Binding of a C-type lectin’s coiled-coil domain to the Domeless receptor directly activates the JAK/STAT pathway in the shrimp immune response to bacterial infection

Abstract

C-type lectins (CTLs) are characterized by the presence of a C-type carbohydrate recognition domain (CTLD) that by recognizing microbial glycans, is responsible for their roles as pattern recognition receptors in the immune response to bacterial infection. In addition to the CTLD, however, some CTLs display additional domains that can carry out effector functions, such as the collagenous domain of the mannose-binding lectin. While in vertebrates, the mechanisms involved in these effector functions have been characterized in considerable detail, in invertebrates they remain poorly understood. In this study, we identified in the kuruma shrimp (Marsupenaeus japonicus) a structurally novel CTL (MjCC-CL) that in addition to the canonical CTLD, contains a coiled-coil domain (CCD) responsible for the effector functions that are key to the shrimp's antibacterial response mediated by antimicrobial peptides (AMPs). By the use of in vitro and in vivo experimental approaches we elucidated the mechanism by which the recognition of bacterial glycans by the CTLD of MjCC-CL leads to activation of the JAK/STAT pathway via interaction of the CCD with the surface receptor Domeless, and upregulation of AMP expression. Thus, our study of the shrimp MjCC-CL revealed a striking functional difference with vertebrates, in which the JAK/STAT pathway is indirectly activated by cell death and stress signals through cytokines or growth factors. Instead, by cross-linking microbial pathogens with the cell surface receptor Domeless, a lectin directly activates the JAK/STAT pathway, which plays a central role in the shrimp antibacterial immune responses by upregulating expression of selected AMPs. Funding: This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 31630084, 31130056 and 31472303). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Author summaryThe JAK/STAT pathway mediates the effects of a large number of cytokines and growth factors. It is activated following binding of a cytokine or growth factor to its respective receptor. To date, over 50 cytokines and growth factors have been shown to utilize the pathway to regulate cell growth, survival differentiation, motility, and immune responses. The JAK/ STAT pathway is ubiquitous in vertebrates but can also be found as an intact pathway in some invertebrates, including shrimp. However, few cytokines and growth factors like molecules are identified in invertebrates and the function of the pathway in invertebrates is seldom studied. In this study, we identified core components of JAK/STAT pathway in shrimp and found the pathway had an important function in antibacterial immunity. Bacterial pathogens directly activate the JAK/STAT pathway through a secreted C-type lectin containing a coiled coil domain and a C-type lectin domain (MjCC-CL) in shrimp. Working as a cytokine like ligand, the MjCC-CL binds to polysaccharides from bacteria and the ILR domain of Domeles...

RNAi screening identifies a new Toll from shrimp Litopenaeus vannamei that restricts WSSV infection through activating Dorsal to induce antimicrobial peptides

“…Fluorescence was visualized on a confocal laser scanning microscope (Leica TCS-SP5, Germany). We calculated the colocalization percentage of Dorsal with nucleus stained with hochest, using the ImageJ according to the previously described methods [ 51 , 102 ]. In brief, we opened the picture and chosen Image-Color-Split channels, while closed the no need channels, and then clicked Plugins-colocalization analysis-colocalization threshold-OK.…”

Protein Inhibitor of Activated STAT (PIAS) Negatively Regulates the JAK/STAT Pathway by Inhibiting STAT Phosphorylation and Translocation

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