期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：35
页码：15583-15588
DOI：10.1073/pnas.1010145107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：To kill macrophages, the lethal factor component of Bacillus anthracis toxin binds to a carrier protein (PA), which then interacts with the CMG2 receptor protein on the cell surface and is endocytosed into the cytoplasm. CMG2, as well as TEM8, a second PA receptor not present on macrophages, contain a von Willebrand A domain that is crucial for toxin binding. Here we report that integrin {beta}1, another cell surface von Willebrand A domain protein, can mediate and potentiate anthrax toxin endocytosis. By using microarray-based analysis to globally correlate gene expression profiles with toxin sensitivity, we associated toxin effects with the integrin-activating proteins osteopontin and CD44. Further study showed that PA binds to {alpha}4{beta}1- and {alpha}5{beta}1-integrin complexes, leading to their conjoint endocytosis, and also interacts--weakly relative to CMG2 but comparably to TEM8--with purified {alpha}5{beta}1 complex in vitro. Monoclonal antibody directed against {beta}1-integrin or its {alpha} integrin partners reduced PA/integrin endocytosis and anthrax toxin lethality, and hyaluronic acid--which interferes with CD44-mediated integrin activation--had similar effects. Remarkably, whereas deficiency of CMG2 protected macrophages from rapid killing by large toxin doses (>50 ng/mL), by 24 h the toxin-treated cells were dead. Such late killing of CMG2-deficient cells by high dose toxin as well as the late death observed during exposure of CMG2-producing macrophages to low-dose toxin (<1 ng/mL), was dependent on integrin function. Effects of inactivating both CMG2 and integrin were synergistic. Collectively, our findings argue strongly that {beta}1-integrin can both potentiate CMG2-mediated endocytosis and serve independently as a low-affinity PA receptor.
