Cederfur Cecilia, Malmström Johan, Nihlberg Kristian, Block Mattias, Breimer Michael E, Bjermer Leif, Westergren-Thorsson Gunilla, Leffler Hakon
MIG (Microbiology, Immunology, Glycobiology), Dept. of Laboratory Medicine Lund, Sweden.
Biochim Biophys Acta. 2012 Sep;1820(9):1429-36. doi: 10.1016/j.bbagen.2011.12.016. Epub 2012 Jan 4.
Galectins, a family of small carbohydrate binding proteins, have been implicated in regulation of inflammatory reactions, including asthma and fibrosis in the lungs. Galectins are found in cells of the airways and in airway secretions, but their glycoprotein ligands there have only been studied to a very limited extent.
Bronchoalveolar lavage (BAL) fluid from mild asthmatics and healthy volunteers were fractionated by affinity chromatography on the immobilized galectins. Total (10-30 μg) and galectin bound (~1-10 μg) protein fractions were identified, quantified and compared using shot-gun proteomics and spectral counts.
About 175 proteins were identified in unfractionated BAL-fluid, and about 100 bound galectin-3 and 60 bound galectin-8. These included plasma glycoproteins, and typical airway proteins such as SP-A2, PIGR and SP-B. The concentration of galectin-binding proteins was 100-300 times higher than the concentration of galectins in BAL.
The low relative concentration of galectins in BAL makes it likely that functional interactions with glycoproteins occur at sites rich in galectin, such as cells of the airways, rather than the extracellular fluid itself. The profile of galectin bound proteins differed between samples from asthma patients and healthy subjects and correlated with the presence of fibroblasts or eosinophils. This included appearance of a specific galectin-8-binding glycoform of haptoglobin, previously shown to be increased in serum in other inflammatory conditions.
It is technically feasible to identify galectin-binding glycoproteins in low concentration patient samples such as BAL-fluid, to generate biomedically interesting results. This article is part of a Special Issue entitled Glycoproteomics.
半乳糖凝集素是一类小型碳水化合物结合蛋白家族，与包括哮喘和肺纤维化在内的炎症反应调节有关。半乳糖凝集素存在于气道细胞和气道分泌物中，但对其在那里的糖蛋白配体的研究非常有限。
通过固定化半乳糖凝集素的亲和色谱法对轻度哮喘患者和健康志愿者的支气管肺泡灌洗（BAL）液进行分级分离。使用鸟枪法蛋白质组学和光谱计数法对总蛋白组分（10 - 30μg）和与半乳糖凝集素结合的蛋白组分（约1 - 10μg）进行鉴定、定量和比较。
在未分级的BAL液中鉴定出约175种蛋白质，约100种与半乳糖凝集素-3结合，60种与半乳糖凝集素-8结合。这些包括血浆糖蛋白以及典型的气道蛋白，如SP-A2、PIGR和SP-B。BAL中半乳糖凝集素结合蛋白的浓度比半乳糖凝集素的浓度高100 - 300倍。
BAL中半乳糖凝集素的相对浓度较低，这使得其与糖蛋白的功能相互作用可能发生在富含半乳糖凝集素的部位，如气道细胞，而不是细胞外液本身。哮喘患者和健康受试者样本中与半乳糖凝集素结合的蛋白质谱不同，且与成纤维细胞或嗜酸性粒细胞的存在相关。这包括出现一种特定的与半乳糖凝集素-8结合的触珠蛋白糖型，此前已证明在其他炎症条件下血清中该糖型会增加。
在低浓度患者样本如BAL液中鉴定半乳糖凝集素结合糖蛋白在技术上是可行的，并能产生具有生物医学意义的结果。本文是名为“糖蛋白质组学”的特刊的一部分。
