Ena/VASP Protein-Mediated Actin Polymerization Contributes to Naïve CD8+ T Cell Activation and Expansion by Promoting T Cell-APC Interactions In Vivo.

Naïve T cell activation in secondary lymphoid organs such as lymph nodes (LNs) occurs upon recognition of cognate antigen presented by antigen presenting cells (APCs). T cell activation requires cytoskeleton rearrangement and sustained interactions with APCs. Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are a family of cytoskeletal effector proteins responsible for actin polymerization and are frequently found at the leading edge of motile cells. Ena/VASP proteins have been implicated in motility and adhesion in various cell types, but their role in primary T cell interstitial motility and activation has not been explored. Our goal was to determine the contribution of Ena/VASP proteins to T cell-APC interactions, T cell activation, and T cell expansion in vivo. Our results showed that naïve T cells from Ena/VASP-deficient mice have a significant reduction in antigen-specific T cell accumulation following Listeria monocytogenes infection. The kinetics of T cell expansion impairment were further confirmed in Ena/VASP-deficient T cells stimulated via dendritic cell immunization. To investigate the cause of this T cell expansion defect, we analyzed T cell-APC interactions in vivo by two-photon microscopy and observed fewer Ena/VASP-deficient naïve T cells interacting with APCs in LNs during priming. We also determined that Ena/VASP-deficient T cells formed conjugates with significantly less actin polymerization at the T cell-APC synapse, and that these conjugates were less stable than their WT counterparts. Finally, we found that Ena/VASP-deficient T cells have less LFA-1 polarized to the T cell-APC synapse. Thus, we conclude that Ena/VASP proteins contribute to T cell actin remodeling during T cell-APC interactions, which promotes the initiation of stable T cell conjugates during APC scanning. Therefore, Ena/VASP proteins are required for efficient activation and expansion of T cells in vivo.

Mycobacterium vaccae immunization in rats ameliorates features of age-associated microglia activation in the amygdala and hippocampus.

Aging and reduced exposure to environmental microbes can both potentiate neuroinflammatory responses. Prior studies indicate that immunization with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), in aged rats limits neuroimmune activation and cognitive impairments. However, the mechanisms by which M. vaccae immunization ameliorates age-associated neuroinflammatory "priming" and whether microglia are a primary target remain unclear. Here, we investigated whether M. vaccae immunization protects against microglia morphological changes in response to aging. Adult (3 mos) and aged (24 mos) Fisher 344 × Brown Norway rats were immunized with either M. vaccae or vehicle once every week for 3 weeks. Aging led to elevated Iba1 immunoreactivity, microglial density, and deramification of microglia processes in the hippocampus and amygdala but not other brain regions. Additionally, aged rats exhibited larger microglial somas in the dorsal hippocampus, suggestive of a more activated phenotype. Notably, M. vaccae treatment ameliorated indicators of microglia activation in both the amygdala and hippocampus. While changes in morphology appeared to be region-specific, gene markers indicative of microglia activation were upregulated by age and lowered in response to M. vaccae in all brain regions evaluated. Taken together, these data suggest that peripheral immunization with M. vaccae quells markers of age-associated microglia activation.

The ERM protein moesin regulates natural killer cell homeostasis in vivo.

Moesin is a member of the ezrin-radixin-moesin (ERM) family of proteins that link plasma membrane proteins with actin filaments in the cell cortex. Hemizygous mutations in the X-linked moesin gene are associated with primary immunodeficiency with T and B cell lymphopenia, which also affects natural killer (NK) cells in most cases. We previously showed that moesin deficiency in mice substantially affects lymphocyte homeostasis, but its impact on NK cells remains unexplored. Here, we found that in moesin-deficient mice, NK cells were decreased in the peripheral blood and bone marrow but increased in the spleen. Analysis of female heterozygous mice showed a selective advantage for moesin-expressing NK cells in the blood. Moesin-deficient NK cells exhibited increased cell death and impaired signaling in response to IL-15, suggesting that moesin regulates NK cell survival through IL-15-mediated signaling. Our findings thus identify moesin as an NK cell homeostasis regulator in vivo.

Novel Autoantibodies in Idiopathic Small Fiber Neuropathy.

OBJECTIVE: Small fiber neuropathy (SFN) is clinically and etiologically heterogeneous. Although autoimmunity has been postulated to be pathophysiologically important in SFN, few autoantibodies have been described. We aimed to identify autoantibodies associated with idiopathic SFN (iSFN) by a novel high-throughput protein microarray platform that captures autoantibodies expressed in the native conformational state. METHODS: Sera from 58 SFN patients and 20 age- and gender-matched healthy controls (HCs) were screened against >1,600 immune-related antigens. Fluorescent unit readout and postassay imaging were performed, followed by composite data normalization and protein fold change (pFC) analysis. Analysis of an independent validation cohort of 33 SFN patients against the same 20 HCs was conducted to identify reproducible proteins in both cohorts. RESULTS: Nine autoantibodies were screened with statistical significance and pFC criteria in both cohorts, with at least 50% change in serum levels. Three proteins showed consistently high fold changes in main and validation cohorts: MX1 (FC = 2.99 and 3.07, respectively, p = 0.003, q = 0.076), DBNL (FC = 2.11 and 2.16, respectively, p = 0.009, q < 0.003), and KRT8 (FC = 1.65 and 1.70, respectively, p = 0.043, q < 0.003). Further subgroup analysis into iSFN and SFN by secondary causes (secondary SFN) in the main cohort showed that MX1 is higher in iSFN compared to secondary SFN (FC = 1.61 vs 0.106, p = 0.009). INTERPRETATION: Novel autoantibodies MX1, DBNL, and KRT8 are found in iSFN. MX1 may allow diagnostic subtyping of iSFN patients. ANN NEUROL 2022;91:66-77.

Supervillin Contributes to LPS-induced Inflammatory Response in THP-1 Cell-derived Macrophages.

Supervillin (SVIL) is an actin-binding and membrane-associated protein, which belongs to villin/gelsolin family. It has been reported that SVIL was involved in the regulation of macrophages' movement and lipopolysaccharide (LPS) increased the SVIL mRNA expression in neutrophils, but the underlying mechanisms remain unknown. This work investigated the underlying molecular mechanisms of LPS regulating SVIL expression in macrophages and hence the possible role of SVIL in LPS-induced inflammation. We found that in THP-1-derived macrophages, LPS obviously increased SVIL mRNA and protein expression. Inhibition of TLR4 by Resatorvid (Res) remarkably reversed the LPS-induced SVIL expression. Additionally, inhibition of ERK1/2 signaling pathway (by U0126 or GDC-0994) and NF-κB (by BAY) significantly reduced the LPS-induced SVIL expression. Interestingly, down-regulation of SVIL by SVIL-specific shRNAs significantly attenuated the expression of IL-6, IL-1ß & TNF-α induced by LPS at both mRNA and protein levels. Furthermore, we also observed that SVIL knockdown decreased the proportion of cells in G2/M phase and increased the proportion of cells in S & G0-1 phase of THP-1 derived macrophages, but did not influence the cell viability. Taken together, we demonstrated that LPS induced the expression of SVIL via activating TLR4/NF-κB and ERK1/2 MAPK pathways, and SVIL participated in the inflammatory response of LPS-induced IL-6, IL-1ß and TNF-α upregulation in macrophages.

Bioinformatic Analysis of Prognostic and Immune-Related Genes in Pancreatic Cancer.

Pancreatic cancer (PC) is a malignant tumor with poor prognosis. The poor effect of surgery and chemotherapy makes the research of immunotherapy target molecules significant. Therefore, identifying the new molecular targets of PC is important for patients. In our study, we systematically analyzed molecular correlates of pancreatic cancer by bioinformatic analysis. We characterized differentially expressed analysis based on the TCGA pancreatic cancer dataset. Then, univariate Cox regression was employed to screen out overall survival- (OS-) related DEGs. Based on these genes, we established a risk signature by the multivariate Cox regression model. The ICGC cohort and GSE62452 cohort were used to validate the reliability of the risk signature. The impact of T lymphocyte-related genes from risk signature was confirmed in PC. Here, we observed the correlation between the T lymphocyte-related genes and the expression level of targeted therapy. We established a five-mRNA (LY6D, ANLN, ZNF488, MYEOV, and SCN11A) prognostic risk signature. Next, we identified ANLN and MYEOV that were associated with T lymphocyte infiltrations (P < 0.05). High ANLN and MYEOV expression levels had a poorer prognosis in decreased T lymphocyte subgroup in PC. Correlation analysis between ANLN and MYEOV and immunomodulators showed that ANLN and MYEOV may have potential value in pancreatic cancer immunotherapy.

Central Nervous System-Infecting Pathogens Escherichia coli and Cryptococcus neoformans Exploit the Host Pdlim2 for Intracellular Traversal and Exocytosis in the Blood-Brain Barrier.

Microbial penetration of the blood-brain barrier, a prerequisite for the development of central nervous system (CNS) infection, involves microbial invasion, intracellular traversal, and exocytosis. Microbial invasion of the blood-brain barrier has been investigated, but the molecular basis for microbial traversal and exit from the blood-brain barrier remains unknown. We performed transcriptome analysis of human brain microvascular endothelial cells (HBMEC) infected with Escherichia coli and Cryptococcus neoformans, representative bacterial and fungal pathogens common in CNS infections. Among the targets upregulated in response to E. coli and C. neoformans infection, PDLIM2 was knocked down by small hairpin RNA (shRNA) in HBMEC for further investigation. We demonstrated that Pdlim2 specifically regulated microbial traversal and exit from HBMEC by assessing microbial invasion, transcytosis, intracellular multiplication, and egression. Additionally, the defective exocytosis of internalized E. coli cells from the PDLIM2 shRNA knockdown cells was restored by treatment with a calcium ionophore (ionomycin). Moreover, we performed proximity-dependent biotin labeling with the biotin ligase BioID2 and identified 210 potential Pdlim2 interactors. Among the nine Pdlim2 interactors enriched in response to both E. coli and C. neoformans infection, we selected MPRIP and showed that HBMEC with knockdown of MPRIP mimicked the phenotype of PDLIM2 knockdown cells. These results suggest that the CNS-infecting microbes hijack Pdlim2 and Mprip for intracellular traversal and exocytosis in the blood-brain barrier.

The Role of Glycosyltransferases in Colorectal Cancer.

Colorectal cancer (CRC) is one of the main causes of cancer death in the world. Post-translational modifications (PTMs) have been extensively studied in malignancies due to its relevance in tumor pathogenesis and therapy. This review is focused on the dysregulation of glycosyltransferase expression in CRC and its impact in cell function and in several biological pathways associated with CRC pathogenesis, prognosis and therapeutic approaches. Glycan structures act as interface molecules between cells and their environment and in several cases facilitate molecule function. CRC tissue shows alterations in glycan structures decorating molecules, such as annexin-1, mucins, heat shock protein 90 (Hsp90), ß1 integrin, carcinoembryonic antigen (CEA), epidermal growth factor receptor (EGFR), insulin-like growth factor-binding protein 3 (IGFBP3), transforming growth factor beta (TGF-ß) receptors, Fas (CD95), PD-L1, decorin, sorbin and SH3 domain-containing protein 1 (SORBS1), CD147 and glycosphingolipids. All of these are described as key molecules in oncogenesis and metastasis. Therefore, glycosylation in CRC can affect cell migration, cell-cell adhesion, actin polymerization, mitosis, cell membrane repair, apoptosis, cell differentiation, stemness regulation, intestinal mucosal barrier integrity, immune system regulation, T cell polarization and gut microbiota composition; all such functions are associated with the prognosis and evolution of the disease. According to these findings, multiple strategies have been evaluated to alter oligosaccharide processing and to modify glycoconjugate structures in order to control CRC progression and prevent metastasis. Additionally, immunotherapy approaches have contemplated the use of neo-antigens, generated by altered glycosylation, as targets for tumor-specific T cells or engineered CAR (Chimeric antigen receptors) T cells.

Hierarchical cell-type-specific functions of caspase-11 in LPS shock and antibacterial host defense.

Caspase-11 sensing of intracellular lipopolysaccharide (LPS) plays critical roles during infections and sepsis. However, the key cell types that sense intracellular LPS and their contributions to the host responses at the organismal level are not completely clear. Here, we show that macrophage/monocyte-specific caspase-11 plays a dominant role in mediating the pathological manifestations of endotoxemia, including gasdermin D (GSDMD) activation, interleukin (IL)-1ß, IL-18, and damage-associated molecular pattern (DAMP) release, tissue damage, and death. Surprisingly, caspase-11 expression in CD11c+ cells and intestinal epithelial cells (IECs) plays minor detrimental roles in LPS shock. In contrast, caspase-11 expression in neutrophils is dispensable for LPS-induced lethality. Importantly, caspase-11 sensing of intracellular LPS in LyzM+ myeloid cells and MRP8+ neutrophils, but not CD11c+ cells and IECs, is necessary for bacterial clearance and host survival during intracellular bacterial infection. Thus, we reveal hierarchical cell-type-specific roles of caspase-11 that govern the host-protective and host-detrimental functions of the cytosolic LPS surveillance.

Novel Mouse Model Reveals That Serine Phosphorylation of L-Plastin Is Essential for Effective Splenic Clearance of Pneumococcus.

Asplenia imparts susceptibility to life-threatening sepsis with encapsulated bacteria, such as the pneumococcus. However, the cellular components within the splenic environment that guard against pneumococcal bacteremia have not been defined. The actin-bundling protein L-plastin (LPL) is essential for the generation of marginal zone B cells and for anti-pneumococcal host defense, as revealed by a mouse model of genetic LPL deficiency. In independent studies, serine phosphorylation of LPL at residue 5 (S5) has been described as a key "switch" in regulating LPL actin binding and subsequent cell motility, although much of the data are correlative. To test the importance of S5 phosphorylation in LPL function, and to specifically assess the requirement of LPL S5 phosphorylation in anti-pneumococcal host defense, we generated the "S5A" mouse, expressing endogenous LPL bearing a serine-to-alanine mutation at this position. S5A mice were bred to homozygosity, and LPL was expressed at levels equivalent to wild-type, but S5 phosphorylation was absent. S5A mice exhibited specific impairment in clearance of pneumococci following i.v. challenge, with 10-fold-higher bacterial bloodstream burden 24 h after challenge compared with wild-type or fully LPL-deficient animals. Defective bloodstream clearance correlated with diminished population of marginal zone macrophages and with reduced phagocytic capacity of multiple innate immune cells. Development and function of other tested leukocyte lineages, such as T and B cell motility and activation, were normal in S5A mice. The S5A mouse thus provides a novel system in which to elucidate the precise molecular control of critical immune cell functions in specific host-pathogen defense interactions.

Cell-permeable transgelin-2 as a potent therapeutic for dendritic cell-based cancer immunotherapy.

BACKGROUND: Transgelin-2 is a 22 kDa actin-binding protein that has been proposed to act as an oncogenic factor, capable of contributing to tumorigenesis in a wide range of human malignancies. However, little is known whether this tiny protein also plays an important role in immunity, thereby keeping body from the cancer development and metastasis. Here, we investigated the functions of transgelin-2 in dendritic cell (DC) immunity. Further, we investigated whether the non-viral transduction of cell-permeable transgelin-2 peptide potentially enhance DC-based cancer immunotherapy. METHODS: To understand the functions of transgelin-2 in DCs, we utilized bone marrow-derived DCs (BMDCs) purified from transgelin-2 knockout (Tagln2-/-) mice. To observe the dynamic cellular mechanism of transgelin-2, we utilized confocal microscopy and flow cytometry. To monitor DC migration and cognate T-DC interaction in vivo, we used intravital two-photon microscopy. For the solid and metastasis tumor models, OVA+ B16F10 melanoma were inoculated into the C57BL/6 mice via intravenously (i.v.) and subcutaneously (s.c.), respectively. OTI TCR T cells were used for the adoptive transfer experiments. Cell-permeable, de-ubiquitinated recombinant transgelin-2 was purified from Escherichia coli and applied for DC-based adoptive immunotherapy. RESULTS: We found that transgelin-2 is remarkably expressed in BMDCs during maturation and lipopolysaccharide activation, suggesting that this protein plays a role in DC-based immunity. Although Tagln2-/- BMDCs exhibited no changes in maturation, they showed significant defects in their abilities to home to draining lymph nodes (LNs) and prime T cells to produce antigen-specific T cell clones, and these changes were associated with a failure to suppress tumor growth and metastasis of OVA+ B16F10 melanoma cells in mice. Tagln2-/- BMDCs had defects in filopodia-like membrane protrusion and podosome formation due to the attenuation of the signals that modulate actin remodeling in vitro and formed short, unstable contacts with cognate CD4+ T cells in vivo. Strikingly, non-viral transduction of cell-permeable, de-ubiquitinated recombinant transgelin-2 potentiated DC functions to suppress tumor growth and metastasis. CONCLUSION: This work demonstrates that transgelin-2 is an essential protein for both cancer and immunity. Therefore, transgelin-2 can act as a double-edged sword depending on how we apply this protein to cancer therapy. Engineering and clinical application of this protein may unveil a new era in DC-based cancer immunotherapy. Our findings indicate that cell-permeable transgelin-2 have a potential clinical value as a cancer immunotherapy based on DCs.

Calponin and MUC6 complement inhibin as diagnostic immunomarkers of serous cystadenoma in endoscopic ultrasound-guided aspiration/biopsy specimens.

AIMS: Because serous cystadenoma (SCA) does not usually require excision, it is critical to distinguish it from differential diagnoses which do, especially neuroendocrine tumour (NET). The gold standard for diagnosing SCA is assessment of endoscopic ultrasound-guided fine needle aspiration/biopsy (EUS-FNAB) material. Inhibin immunohistochemistry aids this assessment, but such positivity is not absolutely sensitive or specific to SCA. The following is the largest known study of SCA EUS-FNAB specimens and the first to compare four potential SCA immunomarkers between themselves and inhibin, compared against NET. METHODS AND RESULTS: Immunohistochemistry for calponin, mucin 6 (MUC6), glucose transporter 1 (GLUT1) and vascular endothelial growth factor A (VEGFA) was performed on 30 EUS-FNAB and three resection specimens of SCA and 32 EUS-FNAB specimens of NET. GLUT1 and VEGFA were suboptimal as diagnostic immunomarkers of SCA, being expressed by 10 and 44% of NETs, respectively. Further, their expression by cellular constituents of blood which often contaminate EUS-FNAB specimens hampered identification of neoplastic cells, especially in hypocellular samples. While 19% of NETs showed nuclear MUC6 positivity, cytoplasmic expression of the protein showed 100% specificity and sensitivity as an SCA marker. However, assessing MUC6 in EUS-FNAB specimens must also consider the protein's focal expression in physiological pancreatic, gastric or duodenal tissues, which can contaminate these specimens. Calponin was less sensitive (71% versus 100%) but more specific (100% versus 91%) than inhibin, although easier to assess in EUS-FNAB specimens than MUC6. CONCLUSIONS: Of the four potential immunomarkers of SCA suggested by the existing literature, calponin and MUC6 are useful complementary studies to inhibin for application to EUS-FNAB specimens.

The RNA helicase Dhx15 mediates Wnt-induced antimicrobial protein expression in Paneth cells.

RNA helicases play roles in various essential biological processes such as RNA splicing and editing. Recent in vitro studies show that RNA helicases are involved in immune responses toward viruses, serving as viral RNA sensors or immune signaling adaptors. However, there is still a lack of in vivo data to support the tissue- or cell-specific function of RNA helicases owing to the lethality of mice with complete knockout of RNA helicases; further, there is a lack of evidence about the antibacterial role of helicases. Here, we investigated the in vivo role of Dhx15 in intestinal antibacterial responses by generating mice that were intestinal epithelial cell (IEC)-specific deficient for Dhx15 (Dhx15 f/f Villin1-cre, Dhx15ΔIEC). These mice are susceptible to infection with enteric bacteria Citrobacter rodentium (C. rod), owing to impaired α-defensin production by Paneth cells. Moreover, mice with Paneth cell-specific depletion of Dhx15 (Dhx15 f/f Defensinα6-cre, Dhx15ΔPaneth) are more susceptible to DSS (dextran sodium sulfate)-induced colitis, which phenocopy Dhx15ΔIEC mice, due to the dysbiosis of the intestinal microbiota. In humans, reduced protein levels of Dhx15 are found in ulcerative colitis (UC) patients. Taken together, our findings identify a key regulator of Wnt-induced α-defensins in Paneth cells and offer insights into its role in the antimicrobial response as well as intestinal inflammation.

A Murine Model of X-Linked Moesin-Associated Immunodeficiency (X-MAID) Reveals Defects in T Cell Homeostasis and Migration.

X-linked moesin associated immunodeficiency (X-MAID) is a primary immunodeficiency disease in which patients suffer from profound lymphopenia leading to recurrent infections. The disease is caused by a single point mutation leading to a R171W amino acid change in the protein moesin (moesinR171W). Moesin is a member of the ERM family of proteins, which reversibly link the cortical actin cytoskeleton to the plasma membrane. Here, we describe a novel mouse model with global expression of moesinR171W that recapitulates multiple facets of patient disease, including severe lymphopenia. Further analysis reveals that these mice have diminished numbers of thymocytes and bone marrow precursors. X-MAID mice also exhibit systemic inflammation that is ameliorated by elimination of mature lymphocytes through breeding to a Rag1-deficient background. The few T cells in the periphery of X-MAID mice are highly activated and have mostly lost moesinR171W expression. In contrast, single-positive (SP) thymocytes do not appear activated and retain high expression levels of moesinR171W. Analysis of ex vivo CD4 SP thymocytes reveals defects in chemotactic responses and reduced migration on integrin ligands. While chemokine signaling appears intact, CD4 SP thymocytes from X-MAID mice are unable to polarize and rearrange cytoskeletal elements. This mouse model will be a valuable tool for teasing apart the complexity of the immunodeficiency caused by moesinR171W, and will provide new insights into how the actin cortex regulates lymphocyte function.

LCP1 is a prognostic biomarker correlated with immune infiltrates in gastric cancer.

BACKGROUND: Previous studies have identified LCP1 as a diagnostic and prognostic marker in several cancers. However, the role of LCP1 in gastric cancer (GC) and its effect on tumor immune infiltration remain unclear. OBJECTIVE: The aim was to explore the role of LCP1 in GC and its effect on tumor immune infiltration. METHODS: We explored the expression of LCP1 relative to clinicopathology in GC patients by bioinformatics analysis and immunohistochemistry. Using cBioportal database, we analyzed the characteristic genetic variations of LCP1 in GC. In addition, we evaluated the correlation between LCP1 expression and tumor-infiltrating lymphocytes (TILs) using R software, TIMER and TISIDB databases. Finally, we analyzed the biological functions in which LCP1 may participate and the signaling pathways it may regulate. RESULTS: Here, we showed that LCP1 expression is significantly correlated with tumor aggressiveness and poor prognosis in GC patients. Additionally, the results indicated that LCP1 was associated with TILs, including both immunosuppressive and immunosupportive cells, and was strongly correlated with various immune marker sets in GC. GSEA analysis demonstrated that LCP1 expression played an important role in lymphocyte formation and immune reaction. CONCLUSIONS: LCP1 may be a potential prognostic biomarker for GC patients and a marker for tumor immunotherapy.

Altered glycosylation of IgG4 promotes lectin complement pathway activation in anti-PLA2R1-associated membranous nephropathy.

Primary membranous nephropathy (pMN) is a leading cause of nephrotic syndrome in adults. In most cases, this autoimmune kidney disease is associated with autoantibodies against the M-type phospholipase A2 receptor (PLA2R1) expressed on kidney podocytes, but the mechanisms leading to glomerular damage remain elusive. Here, we developed a cell culture model using human podocytes and found that anti-PLA2R1-positive pMN patient sera or isolated IgG4, but not IgG4-depleted sera, induced proteolysis of the 2 essential podocyte proteins synaptopodin and NEPH1 in the presence of complement, resulting in perturbations of the podocyte cytoskeleton. Specific blockade of the lectin pathway prevented degradation of synaptopodin and NEPH1. Anti-PLA2R1 IgG4 directly bound mannose-binding lectin in a glycosylation-dependent manner. In a cohort of pMN patients, we identified increased levels of galactose-deficient IgG4, which correlated with anti-PLA2R1 titers and podocyte damage induced by patient sera. Assembly of the terminal C5b-9 complement complex and activation of the complement receptors C3aR1 or C5aR1 were required to induce proteolysis of synaptopodin and NEPH1 by 2 distinct proteolytic pathways mediated by cysteine and aspartic proteinases, respectively. Together, these results demonstrated a mechanism by which aberrantly glycosylated IgG4 activated the lectin pathway and induced podocyte injury in primary membranous nephropathy.

Moesin is involved in microglial activation accompanying morphological changes and reorganization of the actin cytoskeleton.

Moesin is a member of the ezrin, radixin and moesin (ERM) proteins that are involved in the formation and/or maintenance of cortical actin organization through their cross-linking activity between actin filaments and proteins located on the plasma membranes as well as through regulation of small GTPase activities. Microglia, immune cells in the central nervous system, show dynamic reorganization of the actin cytoskeleton in their process elongation and retraction as well as phagocytosis and migration. In microglia, moesin is the predominant ERM protein. Here, we show that microglial activation after systemic lipopolysaccharide application is partly inhibited in moesin knockout (Msn-KO) mice. We prepared primary microglia from wild-type and Msn-KO mice, and studied them to compare their phenotypes accompanying morphological changes and reorganization of the actin cytoskeleton induced by UDP-stimulated phagocytosis and ADP-stimulated migration. The Msn-KO microglia showed higher phagocytotic activity in the absence of UDP, which was not further increased by the treatment with UDP. They also exhibited decreased ADP-stimulated migration activities compared with the wild-type microglia. However, the Msn-KO microglia retained their ability to secrete tumor necrosis factor α and nitric oxide in response to lipopolysaccharide.

The actin-bundling protein L-plastin-A double-edged sword: Beneficial for the immune response, maleficent in cancer.

The dynamic organization of the actin cytoskeleton into bundles and networks is orchestrated by a large variety of actin-binding proteins. Among them, the actin-bundling protein L-plastin is normally expressed in hematopoietic cells, where it is involved in the immune response. However, L-plastin is also often ectopically expressed in malignant cancer cells of non-hematopoietic origin and is even considered as a marker for cancer progression. Post-translational modification modulates L-plastin activity. In particular, L-plastin Ser5 phosphorylation has been shown to be important for the immune response in leukocytes as well as for invasion and metastasis formation of carcinoma cells. This chapter discusses the physiological and pathological role of L-plastin with a special focus on the importance of L-plastin Ser5 phosphorylation for the protein functions. The potential use of Ser5 phosphorylated L-plastin as a biomarker and/or therapeutic target will be evoked.

Preclinical Characterization of an Antibody-Drug Conjugate Targeting CS-1 and the Identification of Uncharacterized Populations of CS-1-Positive Cells.

Multiple myeloma is a hematologic cancer that disrupts normal bone marrow function and has multiple lines of therapeutic options, but is incurable as patients ultimately relapse. We developed a novel antibody-drug conjugate (ADC) targeting CS-1, a protein that is highly expressed on multiple myeloma tumor cells. The anti-CS-1 mAb specifically bound to cells expressing CS-1 and, when conjugated to a cytotoxic pyrrolobenzodiazepine payload, reduced the viability of multiple myeloma cell lines in vitro In mouse models of multiple myeloma, a single administration of the CS-1 ADC caused durable regressions in disseminated models and complete regression in a subcutaneous model. In an exploratory study in cynomolgus monkeys, the CS-1 ADC demonstrated a half-life of 3 to 6 days; however, no highest nonseverely toxic dose was achieved, as bone marrow toxicity was dose limiting. Bone marrow from dosed monkeys showed reductions in progenitor cells as compared with normal marrow. In vitro cell killing assays demonstrated that the CS-1 ADC substantially reduced the number of progenitor cells in healthy bone marrow, leading us to identify previously unreported CS-1 expression on a small population of progenitor cells in the myeloid-erythroid lineage. This finding suggests that bone marrow toxicity is the result of both on-target and off-target killing by the ADC.

Allograft inflammatory factor-1 in myeloid cells drives autoimmunity in type 1 diabetes.

Allograft inflammatory factor-1 (AIF1) is a calcium-responsive cytoplasmic scaffold protein that directs hematopoiesis and immune responses within dendritic cells (DC) and macrophages. Although the role of AIF1 in transplant rejection and rheumatoid arthritis has been explored, little is known about its role in type 1 diabetes. Here, we show that in vivo silencing of AIF1 in NOD mice restrained infiltration of immune cells into the pancreas and inhibited diabetes incidence. Analyses of FACS-sorted CD45neg nonleukocyte populations from resected pancreatic islets showed markedly higher expression of insulin in the AIF1-silenced groups. Evaluation of CD45+ leukocytes revealed diminished infiltration of effector T cells and DC in the absence of AIF1. Transcriptional profiling further revealed a marked decrease in cDC1 DC-associated genes CD103, BATF3, and IRF8, which are required for orchestrating polarized type 1 immunity. Reduced T cell numbers within the islets were observed, with concomitant lower levels of IFN-γ and T-bet in AIF1-silenced cohorts. In turn, there was a reciprocal increase in functionally suppressive pancreas-resident CD25+Foxp3+CD4+ Tregs. Taken together, results show that AIF1 expression in myeloid cells plays a pivotal role in promoting type 1 diabetes and that its suppression restrains insulitis by shifting the immune microenvironment toward tolerance.