The Weibel-Palade Body Localized SNARE (Soluble NSF Attachment Protein Receptor) Syntaxin-3 Modulates Von Willebrand Factor Secretion From Endothelial Cells

Objective Endothelial cells store von Willebrand factor (VWF) in rod-shaped secretory organelles, called Weibel-Palade bodies (WPBs). WPB exocytosis is coordinated by a complex network of Rab GTPases, Rab-effectors and SNARE proteins. We have previously identified STXBP1 as the link between the Rab27A-Slp4-a complex on WPBs and the SNARE proteins syntaxin-2 and -3. In this study we investigate the function of syntaxin-3 in VWF secretion. Approach and Results In human umbilical vein endothelial cells (HUVECs) and in blood outgrowth endothelial cells (BOECs) from healthy controls endogenous syntaxin-3 immunolocalized to WPBs. A detailed analysis of BOECs isolated from a patient with variant microvillus inclusion disease (MVID), carrying a homozygous mutation in STX3 (STX3-/-), showed a loss of syntaxin-3 protein and absence of WPB-associated syntaxin-3 immunoreactivity. Ultrastructural analysis revealed no detectable differences in morphology or prevalence of immature or mature WPBs in control versus STX3-/- BOECs. VWF multimer analysis showed normal patterns in plasma of the MVID patient, and media from STX3-/- BOECs, together indicating WPB formation and maturation are unaffected by absence of syntaxin-3. However, a defect in basal as well as Ca2+ - and cAMP-mediated VWF secretion was found in the STX3-/- BOECs. We also show that syntaxin-3 interacts with the WPB-associated SNARE protein VAMP8. Conclusions Our data reveal syntaxin-3 as a novel WPB-associated SNARE protein that controls WPB exocytosis

Alternative trafficking of Weibel-Palade body proteins in CRISPR/Cas9-engineered von Willebrand factor-deficient blood outgrowth endothelial cells

Background: Synthesis of the hemostatic protein von Willebrand factor (VWF) drives formation of endothelial storage organelles called Weibel‐Palade bodies (WPBs). In the absence of VWF, angiogenic and inflammatory mediators that are costored in WPBs are subject to alternative trafficking routes. In patients with von Willebrand disease (VWD), partial or complete absence of VWF/WPBs may lead to additional bleeding complications, such as angiodysplasia. Studies addressing the role of VWF using VWD patient–derived blood outgrowth endothelial cells (BOECs) have reported conflicting results due to the intrinsic heterogeneity of patient‐derived BOECs. Objective: To generate a VWF‐deficient endothelial cell model using clustered regularly interspaced short palindromic repeats (CRISPR) genome engineering of blood outgrowth endothelial cells. Methods: We used CRISPR/CRISPR‐associated protein 9 editing in single‐donor cord blood–derived BOECs (cbBOECs) to generate clonal VWF−/− cbBOECs. Clones were selected using high‐throughput screening, VWF mutations were validated by sequencing, and cells were phenotypically characterized. Results: Two VWF−/− BOEC clones were obtained and were entirely devoid of WPBs, while their overall cell morphology was unaltered. Several WPB proteins, including CD63, syntaxin‐3 and the cargo proteins angiopoietin (Ang)‐2, interleukin (IL)‐6, and IL‐8 showed alternative trafficking and secretion in the absence of VWF. Interestingly, Ang‐2 was relocated to the cell periphery and colocalized with Tie‐2. Conclusions: CRISPR editing of VWF provides a robust method to create VWF‐ deficient BOECs that can be directly compared to their wild‐type counterparts. Results obtained with our model system confirmed alternative trafficking of several WPB proteins in the absence of VWF and support the theory that increased Ang‐2/Tie‐2 interaction contributes to angiogenic abnormalities in VWD patients

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer‐reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state‐of‐the‐art handbook for basic and clinical researchers.DFG, 389687267, Kompartimentalisierung, Aufrechterhaltung und Reaktivierung humaner Gedächtnis-T-Lymphozyten aus Knochenmark und peripherem BlutDFG, 80750187, SFB 841: Leberentzündungen: Infektion, Immunregulation und KonsequenzenEC/H2020/800924/EU/International Cancer Research Fellowships - 2/iCARE-2DFG, 252623821, Die Rolle von follikulären T-Helferzellen in T-Helferzell-Differenzierung, Funktion und PlastizitätDFG, 390873048, EXC 2151: ImmunoSensation2 - the immune sensory syste

Differential effects of PD-1 and CTLA-4 blockade on the melanoma-reactive CD8 T cell response

Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) have revolutionized the treatment of melanoma patients. Based on early studies addressing the mechanism of action, it was assumed that PD-1 blockade mostly influences T cell responses at the tumor site. However, recent work has demonstrated that PD-1 blockade can influence the T cell compartment in peripheral blood. If the activation of circulating, tumor-reactive T cells would form an important mechanism of action of PD-1 blockade, it may be predicted that such blockade would alter either the frequency and/or the breadth of the tumor-reactive CD8 T cell response. To address this question, we analyzed CD8 T cell responses toward 71 melanoma-associated epitopes in peripheral blood of 24 melanoma patients. We show that both the frequency and the breadth of the circulating melanoma-reactive CD8 T cell response was unaltered upon PD-1 blockade. In contrast, a broadening of the circulating melanoma-reactive CD8 T cell response was observed upon CTLA-4 blockade, in concordance with our prior data. Based on these results, we conclude that PD-1 and CTLA-4 blockade have distinct mechanisms of action. In addition, the data provide an argument in favor of the hypothesis that anti-PD-1 therapy may primarily act at the tumor site

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion