Assembly and organization of the N-terminal region of mucin MUC5AC: Indications for structural and functional distinction from MUC5B

作者：Jerome Carpenter, Yang Wang, Richa Gupta, Yuanli Li, Prashamsha Haridass, Durai B. Subramani, Boris Reidel, Lisa C. Morton, Caroline Ridley, Wanda K. O’Neal, Marie‐Pierre Buisine, Camille Ehré, David J. Thornton, Mehmet Kesımer · 发表于：Proceedings of the National Academy of Sciences · 年份：2021 · DOI：10.1073/pnas.2104490118 · 被引用次数：90 · 研究领域：Glycosylation and Glycoproteins Research、Carbohydrate Chemistry and Synthesis、Proteoglycans and glycosaminoglycans research

Elevated levels of MUC5AC, one of the major gel-forming mucins in the lungs, are closely associated with chronic obstructive lung diseases such as chronic bronchitis and asthma. It is not known, however, how the structure and/or gel-making properties of MUC5AC contribute to innate lung defense in health and drive the formation of stagnant mucus in disease. To understand this, here we studied the biophysical properties and macromolecular assembly of MUC5AC compared to MUC5B. To study each native mucin, we used Calu3 monomucin cultures that produced MUC5AC or MUC5B. To understand the macromolecular assembly of MUC5AC through N-terminal oligomerization, we expressed a recombinant whole N-terminal domain (5ACNT). Scanning electron microscopy and atomic force microscopy imaging indicated that the two mucins formed distinct networks on epithelial and experimental surfaces; MUC5B formed linear, infrequently branched multimers, whereas MUC5AC formed tightly organized networks with a high degree of branching. Quartz crystal microbalance-dissipation monitoring experiments indicated that MUC5AC bound significantly more to hydrophobic surfaces and was stiffer and more viscoelastic as compared to MUC5B. Light scattering analysis determined that 5ACNT primarily forms disulfide-linked covalent dimers and higher-order oligomers (i.e., trimers and tetramers). Selective proteolytic digestion of the central glycosylated region of the full-length molecule confirmed that MUC5AC forms dimers and h...