CK8寡糖链结构及翻译水平改变与人肝癌细胞转移相关性研究

Alteration of CK8 Both in Its Expression Level and Its Glycan Parts Related to HCC Metastatic Ability

糖组学方法筛查人肝癌细胞转移过程中发挥重要作用的核心岩藻糖基化蛋白质分子,解析比较筛出的差异蛋白——细胞角蛋白8(CK8)翻译及糖基化修饰改变与人肝癌细胞转移潜能的关系.应用双向电泳(2-DE)、凝集素亲和印迹、凝集素亲和沉淀联合质谱分析技术,筛查并验证与肝癌转移相关的核心岩藻糖基化蛋白;应用细胞免疫荧光和蛋白质免疫印迹检测CK8的蛋白质表达情况;应用免疫沉淀结合多种凝集素亲和印迹,推测其与肝癌转移相关的寡糖链结构改变.研究发现,3种不同转移潜能人肝癌细胞Hep3B、MHCC97-L和MHCC97-H的扁豆凝集素(LCA)亲和印迹表达谱中,分子质量55～60ku、等电点4～6区域处有核心岩藻糖基化蛋白呈差异表达,质谱鉴定为CK8.LCA亲和沉淀及蛋白质印迹进一步验证CK8异常核心岩藻糖基化与肝癌转移相关;研究发现,CK8分布于细胞浆内,在MHCC97-L和MHCC97-H细胞中蛋白质表达水平较Hep3B高,在MHCC97-H中与LCA和蓖麻凝集素(RCA-1)的亲和力较Hep3B强.以上结果提示,2-DE和凝集素印迹技术联合MALDI-TOF-MS/MS分析可用于筛查疾病过程相关的异常糖基化蛋白质分子,CK8蛋白水平、核心岩藻糖基化及β-1,4末端半乳糖基化的增加均与肝癌细胞转移潜能相关.

A glycomic method was used to screen the aberrantly α1-6 fucosylated glycoproteins related to HCC metastasis and analyze the alteration of CK8 both in its expression level and its glycan parts associated with metastatic ability. Based on the approach, 2-DE coupled with lectin affinity blot, lectin affinity precipitation followed by MALDI-TOF-MS/MS, the lens culinaris agglutinin （LCA） affinity glycoprotein profiles from MHCC97-L and MHCC97-H cells, two higher metastatic HCC cell lines, were obtained, in which a differentially displayed protein spot was indicated when compared with Hep3B, in the region within 55-60 ku in molecular mass and 4 -6 in isoelectric point. The identification result was CK8 by MALDI-TOF-MS/MS. To confirm the relation between increased core-fucosylation of CK8 and HCC metastasis, LCA affinity precipitation was used to extract the α1-6 fucosylated glycoproteins, followed by Western blot. And it was found that CK8 was highly fucosylated in both MHCC97-L and MHCC97-H cells compared to Hep3B. Immunofluorescence analysis and Western blot were used to detect its intracellular localization and its protein expression levels, indicating that CK8 distributed in cytoplasm and increased protein expressions in MHCC97-L and MHCC97-H cell lines. And further lectin binding studies found that CK8 has a high affinity for Con A in both MHCC97-H and Hep3B cells, indicating that CK8 was a glycoprotein with high-mannose type N-glycans. But the amount of the lectin RCA-1 binding to CK8 was greater in MHCC97-H than Hep3B, suggesting that CK8 contained the increased terminal galactose residues β-1, 4-1inked to GlcNAc in MHCC97-H. All the results suggested that the increase of CK8 in its protein expression level, core-fucosylation and terminal gal 131,4 GlcNAc disaccharides might be related to HCC metastatic ability.