Jumblatt Marcia M, Imbert Yoannis, Young William W, Foulks Gary N, Steele Pamela S, Demuth Donald R
Department of Ophthalmology and Visual Science, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Infect Immun. 2006 Jul;74(7):4058-63. doi: 10.1128/IAI.01951-05.
The tear film is a complex mixture of secreted fluid, ions, proteins, glycoproteins, and lipids that lubricates and protects the ocular surface. Recently, several antimicrobial peptides have been described in the tear fluid. In this study, we describe the presence of the large secreted glycoprotein gp340 in the tear film. Western blot analysis showed that gp340 is abundant in secreted tears and in the lacrimal glands. Lesser amounts of gp340 were detected in the cornea and conjunctiva. Consistent with Western blot data, reverse transcription-PCR and real-time quantitative PCR showed that gp340 transcripts were abundant in lacrimal gland tissue and were also present in the cornea and conjunctiva. Immunohistochemistry localized gp340 to the acinar cells of the lacrimal gland and the deeper layers of the conjunctival epithelium. gp340 was not detected in conjunctival goblet cells. In the cornea, gp340 was present only in a peripheral band of basal epithelial cells, suggesting that gp340 may play a role in the cycle of corneal epithelial renewal. To determine if tear film gp340 may function as a bacterial agglutinin as it does in saliva, tears were incubated with streptococcal cells and the formation of bacterial aggregates was monitored. Addition of tears to late-exponential-phase Streptococcus mutans cells resulted in time- and dose-dependent aggregation of the bacteria. Furthermore, Western blot analysis confirmed the presence of cell-associated gp340 in isolated bacterial aggregates. The ocular pathogen Staphylococcus aureus, but not Pseudomonas aeruginosa, also aggregated when incubated with tears. These results suggest that gp340 is a normal component of the tear film and that the glycoprotein may function as a bacterial agglutinin.
泪膜是由分泌液、离子、蛋白质、糖蛋白和脂质组成的复杂混合物，可润滑和保护眼表。最近，在泪液中发现了几种抗菌肽。在本研究中，我们描述了泪膜中存在大量分泌型糖蛋白gp340。蛋白质印迹分析表明，gp340在分泌的泪液和泪腺中含量丰富。在角膜和结膜中检测到的gp340量较少。与蛋白质印迹数据一致，逆转录PCR和实时定量PCR显示，gp340转录本在泪腺组织中丰富，在角膜和结膜中也存在。免疫组织化学将gp340定位到泪腺的腺泡细胞和结膜上皮的深层。在结膜杯状细胞中未检测到gp340。在角膜中，gp340仅存在于基底上皮细胞的外周带，这表明gp340可能在角膜上皮更新周期中起作用。为了确定泪膜gp340是否像在唾液中那样发挥细菌凝集素的作用，将眼泪与链球菌细胞一起孵育，并监测细菌聚集体的形成。将眼泪添加到对数后期的变形链球菌细胞中会导致细菌出现时间和剂量依赖性聚集。此外，蛋白质印迹分析证实分离的细菌聚集体中存在与细胞相关的gp340。眼部病原体金黄色葡萄球菌与眼泪孵育时也会聚集，但铜绿假单胞菌不会。这些结果表明，gp340是泪膜的正常成分，并且该糖蛋白可能发挥细菌凝集素的作用。
