Si Yunlong, Yao Yuan, Jaramillo Ayala Gabriela, Li Xumin, Han Qiuyu, Zhang Wenlu, Xu Xuejiao, Tai Guihua, Mayo Kevin H, Zhou Yifa, Su Jiyong
Engineering Research Center of Glycoconjugates Ministry of Education, Jilin Provincial Key Laboratory of Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Northeast Normal University, Changchun 130024, China; Jiangsu Key Laboratory of Brain Disease and Bioinformation, Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, Xuzhou 221004, China.
Media Academy, Jilin Engineering Normal University, Changchun, China.
Biochim Biophys Acta Gen Subj. 2021 Jan;1865(1):129755. doi: 10.1016/j.bbagen.2020.129755. Epub 2020 Oct 2.
The structure of human galectin-16 (Gal-16) has yet to be solved, and its function has remained elusive.
X-ray crystallography was used to determine the atomic structures of Gal-16 and two of its mutants. The Gal-16 oligomer state was investigated by gel filtration, its hemagglutination activity was determined along with its ability to bind lactose using ITC. The cellular distribution of EGFP-tagged Gal-16 in various cell lines was also investigated, and the interaction between Gal-16 and c-Rel was assessed by pull-down studies, microscale thermophoresis and immunofluorescence.
Unlike other galectins, Gal-16 lacks the ability to bind the β-galactoside lactose. Lactose binding could be regained by replacing an arginine (Arg55) with asparagine, as shown in the crystal structures of two lactose-loaded Gal-16 mutants (R55N and R55N/H57R). Gal-16 was also shown to be monomeric by gel filtration, as well as in crystal structures. Thus, this galectin could not induce erythrocyte agglutination. EGFP-tagged Gal-16 was found to be localized mostly in the nucleus of various cell types, and can interact with c-Rel, a member of NF-κB family.
Gal-16 exists as a monomer and its ligand binding is significantly different from that of other prototype galectins, suggesting that it has a novel function(s). The interaction between Gal-16 and c-Rel indicates that Gal-16 may regulate signal transduction pathways via the c-Rel hub in B or T cells at the maternal-fetal interface.
The present study lays the foundation for further studies into the cellular and physiological functions of Gal-16.
人半乳糖凝集素-16（Gal-16）的结构尚未解析，其功能也仍不清楚。
采用X射线晶体学确定Gal-16及其两个突变体的原子结构。通过凝胶过滤研究Gal-16的寡聚状态，利用等温滴定量热法（ITC）测定其血凝活性及其结合乳糖的能力。还研究了绿色荧光蛋白（EGFP）标记的Gal-16在各种细胞系中的细胞分布，并通过下拉实验、微量热泳动和免疫荧光评估Gal-16与c-Rel之间的相互作用。
与其他半乳糖凝集素不同，Gal-16缺乏结合β-半乳糖苷乳糖的能力。如两个负载乳糖的Gal-16突变体（R55N和R55N/H57R）的晶体结构所示，用天冬酰胺取代精氨酸（Arg55）可恢复乳糖结合能力。凝胶过滤以及晶体结构均显示Gal-16为单体。因此，这种半乳糖凝集素不能诱导红细胞凝集。发现EGFP标记的Gal-16主要定位于各种细胞类型的细胞核中，并且可以与NF-κB家族成员c-Rel相互作用。
Gal-16以单体形式存在，其配体结合与其他原型半乳糖凝集素显著不同，表明它具有新功能。Gal-16与c-Rel之间的相互作用表明，Gal-16可能在母胎界面通过B或T细胞中的c-Rel枢纽调节信号转导途径。
本研究为进一步研究Gal-16的细胞和生理功能奠定了基础。
