Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America.
PLoS Pathog. 2013;9(6):e1003446. doi: 10.1371/journal.ppat.1003446. Epub 2013 Jun 27.
Phagocytosis of the opportunistic fungal pathogen Candida albicans by cells of the innate immune system is vital to prevent infection. Dectin-1 is the major phagocytic receptor involved in anti-fungal immunity. We identify two new interacting proteins of Dectin-1 in macrophages, Bruton's Tyrosine Kinase (BTK) and Vav1. BTK and Vav1 are recruited to phagocytic cups containing C. albicans yeasts or hyphae but are absent from mature phagosomes. BTK and Vav1 localize to cuff regions surrounding the hyphae, while Dectin-1 lines the full length of the phagosome. BTK and Vav1 colocalize with the lipid PI(3,4,5)P3 and F-actin at the phagocytic cup, but not with diacylglycerol (DAG) which marks more mature phagosomal membranes. Using a selective BTK inhibitor, we show that BTK contributes to DAG synthesis at the phagocytic cup and the subsequent recruitment of PKCε. BTK- or Vav1-deficient peritoneal macrophages display a defect in both zymosan and C. albicans phagocytosis. Bone marrow-derived macrophages that lack BTK or Vav1 show reduced uptake of C. albicans, comparable to Dectin1-deficient cells. BTK- or Vav1-deficient mice are more susceptible to systemic C. albicans infection than wild type mice. This work identifies an important role for BTK and Vav1 in immune responses against C. albicans.
先天免疫系统细胞吞噬机会性真菌病原体白念珠菌对于预防感染至关重要。Dectin-1 是参与抗真菌免疫的主要吞噬受体。我们在巨噬细胞中鉴定了 Dectin-1 的两个新的相互作用蛋白，Btk 和 Vav1。Btk 和 Vav1 被招募到含有白念珠菌酵母或菌丝的吞噬杯中，但不存在于成熟的吞噬体中。Btk 和 Vav1 定位于围绕菌丝的袖口区域，而 Dectin-1 则沿吞噬体的全长排列。Btk 和 Vav1 与脂质 PI(3,4,5)P3 和 F-肌动蛋白在吞噬杯中共定位，但与标志更成熟吞噬体膜的二酰基甘油 (DAG) 不同。使用选择性 Btk 抑制剂，我们表明 Btk 有助于吞噬杯中 DAG 的合成以及随后 PKCε 的募集。缺乏 Btk 或 Vav1 的腹膜巨噬细胞在几丁质和白念珠菌吞噬作用中均存在缺陷。缺乏 Btk 或 Vav1 的骨髓来源巨噬细胞对白色念珠菌的摄取减少，与 Dectin1 缺陷细胞相当。缺乏 Btk 或 Vav1 的小鼠比野生型小鼠更容易发生系统性白色念珠菌感染。这项工作确定了 Btk 和 Vav1 在针对白色念珠菌的免疫反应中的重要作用。
