Department of Microbiology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.
Department of Immunology and Infectious Diseases, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.
Front Immunol. 2023 Jun 8;14:1211336. doi: 10.3389/fimmu.2023.1211336. eCollection 2023.
The colonic mucus bilayer is the first line of innate host defense that at the same time houses and nourishes the commensal microbiota. The major components of mucus secreted by goblet cells are MUC2 mucin and the mucus-associated protein, FCGBP (IgGFc-binding protein). In this study, we determine if FCGBP and MUC2 mucin were biosynthesized and interacted together to spatially enhance the structural integrity of secreted mucus and its role in epithelial barrier function. MUC2 and FCGBP were coordinately regulated temporally in goblet-like cells and in response to a mucus secretagogue but not in CRISPR-Cas9 gene-edited cells. Whereas ~85% of MUC2 was colocalized with FCGBP in mucin granules, ~50% of FCGBP was diffusely distributed in the cytoplasm of goblet-like cells. STRING-db v11 analysis of the mucin granule proteome revealed no protein-protein interaction between MUC2 and FCGBP. However, FCGBP interacted with other mucus-associated proteins. FCGBP and MUC2 interacted via N-linked glycans and were non-covalently bound in secreted mucus with cleaved low molecular weight FCGBP fragments. In , cytoplasmic FCGBP was significantly increased and diffusely distributed in wounded cells that healed by enhanced proliferation and migration within 2 days, whereas, in WT cells, MUC2 and FCGBP were highly polarized at the wound margin which impeded wound closure by 6 days. In DSS colitis, restitution and healed lesions in but not littermates, were accompanied by a rapid increase in mRNA and delayed protein expression at 12- and 15-days post DSS, implicating a potential novel endogenous protective role for FCGBP in wound healing to maintain epithelial barrier function.
结肠黏液双层是先天宿主防御的第一道防线，同时容纳和滋养共生微生物群。由杯状细胞分泌的黏液的主要成分是 MUC2 粘蛋白和与黏液相关的蛋白，FCGBP（IgG Fc 结合蛋白）。在这项研究中，我们确定 FCGBP 和 MUC2 粘蛋白是否被生物合成并相互作用，以空间增强分泌黏液的结构完整性及其在上皮屏障功能中的作用。MUC2 和 FCGBP 在类杯状细胞中时间上协调调节，并对黏液分泌激动剂有反应，但在 CRISPR-Cas9 基因编辑细胞中没有反应。虽然 MUC2 的85%与 FCGBP 在粘蛋白颗粒中共定位，但 FCGBP 的50%在类杯状细胞的细胞质中弥散分布。粘蛋白颗粒蛋白质组的 STRING-db v11 分析显示 MUC2 和 FCGBP 之间没有蛋白-蛋白相互作用。然而，FCGBP 与其他与黏液相关的蛋白相互作用。FCGBP 和 MUC2 通过 N-连接的糖基相互作用，并在分泌的黏液中以非共价键结合，具有切割的低分子量 FCGBP 片段。在 中，细胞质 FCGBP 显著增加，并在 2 天内通过增强增殖和迁移而愈合的伤口细胞中弥散分布，而在 WT 细胞中，MUC2 和 FCGBP 在伤口边缘高度极化，这阻碍了伤口在 6 天内闭合。在 DSS 结肠炎中，快速增加 ，而不是 ，在 12 天和 15 天 DSS 后快速增加 ，提示 FCGBP 在伤口愈合中具有潜在的新型内源性保护作用，以维持上皮屏障功能。
