From the Departments of Pediatrics,
From the Departments of Pediatrics.
J Biol Chem. 2019 Jan 11;294(2):662-678. doi: 10.1074/jbc.RA118.006022. Epub 2018 Nov 14.
(Pa) expresses an adhesin, flagellin, that engages the mucin 1 (MUC1) ectodomain (ED) expressed on airway epithelia, increasing association of MUC1-ED with neuraminidase 1 (NEU1) and MUC1-ED desialylation. The MUC1-ED desialylation unmasks both cryptic binding sites for Pa and a protease recognition site, permitting its proteolytic release as a hyperadhesive decoy receptor for Pa. We found here that intranasal administration of Pa strain K (PAK) to BALB/c mice increases MUC1-ED shedding into the bronchoalveolar compartment. MUC1-ED levels increased as early as 12 h, peaked at 24-48 h with a 7.8-fold increase, and decreased by 72 h. The a-type flagellin-expressing PAK strain and the b-type flagellin-expressing PAO1 strain stimulated comparable levels of MUC1-ED shedding. A flagellin-deficient PAK mutant provoked dramatically reduced MUC1-ED shedding compared with the WT strain, and purified flagellin recapitulated the WT effect. In lung tissues, Pa increased association of NEU1 and protective protein/cathepsin A with MUC1-ED in reciprocal co-immunoprecipitation assays and stimulated MUC1-ED desialylation. NEU1-selective sialidase inhibition protected against Pa-induced MUC1-ED desialylation and shedding. In Pa-challenged mice, MUC1-ED-enriched bronchoalveolar lavage fluid (BALF) inhibited flagellin binding and Pa adhesion to human airway epithelia by up to 44% and flagellin-driven motility by >30%. Finally, Pa co-administration with recombinant human MUC1-ED dramatically diminished lung and BALF bacterial burden, proinflammatory cytokine levels, and pulmonary leukostasis and increased 5-day survival from 0% to 75%. We conclude that Pa flagellin provokes NEU1-mediated airway shedding of MUC1-ED, which functions as a decoy receptor protecting against lethal Pa lung infection.
(Pa) 表达一种黏附素，鞭毛蛋白，与气道上皮细胞表达的粘蛋白 1 (MUC1) 外显子 (ED) 结合，增加 MUC1-ED 与神经氨酸酶 1 (NEU1) 的结合，并使 MUC1-ED 去唾液酸化。MUC1-ED 的去唾液酸化使 Pa 的两个隐蔽结合位点和一个蛋白酶识别位点暴露，从而将其作为 Pa 的超黏附诱饵受体进行蛋白水解释放。我们在这里发现，鼻内给予 Pa 株 K (PAK) 可增加 BALB/c 小鼠的 MUC1-ED 脱落至支气管肺泡腔。MUC1-ED 水平早在 12 小时就开始增加，在 24-48 小时达到高峰，增加了 7.8 倍，并在 72 小时下降。表达 a 型鞭毛蛋白的 PAK 株和表达 b 型鞭毛蛋白的 PAO1 株刺激了相当水平的 MUC1-ED 脱落。与野生型菌株相比，缺乏 flagellin 的 PAK 突变体引起的 MUC1-ED 脱落明显减少，而纯化的 flagellin 则再现了野生型菌株的效应。在肺组织中，Pa 增加了 NEU1 和保护性蛋白/组织蛋白酶 A 与 MUC1-ED 的结合，在相互免疫沉淀测定中，并刺激 MUC1-ED 的去唾液酸化。NEU1 选择性唾液酸酶抑制可防止 Pa 诱导的 MUC1-ED 去唾液酸化和脱落。在 Pa 攻击的小鼠中，MUC1-ED 富集的支气管肺泡灌洗液 (BALF) 通过 44% 抑制了鞭毛蛋白结合和 Pa 对人气道上皮的粘附，通过 >30% 抑制了鞭毛蛋白驱动的运动。最后，Pa 与重组人 MUC1-ED 共同给药大大降低了肺部和 BALF 中的细菌负荷、促炎细胞因子水平以及肺部白细胞淤滞，并将 5 天的存活率从 0%提高到 75%。我们得出结论，Pa 鞭毛蛋白引发了 NEU1 介导的气道 MUC1-ED 脱落，该脱落作为一种诱饵受体，可防止致命的 Pa 肺部感染。
