Analysis of the role of galectin family and its signaling in the host-response to infection and inflammation.

Galectins是动物凝集素家族的成员，专门识别糖结合物的B-半乳糖苷结构。本研究试图分析Galectins串联重复序列Galectins-8和Galectins-9在免疫细胞中的作用及其信号转导的分子机制。首先，我们研究了Galectin-8对人外周血中性粒细胞活化的影响。结果表明，Galectin-8的糖识别域与基质金属蛋白酶-9(ProMMP9)结合，C端结合整合素αM和ProMMP9。Galectin-8结合可加速中性粒细胞表面原基质金属蛋白酶-9的表达，整合素αM与Galectin-8相互作用可刺激中性粒细胞产生超氧化物。其次，我们比较了Galectins-8和Galectins-9对不同免疫细胞系的细胞凋亡和细胞黏附的影响。Galectin-9可诱导T细胞株Jurkat和Molt-4的凋亡，而Galectin-8则不能。两种Galectins均可介导B细胞系(Namalwa和RPMI-8866)和单核细胞系(THP-1)的细胞与塑料培养板的黏附。在Jurkat细胞中，Galectin-8的一个靶候选被确定为整合素α4，它与细胞黏附有关。第三，利用重组蛋白工程技术，将串联重复型Galectins-8和-9的两个CRD连接的连接多肽区域缺失。连接子缺失的突变体(空Galectins)对蛋白水解酶具有抗药性。半乳糖凝集素在细胞黏附和化学吸引等免疫细胞功能中保持了较高的生物活性。因此，串联重复半乳糖凝集素在天然免疫细胞和细胞系中具有多种作用。他们的主要目标之一可能是整合素。此外，稳定的Galectins将成为Galectin功能分析和免疫疾病药物开发的有用工具。

Galectins are members of an animal lectin family, which specifically recognizes B-galactoside structure of glycoconjugates. In this study, we attempted to analyze the molecular mechanism of the functions and their signaling of tandem repeat galectins, such as galectins-8 and -9 in immune cells. First, we examined the effect of galectin-8 on the activation of human peripheral neutrophils. The results revealed that N-terminal CRD(carbohydrate recognition domain) of galectin-8 bound pormatrix metalloproteinase-9 (proMMP-9) and C-terminal CRD bound integrin αM and proMMP-9. The processing of ProMMP-9 on the surface of neutrophils was accelerated by binding of galectin-8, and the superoxide production in neutrophils was stimulated by the interaction between integrin αM and galectin-8. Second, we compared the effects of galectins-8 and -9 on the apoptosis and cell adhesion in various immune cell lines. Galectin-9 induced apoptosis of T-cell lines (Jurkat and Molt-4), but galectin-8 did not. Both of galectins mediated the cell adhesion to plastic culture plates in B-cell lines(Namalwa, and RPMI-8866) and a monocytic cell (THP-1) in addition of T-cell lines. A target candidate for galectin-8 in Jurkat cells was identified to be integrin α4, which associates with cell adhesion. Third, linker peptide regions joining of the two CRDs of tandem repeat type galectins-8 and -9, were deleted by recombinant protein engineering. The linker-deleted mutants (null galectins) are resistant to proteases. The satble null galectins maintained high biological activities in immune cell functions such as cell adhesion and chemoattraction. Thus, tandem repeat galectins have multile roles in natural immunocytes and cell lines. And one of their main targets may be integrin faimily. Furthermore, the stable galectins must be useful tools for analysis of galectin functions and the development of medicine for immune diseases.