Liu B, Offner G D, Nunes D P, Oppenheim F G, Troxler R F
Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, 02118, USA.
Biochem Biophys Res Commun. 1998 Sep 29;250(3):757-61. doi: 10.1006/bbrc.1998.9390.
High molecular weight salivary mucin (MG1) is an important component of saliva, contributing to the lubricative and tissue-protective functions of this biological fluid. We have shown previously that the human mucin gene MUC5B is expressed at high levels in sublingual gland and is a significant constituent of MG1. Since many epithelia express multiple mucin genes, it seemed likely that MG1 in salivary secretions is also a heterogeneous mixture of mucin gene products. The aim of this study was to determine whether MUC4, a mucin shown in Northern blotting experiments to be expressed in salivary glands, was a significant protein component of MG1 in salivary secretions. Two cDNA clones containing MUC4 tandem repeats were isolated from a human submandibular gland cDNA library. In addition, recombinant MUC4 produced in a bacterial expression system cross-reacted with an antibody directed against deglycosylated MG1. This shows conclusively that human salivary mucin MG1 contains both MUC5B and MUC4 gene products suggesting that each mucin may perform distinct functions in the oral cavity.
高分子量唾液粘蛋白（MG1）是唾液的重要组成部分，有助于这种生物流体的润滑和组织保护功能。我们之前已经表明，人类粘蛋白基因MUC5B在舌下腺中高水平表达，并且是MG1的重要组成部分。由于许多上皮细胞表达多种粘蛋白基因，唾液分泌物中的MG1似乎也可能是粘蛋白基因产物的异质混合物。本研究的目的是确定在Northern印迹实验中显示在唾液腺中表达的粘蛋白MUC4是否是唾液分泌物中MG1的重要蛋白质成分。从人下颌下腺cDNA文库中分离出两个含有MUC4串联重复序列的cDNA克隆。此外，在细菌表达系统中产生的重组MUC4与针对去糖基化MG1的抗体发生交叉反应。这确凿地表明，人类唾液粘蛋白MG1包含MUC5B和MUC4基因产物，表明每种粘蛋白可能在口腔中发挥不同的功能。
