Signalling through MyD88 drives surface expression of the mycobacterial receptors MCL (Clecsf8, Clec4d) and Mincle (Clec4e) following microbial stimulation

Kerscher, Bernhard; Dambuza, Ivy M.; Christofi, Maria; Reid, Delyth M.; Yamasaki, Sho; Willment, Janet A.; Brown, Gordon D.

doi:10.1016/j.micinf.2016.03.007

Cited by 27 publications

(27 citation statements)

References 25 publications

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“…7). First, we observed that the TLR2-driven induction of Mincle surface expression is operative and consistent with data from previous reports on TLR4 action (37,40), MyD88-dependent upregulation in response to Mycobacterium bovis BCG (42), and TLR2 activity (43). This C/EBP␤-dependent feed-forward loop enhancing the response to Mincle ligands (37) most likely accounts for the TLR2-driven G-CSF production in response to cell wall glycolipid challenge, although we acknowledge that formal proof of this mechanism would require the demonstration that the overexpression of Mincle, perhaps in association with other CLRs like Mcl, circumvents TLR2 dependence.…”

Section: Discussionsupporting

confidence: 91%

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids

et al. 2017

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Nontoxigenic Corynebacterium diphtheriae and Corynebacterium ulcerans cause invasive disease in humans and animals. Host sensing of corynebacteria is largely uncharacterized, albeit the recognition of lipoglycans by Toll-like receptor 2 (TLR2) appears to be important for macrophage activation by corynebacteria. The members of the order Corynebacterineae (e.g., mycobacteria, nocardia, and rhodococci) share a glycolipid-rich cell wall dominated by mycolic acids (termed corynomycolic acids in corynebacteria). The mycolic acid-containing cord factor of mycobacteria, trehalose dimycolate, activates the C-type lectin receptor (CLR) Mincle. Here, we show that glycolipid extracts from the cell walls of several pathogenic and nonpathogenic Corynebacterium strains directly bound to recombinant Mincle in vitro. Macrophages deficient in Mincle or its adapter protein Fc receptor gamma chain (FcR␥) produced severely reduced amounts of granulocyte colony-stimulating factor (G-CSF) and of nitric oxide (NO) upon challenge with corynebacterial glycolipids. Consistently, cell wall extracts of a particular C. diphtheriae strain (DSM43989) lacking mycolic acid esters neither bound Mincle nor activated macrophages. Furthermore, TLR2 but not TLR4 was critical for sensing of cell wall extracts and whole corynebacteria. The upregulation of Mincle expression upon encountering corynebacteria required TLR2. Thus, macrophage activation by the corynebacterial cell wall relies on TLR2-driven robust Mincle expression and the cooperative action of both receptors.KEYWORDS C-type lectin receptor, Mincle, Toll-like receptor, macrophage, Corynebacterium diphtheriae, cell wall lipids, mycolate, mycolic acid, corynomycolate D iphtheria caused by toxin-producing Corynebacterium diphtheriae is a severe, life-threatening infection, which has become rare in Europe due to the efficacy and coverage of toxoid immunization but still causes a considerable burden of disease globally. Corynebacterium ulcerans and Corynebacterium pseudotuberculosis can also harbor the tox gene encoding diphtheria toxin (1) and in addition may secrete the exotoxin phospholipase D, a virulence factor involved in caseous lymphadenitis of sheep and goats (2, 3). Rates of infections with nontoxigenic strains of C. diphtheriae, including bloodstream infections and endocarditis, appear to be increasing in Europe (4,5). Of the 90 species that comprise the genus Corynebacterium, many inhabit the human skin or mucosa as commensals (6), with C. striatum, C. tuberculostearicum, C. amycolatum, and C. jeikeium being typical examples of skin inhabitants, whereas C. urealyticum and C. glucuronolyticum are frequently found in the urogenital tract. All

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Section: Discussionsupporting

confidence: 91%

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids

et al. 2017

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“…MyD88 is a key adaptor protein which is common to all TLRs except TLR3 [39]. The interaction between TLR and MyD88 is required for signaling via the MAPK/NF-κB pathways [16,40]. Consistent with the requirement of this adaptor protein for TLR response, we show that MyD88 -/-THP-1 cells did not produce MMP-9 following stimulation with Pam3CSK4.…”

Section: Discussionsupporting

confidence: 74%

Pam3CSK4 Induces MMP-9 Expression in Human Monocytic THP-1 Cells

Al-Rashed

Kochumon

Usmani

et al. 2017

Cell Physiol Biochem

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Background: Matrix metalloproteinase (MMP)-9 is known to degrade the extracellular matrix and increased MMP-9 levels are related with the pathogenesis of many inflammatory conditions including obesity. Pam3CSK4 is a synthetic triacylated lipopeptide (LP) which is a potent activator of immune cells and induces cytokine production. However, it is unclear whether Pam3CSK4 is able to induce MMP-9 expression in monocytic cells. We, therefore, determined MMP-9 production by Pam3CSK4-treated THP-1 cells and also investigated the signal transduction pathway(s) involved. Methods: MMP-9 expression was determined by real-time qPCR and ELISA. MMP-9 activity was assessed by zymography. THP-1 cells, THP1-XBlue™ cells, THP1-XBlue™-defMyD cells, anti-TLR2 mAb and selective pharmacological inhibitors were used to study signaling pathways involved. Phosphorylated and total proteins were detected by western blotting. Results: Pam3CSK4 induced MMP-9 expression (P<0.05) at both mRNA and protein levels in human monocytic THP-1 cells. Increased NF-κB/AP-1 activity was detected in Pam3CSK4-treated THP-1 cells and MMP-9 production in these cells was significantly suppressed by pre-treatment with anti-TLR2 neutralizing antibody or by inhibition of clathrin-dependent endocytosis. Also, MyD88-/-THP-1 cells did not express MMP-9 following treatment with Pam3CSK4. Inhibition of JNK, MEK/ERK, p38 MAPK and NF-κB significantly suppressed MMP-9 gene expression (P<0.05). Conclusion: Pam3CSK4 induces MMP-9 production in THP-1 cells through the TLR-2/MyD88-dependent mechanism involving MEK/ERK, JNK, p38 MAPK and NF-κB/AP-1 activation.

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“…These data are in accordance with previous studies 5,6,16 and suggest that CLEC-1 requires other adaptor chains, other PRRs, or sufficient glycosylation for efficient expression, transport, and cell-surface stability as described for other CLRs. 17,18 No improvement was observed by cotransfecting cells with plasmids encoding the adaptor proteins DAP12 and FcRg (data not shown). Cell-surface CLEC-1 expression was confirmed by IHC in transfected cells with antihCLEC-1 mAb (D6 clone) (supplemental Figure 5B).…”

Section: Resultsmentioning

confidence: 95%

Cell-surface C-type lectin-like receptor CLEC-1 dampens dendritic cell activation and downstream Th17 responses

et al. 2017

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Key Points• CLEC-1 is restricted to CD16 2 myeloid DCs in human blood and acts as an inhibitory receptor to restrain downstream Th17 activation.• CLEC-1-deficient rats highlight an in vivo function for CLEC-1 in preventing excessive T-cell priming and effector Th responses.Dendritic cells (DCs) represent essential antigen-presenting cells that are critical for linking innate and adaptive immunity, and influencing T-cell responses. Among pattern recognition receptors, DCs express C-type lectin receptors triggered by both exogenous and endogenous ligands, therefore dictating pathogen response, and also shaping T-cell immunity.We previously described in rat, the expression of the orphan C-type lectin-like receptor-1 (CLEC- 1) by DCs and demonstrated in vitro its inhibitory role in downstream T helper 17 (Th17)activation. In this study, we examined the expression and functionality of CLEC-1 in human DCs, and show a cell-surface expression on the CD16 2 subpopulation of blood DCs and on monocytederived DCs (moDCs). CLEC-1 expression on moDCs is downregulated by inflammatory stimuli and enhanced by transforming growth factor b. Moreover, we demonstrate that CLEC-1 is a functional receptor on human moDCs and that although not modulating the spleen tyrosine kinase-dependent canonical nuclear factor-kB pathway, represses subsequent Th17 responses.Interestingly, a decreased expression of CLEC1A in human lung transplants is predictive of the development of chronic rejection and is associated with a higher level of interleukin 17A (IL17A). Importantly, using CLEC-1-deficient rats, we showed that disruption of CLEC-1 signaling led to an enhanced Il12p40 subunit expression in DCs, and to an exacerbation of downstream in vitro and in vivo CD4 1 Th1 and Th17 responses. Collectively, our results establish a role for CLEC-1 as an inhibitory receptor in DCs able to dampen activation and downstream effector Th responses. As a cell-surface receptor, CLEC-1 may represent a useful therapeutic target for modulating T-cell immune responses in a clinical setting.

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Signalling through MyD88 drives surface expression of the mycobacterial receptors MCL (Clecsf8, Clec4d) and Mincle (Clec4e) following microbial stimulation

Cited by 27 publications

References 25 publications

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids

Pam3CSK4 Induces MMP-9 Expression in Human Monocytic THP-1 Cells

Cell-surface C-type lectin-like receptor CLEC-1 dampens dendritic cell activation and downstream Th17 responses

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