologous monocyte-derived dendritic cells (DC), has the potential for use in immunotherapy for infectious diseases and cancer. To overcome the difficulty of obtaining sufficient number of autologous DC from patients, we have developed cell-based artificial APC (aAPC), designated Med-APC. These aAPC rapidly activate and expand the corresponding Ag-specific CD8+ T cells when pulsed with CTL epitope peptide(s) as efficiently as mature DC (mDC). We have also shown that Med-APC possess an innate cellular machinery that is sufficient to support the processing of complete Ag into immunodominant peptides, which considerably extends the usefulness of this technology. In addition, we have developed a novel expression vector system that expresses ubiquitinated Ag, resulting in an enhanced APC function of this system. Genetically encoded Ag can be easily introduced into Med-APC by transfection with this vector. Med-APC transfected with ubiquitinated Ag can efficiently expand the corresponding Ag-specific CTL without exogenous peptides. Therefore, Med-APC may have important therapeutic implications for adoptive immunotherapy and can be used for the detection of Ag-specific CTL for immunomonitoring.

Effect of PCB-126 on intracellular accumulation and transepithelial transport of vinblastine in LLC-PK1 and its transformant cells expressing human P-glycoprotein.

The effects of 3, 3', 4, 4', 5-pentachlorobiphenyl (PCB-126), which is the most toxic congener of coplanar polychlorinated biphenyls (Co-PCBs), on intracellular accumulation and transepithelial transport of vinblastine were examined in porcine kidney cells, LLC-PK1, and its transformant cells expressing human P-glycoprotein (LLC-MDR1). The accumulation decreased less than one-tenth in LLC-MDR1 compared to LLC-PK1. In both cells, the accumulation increased with the addition of PCB-126 and cyclosporine A (CYA), which are P-glycoprotein modulators, though the magnitudes were different in these two cell groups as well as for these two chemicals. Thus, PCB-126 might inhibit extrusion of vinblastine through the drug extrusion system as does CYA. In both the cells, there might be an endogenous drug extrusion system other than P-glycoprotein that was inhibited by CYA or PCB-126. The net basal-to-apical transepithelial transport of vinblastine increased 1.7-fold more in LLC-MDR1 than in LLC-PK1. By adding PCB-126 on the apical side, the transport was greatly decreased by -76% in the monolayer of both cells. By adding PCB-126 and CYA on the basal side in LLC-MDR1 monolayer, the transports increased -1.7-fold, so that PCB-126 might inhibit the extrusion of vinblastine on both the apical and basal sides. One of the causes to be considered for the adverse effects of Co-PCBs, in addition to the binding with an aryl hydrocarbon receptor, might be the modification of drug transport by its interaction with the drug transport system.

$3,3',4,4',5$ -Pentachlorobiphenyl Inhibits Drug Efflux Through P-Glycoprotein in KB-3 Cells Expressing Mutant Human P-Glycoprotein.

The effects on the drug efflux of $3,3',4,4',5$ -pentachlorobiphenyl (PCB-126), the most toxic of all coplanar polychlorinated biphenyls (Co-PCBs), were examined in KB-3 cells expressing human wild-type and mutant P-glycoprotein in which the 61st amino acid was substituted for serine or phenylalanine ( ${\text{KB3 - Phe}};{61} $ ). In the cells expressing P-glycoproteins, accumulations of vinblastine and colchicine decreased form 85% to 92% and from 62% to 91%, respectively, and the drug tolerances for these chemicals were increased. In ${\text{KB3 - Phe}};{61} $, the decreases in drug accumulation were inhibited by adding PCB-126 in a way similar to that with cyclosporine A: by adding 1 $\mu$ M PCB-126, the accumulations of vinblastine and colchicine increased up to 3.3- and 2.3-fold, respectively. It is suggested that PCB-126 decreased the drug efflux by inhibiting the P-glycoprotein in ${\text{KB3 - Phe}};{61} $. Since there were various P-glycoproteins and many congeners of Co-PCBs, this inhibition has to be considered a new cause of the toxic effects of Co-PCBs.

Transepithelial transport and cellular accumulation of steroid hormones and polychlorobiphenyl in porcine kidney cells expressed with human P-glycoprotein.

Endocrine disrupters such as sex hormone-like chemicals and the non-physiological ligands for aryl hydrocarbon receptor (AhR) exert many adverse biological effects. The ligands for AhR disturb gene expression downstream of the gene induced by estrogen receptor at a very low concentration. Thus, transepithelial transport and cellular accumulation of cortisol (COR) and estrogen as congeners of sex hormone-like chemicals, and 3,3',4,4'-tetrachlorobiphenyl (TeCB) as one of the ligands for AhR were examined in a monolayer of porcine kidney cells transfected with human P-glycoprotein (LLC-COL). The net basal-to-apical transport of COR increased in LLC-COL compared to that in the wild type cells (LLC-PKI) the same as in vinblastine, whereas the net transport of estradiol (EST) was not detected in either cell group. Though the diffusion transports of EST for both directions, basal-to-apical and apical-to-basal, were higher than that of COR, cellular accumulation of EST was higher than that of COR. Transepithelial transport of TeCB was very low and the net basal-to-apical transport was not detected, while it was highly accumulated in the epithelial cells. The accumulation was slightly higher in LLC-COL than in LLC-PKI at high dose.