Blanco-Menéndez Noelia, Del Fresno Carlos, Fernandes Sandra, Calvo Enrique, Conde-Garrosa Ruth, Kerr William G, Sancho David
Centro Nacional de Investigaciones Cardiovasculares "Carlos III" (CNIC), Melchor Fernández Almagro 3, Madrid, 28029, Spain.
Microbiology and Immunology Department, SUNY Upstate Medical University, Syracuse, New York, USA.
J Immunol. 2015 Nov 1;195(9):4466-4478. doi: 10.4049/jimmunol.1402874. Epub 2015 Sep 28.
Dectin-1 (Clec7a) is a paradigmatic C-type lectin receptor that binds Syk through a hemITAM motif and couples sensing of pathogens such as fungi to induction of innate responses. Dectin-1 engagement triggers a plethora of activating events, but little is known about the modulation of such pathways. Trying to define a more precise picture of early Dectin-1 signaling, we explored the interactome of the intracellular tail of the receptor in mouse dendritic cells. We found unexpected binding of SHIP-1 phosphatase to the phosphorylated hemITAM. SHIP-1 colocalized with Dectin-1 during phagocytosis of zymosan in a hemITAM-dependent fashion. Moreover, endogenous SHIP-1 relocated to live or heat-killed Candida albicans-containing phagosomes in a Dectin-1-dependent manner in GM-CSF-derived bone marrow cells (GM-BM). However, SHIP-1 absence in GM-BM did not affect activation of MAPK or production of cytokines and readouts dependent on NF-κB and NFAT. Notably, ROS production was enhanced in SHIP-1-deficient GM-BM treated with heat-killed C. albicans, live C. albicans, or the specific Dectin-1 agonists curdlan or whole glucan particles. This increased oxidative burst was dependent on Dectin-1, Syk, PI3K, phosphoinositide-dependent protein kinase 1, and NADPH oxidase. GM-BM from CD11c∆SHIP-1 mice also showed increased killing activity against live C. albicans that was dependent on Dectin-1, Syk, and NADPH oxidase. These results illustrate the complexity of myeloid C-type lectin receptor signaling, and how an activating hemITAM can also couple to intracellular inositol phosphatases to modulate selected functional responses and tightly regulate processes such as ROS production that could be deleterious to the host.
脱噬素-1（Clec7a）是一种典型的C型凝集素受体，它通过一个半免疫受体酪氨酸激活基序（hemITAM）与脾酪氨酸激酶（Syk）结合，并将对真菌等病原体的感知与先天免疫反应的诱导相偶联。脱噬素-1的结合会引发大量激活事件，但对这些信号通路的调节却知之甚少。为了更精确地描绘脱噬素-1早期信号传导的情况，我们探索了小鼠树突状细胞中该受体细胞内尾部的相互作用组。我们发现SHIP-1磷酸酶与磷酸化的hemITAM意外结合。在酵母聚糖吞噬过程中，SHIP-1以hemITAM依赖的方式与脱噬素-1共定位。此外，在内源性粒细胞-巨噬细胞集落刺激因子（GM-CSF）衍生的骨髓细胞（GM-BM）中，内源性SHIP-1以脱噬素-1依赖的方式重新定位到含有活的或热灭活白色念珠菌的吞噬体中。然而，GM-BM中SHIP-1的缺失并不影响丝裂原活化蛋白激酶（MAPK）的激活或细胞因子的产生以及依赖于核因子κB（NF-κB）和活化T细胞核因子（NFAT）的检测指标。值得注意的是，在用热灭活白色念珠菌、活的白色念珠菌或脱噬素-1特异性激动剂可德胶或全葡聚糖颗粒处理的SHIP-1缺陷型GM-BM中，活性氧（ROS）的产生增强。这种增加的氧化爆发依赖于脱噬素-1、Syk、磷脂酰肌醇-3激酶（PI3K）、磷酸肌醇依赖性蛋白激酶1和烟酰胺腺嘌呤二核苷酸磷酸氧化酶（NADPH氧化酶）。来自CD11c∆SHIP-1小鼠的GM-BM对活的白色念珠菌的杀伤活性也增加，这依赖于脱噬素-1、Syk和NADPH氧化酶。这些结果说明了髓系C型凝集素受体信号传导的复杂性，以及一个激活的hemITAM如何也能与细胞内肌醇磷酸酶偶联，以调节特定的功能反应，并严格调控可能对宿主有害的过程，如ROS的产生。
