雙特異性去磷酸酶(DUSPs)能將同一個蛋白質上的phosphotyrosine、phosphoserine /threonine去磷酸化。目前已知有部分的DUSPs會參與MAPKs (mitogen-activated protein kinases)負回饋調控及影響細胞週期，但尚有部份小分子量的DUSPs其功能仍未知。DUSPs家族裡某些成員又稱為非典型DUSPs (atypical DUSPs)，因其僅含有catalytic domain。DUPS23是目前已知最小分子量的非典型DUSP，由151個胺基酸組成，分子量約16kDa，功能未知。根據文獻，DUSP23在人類胎兒的各種組織中均有表現，但成年人只在睪丸(testis)以及結腸(colon)中有表現。由microarray、RT-PCR及西方墨點法的實驗結果可知，有EGFR或EGFR mutant過量表現的H1299細胞株，其DUSP23的表現量會受到抑制。DUSP23會抑制EGF誘發的EGFR磷酸化，也會抑制Src的活性，然而在in vitro的去磷酸化實驗中均顯示pEGFR、pSrc皆不是DUSP23的受質。由研究DUSP23生物功能的實驗結果可知，DUSP23不會影響細胞的生長、移動，但是會影響細胞在三度空間的型態。此外亦發現，在不同非小細胞肺癌細胞株內，其DUPS23表現量和EGFR的表現量沒有相關性。綜合以上實驗結果可知，DUSP23是EGFR signaling pathway的負調控因子，但DUSP23是否經由抑制Src之活性進而抑制EGF誘發的EGFR磷酸化仍屬未知。

Dual-specificity phosphatases (DUSPs) have the ability to dephosphorylate both phosphotyrosine and phosphoserine/threonine residues. DUSPs are currently known to be involved in the negative regulation of MAPKs (mitogen-activated protein kinases) signaling pathway and cell cycle transitions. However, there are some small DUSPs whose functions remain unknown. Some DUSPs are called atypical DUSPs, because they contain only the consensus DUSP catalytic domain. DUSP23 contains 151 amino acids with molecular mass of 15~16 kDa, and it’s the smallest atypical DUSPs whose function is unknown. According to a previous, DUSP23 was expressed in most fetal tissues but in only testis and colon during adulthood. According to our microarray, RT-PCR, and Western blotting data, we showed that DUSP23 was transcriptionally inhibited when EGFR or mutant EGFR was overexpressed in H1299 non-small cell lung cancer cell line. Moreover, DUSP23 could reduce EGF-induced activation of EGFR and inhibit Src activity. Protein phosphatase assay showed that EGFR and Src were not direct substrates of DUSP23. As for functional assays, we found that DUSP23 could not alter cell growth and migration, but could affect cell morphology in a 3D culture model. And we found there is no significant correlation between the expression levels of EGFR and DUSP23 in several NSCLC cell lines. These results indicated that DUSP23 might be the negative regulator of EGFR signaling pathway in H1299. However, whether DUSP23 reduces EGF-induced activation of EGFR through the inhibition of Src activity is still under investigation.

中文摘要...........................................................................................................................1
英文摘要...........................................................................................................................2
序言...................................................................................................................................3
材料與方法.......................................................................................................................7
結果..................................................................................................................................23
討論..................................................................................................................................31
參考文獻..........................................................................................................................34
附圖………………………………………………...…………………………….…... ..39
附錄………………………………………………...………………………..……….. ..54

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