Lohr M, Lensch M, André S, Kaltner H, Siebert H-C, Smetana K, Sinowatz F, Gabius H-J
Institute of Physiological Chemistry, Ludwig-Maximilians-University, Munich, Germany.
Folia Biol (Praha). 2007;53(4):109-28.
Following the detection of individual members of the family of galectins it is an obvious challenge to define the extent of functional overlap/divergence among these proteins. As a step to address this issue a comparative profiling has been started in the mouse as a model organism, combining sequence analysis, expression patterns and structural features in the cases of the homodimeric galectins-1, -2 and -7. Close relationship was apparent at the level of global gene organization. Scrutiny of the proximal promoter regions for putative transcription-factor-binding sites by two search algorithms uncovered qualitative and quantitative differences with potential to influence the combinatorial functionality of regulatory sequences. RT-PCR mapping with samples from an array of 17 organs revealed significant differences, separating rather ubiquitous gene expression of galectin-1 from the more restricted individual patterns of galectins-2 and -7. Using specific antisera obtained by affinity depletion including stringent controls to ascertain lack of cross-reactivity these results were corroborated at the level of galectin localization in fixed tissue sections. Nuclear presence was seen in the case of galectin-1. In addition to nonidentical expression profiles the mapping of the carbohydrate recognition domains of galectins-1 and -7 by homology modelling and docking of naturally occurring complex tetra- and pentasaccharides disclosed a series of sequence deviations which may underlie disparate affinities for cell surface glycans/glycomimetic peptides. In view of applicability the presented data can serve as useful reference to delineate changes with respect to disease and in genetically engineered models. To enable more general conclusions on the galectin network it is warranted to further pursue this combined approach within this lectin family.
在检测到半乳糖凝集素家族的各个成员之后，定义这些蛋白质之间功能重叠/差异的程度显然是一项挑战。作为解决这一问题的一个步骤，已经开始在小鼠这一模式生物中进行比较分析，结合了同源二聚体半乳糖凝集素-1、-2和-7的序列分析、表达模式和结构特征。在整体基因组织水平上，明显存在密切关系。通过两种搜索算法仔细研究近端启动子区域中假定的转录因子结合位点，发现了定性和定量差异，这些差异有可能影响调控序列的组合功能。用来自17个器官阵列的样本进行RT-PCR定位，发现了显著差异，将半乳糖凝集素-1相当普遍的基因表达与半乳糖凝集素-2和-7更具限制性的个体模式区分开来。使用通过亲和去除获得的特异性抗血清，包括严格的对照以确定无交叉反应性，这些结果在固定组织切片中的半乳糖凝集素定位水平上得到了证实。在半乳糖凝集素-1的情况下观察到细胞核内存在。除了不同的表达谱之外，通过同源建模以及天然存在的复合四糖和五糖的对接对半乳糖凝集素-1和-7的碳水化合物识别结构域进行定位，揭示了一系列序列偏差，这些偏差可能是对细胞表面聚糖/糖模拟肽具有不同亲和力的基础。鉴于适用性，所呈现的数据可作为有用的参考，以描绘疾病和基因工程模型方面的变化。为了对半乳糖凝集素网络得出更普遍的结论，有必要在这个凝集素家族中进一步采用这种综合方法。
