Lectins (hemagglutinins) are a type of proteins that could recognize different sugar structures and specifically initiate reversible binding with them. Though they have been universally found in a variety of organisms, they are exceptionally abundant in legumes. From the initial finding of agglutinating red blood cells to the discovery of recognizing carbohydrates on cell membranes, multiple functions of lectins have been gradually unveiled by numerous researchers across a century. Based on its carbohydrate-binding property, lectins have found great value in the study of glycomics. Many lectin-based biological tools, like lectin affinity chromatography, lectin blotting, lectin histochemistry, lectin microarray and lectin-based biosensor have been developed and applied to the study of glycoproteins. Besides, lectins are also reported to be potential agents for anti-insect, anti-fungi, anti-HIV, anti-bacterial and anti-tumor applications. / The present study focuses on the isolation of a new hemagglutinin from an edible legume, exploration of its anti-colorectal cancer effect and mechanisms, its cytokine inducing function and anti-HIV activities. The protein was purified by liquid chromatography techniques which entailed affinity chromatography on Affi-Gel Blue Gel, ion exchange chromatography on Mono Q and gel filtration on Superdex 75 with an FPLC system. The hemagglutinating activity of this hemagglutinin was demonstrated to be ion-dependent and stable over a wide range of temperatures (20-60℃) and pH (2-11) values. Like most of the lectins or hemagglutinins, this novel hemagglutinin could also attenuate the activity of HIV-1 reverse transcriptase. / This hemagglutinin could potently suppress the proliferation of colorectal carcinoma HCT116 cells and colorectal adenocarcinoma HT29 cells. It induced cell cycle arrest in G0/G1 phase, downregulated the expression of Cyclin D1 and upregulated P21expression. The protein initially bound on the cell membranes most probably through glycoproteins and subsequently entered the cytoplasm, which was achieved as early as 3h post treatment. The hemagglutinin was found to be preferentially localized in Golgi apparatus and initiated aggregation of the Golgi apparatus, which may possibly attenuate its protein processing capacity by reducing total superficial area or even partially blocking the transportation of proteins from the endoplasmic reticulum (ER). The impaired protein reception ability of Golgi apparatus may lead to the protein accumulation in the ER and induce cell apoptosis. Accordingly, two ER stress sensors (IRE1α and ATF6) and one late product of ER stress (CHOP) were found to up-regulated. Apoptosis-inducing effect of this hemagglutinin on HT29 and HCT116 cells were further confirmed using methods based on different principles. Cells treated with the hemagglutinin were observed to undergo obvious chromatin condensation, mitochondrial membrane depolarization and phosphatidylserine exposure. An apoptosis initiator (Apaf-1) and one important indicator (cleaved PARP) of cell apoptosis were accordingly detected. Besides, intraperitoneal administration of this hemagglutinin to colorectal tumor bearing nude mice could slow down the growth of tumors. / At last, this hemagglutinin exerted an immunomodulatory function on splenocytes by stimulating the mRNA expression level of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), interferon- gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α). Secretion of IL-1β and IL-2 from splenocytes also increased with the concentration of this hemagglutinin. / In a short conclusion, we have isolated a new hemagglutinin with anti-HIV RT, anti-colorectal cancer and immunomodulatory activities. / 凝集素（血凝素）是一类能够识别不同糖结构并能和它们发生可逆性结合的蛋白。虽然他们在许多生物体内均有发现，但这类蛋白在豆科植物中的含量尤其丰富。经过一个多世纪来众多研究者的努力，从最初认识到其具有红血细胞凝集功能到糖类识别作用，凝集素的诸多功能已被逐步挖掘。基于其独特的糖结构识别特性，凝集素在糖组学的研究中具有重大意义。许多基于凝集素的生物方法，如凝集素亲和层析法，凝集素印迹法，凝集素组织化学，凝集素生物芯片以及基于凝集素的生物传感器已被研究出来, 并用于研究糖蛋白。除此之外，研究表明，凝集素还具有抗虫，抗真菌，抗HIV，抗细菌和抗癌等活性。 / 该凝集素可以极大抑制结肠直肠癌HCT116细胞和结直肠腺癌HT29细胞增殖，引发细胞周期停滞，分别下调和上调Cyclin D1和P21的表达。该蛋白极有可能首先通过和细胞表面的糖蛋白结合而附在细胞膜上，然后进入细胞内。该过程可在往细胞培养液内加入该蛋白后的3小时内完成。该凝集素优先与细胞内的高尔基体结合，随后引发高尔基体聚集。该聚集作用可能会通过减少高尔基体总表面积甚至阻塞内质网和高尔基体间的蛋白运输，进而减弱高尔基体处理蛋白质的能力。当高尔基体接受蛋白的能力降低时，蛋白可能会堆积在内质网上并进一步引发细胞程序性死亡。相应地，两个内质网应激感受蛋白IRE1α和 ATF6以及内质网应激后期产物CHOP均被发现上调。该凝集素对HT29细胞和HCT116细胞的凋亡诱导作用采用不同的方法进行了进一步的确认，这些方法都是基于不同检测原理进行的。结果表明，该凝集素可导致细胞产生明显的染色质凝缩，线粒体膜电位去极化和磷脂酰丝氨酸外翻。与此相应地，凋亡启动蛋白Apaf-1和凋亡后期蛋白(被剪切的PARP)可在处理后的细胞中检测到。通过腹腔注射的方法给接种大肠癌细胞的裸鼠给药可降低肿瘤的生长速度。 / 本研究的工作包括：从一种可食用豆类中提取一种新的凝集素；检测其抗大肠癌的作用和机制；研究其细胞素诱导作用以及抗HIV活性。该蛋白采用液相色谱法分离提纯，其中包括亲和层析柱Affi-Gel Blue Gel, 离子交换层析柱Mono Q 和凝胶层析柱Superdex 75，后两种层析法在FPLC系统上操作。该蛋白的红血细胞凝集作用具有金属阳离子依赖性，并在20-60℃和pH2-11范围内保持活性稳定。像许多其它的凝集素一样，该蛋白也可以削弱HIV逆转录酶活性。 / 最后，该蛋白还具有免疫调节作用，它可促进白细胞介素-2，白细胞介素-6，白细胞介素-1β，干扰素-γ和肿瘤坏死因数-α在mRNA水平上的表达并刺激白细胞介素-2和细胞介素-1β的分泌。 / 综上所诉，本研究分离提纯了一种新凝集素，它具有抗HIV，抗大肠癌和免疫调节作用。 / Dan, Xiuli. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 153-170). / Abstracts also in Chinese. / Title from PDF title page (viewed on 05, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_1291464 |
| Date | January 2015 |
| Contributors | Dan, Xiuli (author.), Ng, Tzi Bun (thesis advisor.), Chinese University of Hong Kong Graduate School. Division of Biomedical Sciences. (degree granting institution.) |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography, text |
| Format | electronic resource, electronic resource, remote, 1 online resource (xx, 170 leaves) : illustrations (some color), computer, online resource |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons "Attribution-NonCommercial-NoDerivatives 4.0 International" License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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