Lips K S, Kaltner H, Reuter G, Stierstorfer B, Sinowatz F, Gabius H J
Institut für Physiologische Chemie, Tierärztliche Fakultät, Ludwig-Maximilians-Universität, München, Germany.
Histol Histopathol. 1999 Jul;14(3):743-60. doi: 10.14670/HH-14.743.
The duplication of genes for recognition molecules and the ensuing diversification of the members of such families generate complex groups of homologous proteins. One example are galactoside-specific lectins whose sequences display constant features related to sugar binding, the galectins. Based on the inverse abundance of the chicken galectins CG-14 and CG-16 in adult intestine and liver, these two lectins represent a model to comparatively study expression of the related proteins and the galectin-reactive sites (glycoproteins and glycolipids) biochemically and histochemically. Functional overlap and/or acquisition of distinct functions would be reflected in qualitative and/or quantitative aspects of ligand display. Using five different stages of embryogenesis, differential regulation of the two galectins was detected in liver and intestine. The clear preference for one galectin (CG-14) was observed in intestine already at rather early stages, whereas equivalence for both proteins was noted in liver from day 12 to day 18 prior to hatching, as seen by ELISA assays and Western blot analysis. Presentation of galectin-reactive glycoproteins showed a tendency for gradual increase in both organs. Galectin-blotting analysis revealed primarily very similar patterns of positive bands at the different stages of development and only few quantitative and qualitative changes. The reactivity of glycolipids in a solid-phase assay was more variable, even surpassing the response of extracts of the adult organ at several embryonic stages. While the localization patterns of the galectins and galectin-reactive sites were nearly indistinguishable in the liver, intestinal tissue differed with respect to the placement and accessibility of binding sites. Thus, the results suggest a differential regulation of galectin activities in the two organs. As a sum they resemble the course of development of availability of glycoprotein ligands in vitro. These findings support the notion for a partial functional redundancy in this family. The described approach to employ galectin-specific antibodies and the labeled galectins as tools to assess presentation of ligands is suggested to be of general relevance to address the question of distinct vs. overlapping functions of related recognition molecules.
识别分子基因的复制以及此类家族成员随后的多样化产生了复杂的同源蛋白群体。一个例子是半乳糖苷特异性凝集素，其序列显示出与糖结合相关的恒定特征，即半乳糖凝集素。基于成年鸡肠道和肝脏中鸡半乳糖凝集素CG - 14和CG - 16的反向丰度，这两种凝集素代表了一个模型，可用于从生化和组织化学角度比较研究相关蛋白及半乳糖凝集素反应位点（糖蛋白和糖脂）的表达。功能重叠和/或获得不同功能将反映在配体展示的定性和/或定量方面。利用胚胎发育的五个不同阶段，在肝脏和肠道中检测到了这两种半乳糖凝集素的差异调节。通过ELISA分析和蛋白质印迹分析发现，在相当早期阶段，肠道中就已明显偏好一种半乳糖凝集素（CG - 14），而在孵化前第12天到第18天的肝脏中，两种蛋白表现相当。半乳糖凝集素反应性糖蛋白的呈现显示出在两个器官中都有逐渐增加的趋势。半乳糖凝集素印迹分析显示，在发育的不同阶段，阳性条带的模式基本非常相似，只有很少的定量和定性变化。在固相分析中，糖脂的反应性变化更大，甚至在几个胚胎阶段超过了成年器官提取物的反应。虽然半乳糖凝集素和半乳糖凝集素反应位点在肝脏中的定位模式几乎无法区分，但肠道组织在结合位点的位置和可及性方面存在差异。因此，结果表明这两种器官中半乳糖凝集素活性存在差异调节。总体而言，它们类似于体外糖蛋白配体可利用性的发育过程。这些发现支持了该家族中存在部分功能冗余的观点。所描述的使用半乳糖凝集素特异性抗体和标记的半乳糖凝集素作为工具来评估配体呈现的方法，被认为对于解决相关识别分子的不同功能与重叠功能问题具有普遍相关性。
