Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity

Groß, Olaf; Gewies, Andreas; Finger, Katrin; Schäfer, Martin; Sparwasser, Tim; Peschel, Christian; Förster, Irmgard; Ruland, Jürgen

doi:10.1038/nature04926

Cited by 761 publications

(887 citation statements)

References 30 publications

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“…The transcription factor NF-kB is a major regulator of proinflammatory cytokines that acts downstream of Dectin-1 via the activation of CARD9 [3,13,14]. To assess the role of PLCg2 in Dectin-1-induced NF-kB activation, first we measured the sitespecific phosphorylation (ser 536) of the p65 NF-kB subunit in DC lacking PLCg2.…”

Section: Dectin-1 Requires Plcc2 For Ap-1 Nf-jb and Nfat Activationmentioning

confidence: 99%

“…Upon ligand binding, this motif is phosphorylated by src family kinases [8] and recruits the tyrosine kinase Syk [9], which initiates a signaling cascade leading to NF-kB [10], NFAT [11] and MAPK [12] activation. Along with Bcl-10 and MALT1, CARD9 is a crucial mediator in the ITAM-signaling pathway that links recognition of b-glucan by Dectin-1 to NF-kB and MAPK activation [13,14]. Overall, the Syk-CARD9 pathway is essential for promoting Dectin-1-mediated DC responses to fungal infection [15][16][17], in particular the induction of DC maturation and secretion of IL-23, which sustains and amplifies T H 17 CD4 1 T H cell differentiation [18].…”

Section: Introductionmentioning

confidence: 99%

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Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

et al. 2009

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DC recognize microbial components through an array of receptors known as PRR. PRR initiate intracellular signals, which engender DC with the capacity to stimulate T-cell responses. Dectin-1 is a PRR that recognizes b-glucan, a major constituent of many fungi's outer cell wall. Here we show that Dectin-1 activates DC through phospholipase (PLC)c2 signaling. PLCc2-deficient DC were unable to expand antigen-specific T cells and induce T H 1 and T H 17 differentiation in response to b-glucan. Mechanistically, PLCc2-deficiency impaired the capacity of DC to secrete polarizing cytokines following exposure to b-glucan. Dectin-1 required PLCc2 to activate MAPK, AP-1 and NF-jB, which induce cytokine gene expression. Moreover, PLCc2 controlled Dectin-1-mediated NFAT activation and induction of NFAT-dependent genes such as IL-2, cyclooxigenase-2 and Egr transcription factors. We conclude that PLCc2 is a crucial signaling mediator that modifies DC gene expression program to activate DC responses to b-glucan-containing pathogens.Key words: DC . Dectin-1 . PLCg . Signaling Supporting Information available online Introduction DC play a key role in gathering information from the surrounding environment and initiating appropriate immune responses when needed [1,2]. Because they bridge innate and adaptive immunity, DC are equipped with a multitude of intracellular and cell surface receptors that sense microbial components and trigger host responses to invading pathogens. These receptors, collectively known as PRR, include TLR [3], C-type lectins such as Dectin-1 [4], scavenger receptors [5], the nucleotide-binding oligomerization domain (NOD) proteins NOD1 and NOD2, the NOD-like receptors and the RIG-like receptors [6].Dectin-1 recognizes b-glucan, a major constituent of many fungi's outer cell wall [4,7] and triggers intracellular signals through a cytoplasmic tyrosine motif resembling the ITAM. Upon ligand binding, this motif is phosphorylated by src family kinases [8] and recruits the tyrosine kinase Syk [9], which initiates a signaling cascade leading to NF-kB [10], NFAT [11] and MAPK [12] activation. Along with Bcl-10 and MALT1, CARD9 is a crucial mediator in the ITAM-signaling pathway that links recognition of b-glucan by Dectin-1 to NF-kB and MAPK activation [13,14]. Overall, the Syk-CARD9 pathway is essential for [20,21]. Syk, together with the tyrosine kinases BTK and Src, activate PLCg through tyrosine phosphorylation [22]. Another downstream ITAM mediator, PI-3K, activates PLCg by generating phosphatidylinositol 3,4,5 trisphosphate, which binds the pleckstrin homology domain of PLCg, promoting PLCg recruitment to the cell membrane. Thus, the ability of Dectin-1 to initiate an ITAM-Syk-signaling pathway [9] provides a rationale for studying the role of PLCg in Dectin-1-mediated antimicrobial responses in DC.PLCg includes two isoforms, PLCg1 and PLCg2, which hydrolyze membrane phosphatidylinositol 4,5-biphosphate into inositol 1,4,5-trisphosphate and diacylglicerol (DAG) [20]. Inositol 1,4,5-trisphosphate triggers the ...

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Section: Dectin-1 Requires Plcc2 For Ap-1 Nf-jb and Nfat Activationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

et al. 2009

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“…Ligand binding results in phosphorylation of the ITAM motif, leading to the activation of the downstream tyrosine kinase Syk, CARD9 and initiation of phagocytosis, respiratory burst and production of the cytokines IL-2 and IL-10 [25,26].…”

Section: Introductionmentioning

confidence: 99%

CD8^– dendritic cells preferentially cross‐present Saccharomyces cerevisiae antigens

et al. 2008

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Mouse splenic dendritic cell (DC) subsets possess distinct antigen-presentation abilities. CD8 + DC are specialized in cross-presentation of antigens to CD8 + T cells, whereas CD8 -DC are more efficient in antigen presentation to CD4 + T cells. In this study, we examined the capacity of CD8 + and CD8 -DC subsets to present fungal antigens in MHC class I and II molecules to CD8 + and CD4 + T cells, respectively. We used ovalbuminexpressing Saccharomyces cerevisiae (yeast-OVA) as a fungal model system. Both CD8 + and CD8 -DC subsets phagocytosed yeast in equal amounts and uptake was mediated via dectin-1. In addition, both DC subsets induced similar OVA-specific CD4 + T cell proliferation after incubation with yeast-OVA. However, the induction of OVA-specific CD8 + T cell activation was largely restricted to the CD8 -DC subset. Furthermore, only CD8 -DC produced cytokines such as IL-10 and TNF-a and increased IL-23p19 and IL-23p40 mRNA levels in response to yeast. Our results strongly suggest that DC subsets have different functions in the elicitation of adaptive immune responses in vivo. IntroductionFungal infections with pathogenic yeasts such as Candida albicans, Aspergillus fumigatus, Histoplasma capsulatum and Cryptococcus neoformans are a major problem in immunocompromised persons. These opportunistic pathogens usually do not pose problems in healthy individuals, but frequently become invasive in patients suffering from HIV, patients with malignancies or transplant recipients, resulting in life-threatening diseases [1][2][3].Both innate and adaptive immune responses are essential to induce protection against fungi. Dendritic cells (DC) play a central role in the adaptive immune response by capturing fungi and presenting their antigens in major histocompatibility complex (MHC) class I and MHC class II molecules to T cells [4, 5]. DC express a panel of microbial recognition receptors such as Toll-like receptors (TLR) and C-type lectin receptors that are essential for the elicitation of adaptive immune responses [6]. Of these receptors, TLR2 and the DCassociated C-type lectin (dectin-1) are specifically involved in recognition of fungal components [7][8][9]. Zymosan and fungal pathogens like C. albicans and A. fumigatus are sensed by TLR2 that signals via myeloid differentiation factor 88 (MyD88), resulting in NF-jB activation and the production of cytokines [10][11][12][13]. The importance of this signaling cascade can be inferred from the fact that MyD88-knockout mice show an increased susceptibility to fungal infections [14,15].Dectin-1 is expressed on myeloid cells like macrophages, neutrophils, monocytes, and even a subset of T cells [16]. Dectin-1 mediates fungal recognition and Revised 2/11/07 Accepted 11/12/07 [DOI 10.1002/eji.200737647] Key words: Antigen presentation Á Dendritic cell Á Fungal Á T cell Abbreviations: b2m: b2-microglobulin Á Dectin-1: DC-associated C-type lectin-1 Á CR3: complement receptor 3 Á MR: mannose receptor Á SIGNR1: ICAM-3-grabbing nonintegrin (DC-SIGN) homolog, SIGN-related...

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“…In those cells, Dectin-1 acts primarily in synergy with other innate immune receptors such as toll-like receptors (TLRs) [10,11]. Notably, both Dectin-1 and CARD9 are important for resistance to fungal infection in both mice [7,12,13] and humans [14,15], indicating the importance of the CLR/Syk signaling pathway in immunity.The features of Dectin-1, including type II membrane topology, single Dectin-1-like C-type lectin-like domain and intracellular hemITAM are shared by two other CLRs, DNGR-1 (CLEC9A) and CLEC-2 (CLEC1B). DNGR-1 is selectively expressed by DCs and acts as a receptor for dead cells, facilitating cross-priming to cell-associated antigens [16].…”

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confidence: 99%

CLEC‐2 signaling via Syk in myeloid cells can regulate inflammatory responses

et al. 2011

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Myeloid cells express a plethora of C-type lectin receptors (CLRs) that can regulate immune responses. CLEC-2 belongs to the Dectin-1 sub-family of CLRs that possess an extracellular C-type lectin-like domain and a single intracellular hemITAM motif. CLEC-2 is highly expressed on mouse and human platelets where it signals via Syk to promote aggregation. We generated a monoclonal antibody (mAb) against mouse CLEC-2 and found that CLEC-2 is additionally widely expressed on leukocytes and that its expression is upregulated during inflammation. MAb-mediated crosslinking of CLEC-2 leads to hemI-TAM-dependent signaling via Syk, Ca 21 and NFAT and, in myeloid cells, modulates the effect of toll-like receptor (TLR) agonists to selectively potentiate production of IL-10. A macrophage/dendritic cell-dependent increase in IL-10 is also observed in mice given anti-CLEC-2 mAb together with LPS. Collectively, these data indicate that CLEC-2 is expressed in myeloid cells and acts as a Syk-coupled CLR able to modulate TLR signaling and inflammatory responses.Key words: CLEC-2 . C-type lectin . HemITAM . IL-10 . Syk Supporting Information available online IntroductionSignaling by some members of the C-type lectin receptor (CLR) superfamily plays a key role in innate immunity and in regulation of myeloid cell function [1,2]. A classical example is Dectin-1, which is expressed by macrophages (MØs), neutrophils and dendritic cells (DCs) and acts as a pattern recognition receptor for b-glucans present on fungal and some bacterial cell walls. Dectin-1 signals via a phospho-tyrosine-based hemITAM motif in its intracellular domain that recruits spleen tyrosine kinase (Syk) [3,4]. Dectin-1 signaling through Syk in myeloid cells can variably lead to phagocytosis, production of reactive oxygen species (ROS) and/or induction of innate response genes, including those encoding pro-inflammatory cytokines [5,6]. 3040Pro-inflammatory Dectin-1 signaling requires CARD9-dependent activation of NF-kB [7] although Dectin-1 can also signal to NF-kB via a Syk-independent pathway [8]. Although many DC types are potently activated by Dectin-1 agonists, in other myeloid cells Dectin-1 signaling only weakly activates the proinflammatory gene program [9]. In those cells, Dectin-1 acts primarily in synergy with other innate immune receptors such as toll-like receptors (TLRs) [10,11]. Notably, both Dectin-1 and CARD9 are important for resistance to fungal infection in both mice [7,12,13] and humans [14,15], indicating the importance of the CLR/Syk signaling pathway in immunity.The features of Dectin-1, including type II membrane topology, single Dectin-1-like C-type lectin-like domain and intracellular hemITAM are shared by two other CLRs, DNGR-1 (CLEC9A) and CLEC-2 (CLEC1B). DNGR-1 is selectively expressed by DCs and acts as a receptor for dead cells, facilitating cross-priming to cell-associated antigens [16]. CLEC-2 was first identified in a screen for natural killer (NK) cell receptors and its mRNA was found in myeloid cells and in some NK-cell clones [...

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Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity

Cited by 761 publications

References 30 publications

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

CD8^– dendritic cells preferentially cross‐present Saccharomyces cerevisiae antigens

CLEC‐2 signaling via Syk in myeloid cells can regulate inflammatory responses

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Card9 controls a non-TLR signalling pathway for innate anti-fungal immunity

Cited by 761 publications

References 30 publications

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of TH1/TH17 polarization

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of TH1/TH17 polarization

CD8– dendritic cells preferentially cross‐present Saccharomyces cerevisiae antigens

CLEC‐2 signaling via Syk in myeloid cells can regulate inflammatory responses

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Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

Requirement of phospholipase C‐γ2 (PLCγ2) for Dectin‐1‐induced antigen presentation and induction of T_H1/T_H17 polarization

CD8^– dendritic cells preferentially cross‐present Saccharomyces cerevisiae antigens