唾液酸化與岩藻醣化對肺癌細胞中上皮生長激素受器的聚合作用及活性調控之探討

蛋白質醣化是一項重要的轉譯後修飾，可調節蛋白質的摺疊與功能表現。過去研究顯示，癌細胞中異常的醣化作用可能影響癌症的發生與惡化。在目前的研究中，我們試著藉由炔化類醣(alkynyl sugars)比較兩株源自同細胞但具有不同侵襲力的肺癌細胞株CL1-0與CL1-5之中受唾液酸化與岩藻醣化的蛋白質。最初的結果發現，在較具侵襲力的CL1-5細胞中可觀察到比起CL1-0更高量之唾液酸化與岩藻醣化蛋白質的表現。接下來，我們定出CL1-5中受高量唾液酸化的蛋白質，並從中選定上皮細胞生長激素受器(EGFR)更深入探討唾液酸化對其功能之影響。我們定出EGFR在兩種細胞株中醣鍊的序列結構，並且確認了EGFR的確在CL1-5中較CL1-0受到更高程度的唾液酸化。有趣的是，我們也從醣鍊定序的結果中觀察到CL1-5中的EGFR有較CL1-0高量的岩藻醣化現象，與先前利用炔化類岩藻醣比較兩細胞中蛋白質醣化的結果相符合。進一步的實驗中，我們發現表現高量唾液酸轉移酶的CL1-5以及過量表現岩藻醣轉移酶4/6的A549細胞，其EGFR在受質EGF處理下，發生聚合、磷酸化，以及下游訊息活化的程度都會受到抑制。然而，若在CL1-5中抑制岩藻醣轉移酶8的表現，則減弱了EGFR的聚合與磷酸化，顯示核心岩藻醣化(core-fucosylation)具有強化EGFR活性的效果。此影響聚合與醣化的關聯已經由唾液酸水解酶與岩藻醣水解酶的處理而得到證實，並且發現唾液酸化與岩藻醣化程度的高低的確會影響肺癌細胞受EGF刺激所引發的侵襲現象。本研究成果提供了一個新的觀點，唾液酸化與岩藻醣化程度的上升，特別是在某些EGFR過量表現的癌細胞中，可能具有拮抗癌細胞發育的作用。

關鍵字

唾液酸；岩藻醣；上皮細胞生長激素受器；醣蛋白質體學；醣定序

並列摘要

Glycosylation is an important post-translational modification, which regulates proteins folding and functional expression. Previous studies have shown that, abnormal glycosylation in tumor cells can participate in cancer progression and malignancy. In the current study, we compared the sialylated and fucosylated proteins with alkynyl sugars in different lung cancer cell lines, CL1-0 and CL1-5, two subpopulations derived from the same parental cell line but with distinct invasiveness. Our initial experiments demonstrated that CL1-5, the highly aggressive cells, expressed more sialylated and fucosylated proteins than CL1-0. At next step, we identified the unique sialylated proteins in CL1-5. Among them, we chose epidermal growth factor receptor (EGFR) to further study the role of sialylation on its function. Based on glycan analysis, we validated the distinct sialylation level of EGFR in both cells. Interestingly, we also observed higher fucosylation of EGFR in CL1-5 than in CL1-0, corresponding to the comparison of whole proteins glycosylation in both cells using alkynyl fucose. Further study suggested that overexpression of sialyltranssferases in CL1-5 and

並列關鍵字

Sialic acid ； Fucose ； EGFR ； Glycoproteomics ； glycan sequencing

參考文獻

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唾液酸化與岩藻醣化對肺癌細胞中上皮生長激素受器的聚合作用及活性調控之探討

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