乳癌激酶之訊息傳遞暨其受Hsp90與泛素化之調控

Signaling Transducation of Brk and Its Regulation by Hsp90 in Concert with Ubiquitination

黃元平(Yuan-Ping Huang)

指導教授 ： 陳瑞華

國立臺灣大學/醫學院/分子醫學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00845

摘要

乳癌激酶(Breast tumor kinase, Brk)是屬於Src-like酪氨酸激酶家族中的一員，在大部分惡性乳癌細胞株中都有大量表現。先前的研究已證實乳癌激酶的表現與乳癌病灶的進程有很大的關係，然而乳癌激酶促進癌症發展的分子機制至今仍不是十分清楚。在本篇論文中，我們發現了Paxillin是乳癌激酶的一個新受質。在細胞內乳癌激酶的表現會促進Paxillin 的酪氨酸磷酸化，而且乳癌激酶和Paxillin在細胞內會彼此結合。此外，我們也證實了Paxillin的N端LD區域以及C端LIM區塊均可以直接和乳癌激酶相互作用。我們同時也發現了乳癌激酶會和Hsp90互相結合。以Geldanamycin抑制Hsp90的活性會造成乳癌激酶的泛素化(ubiquitination)增加，這個現象在我們使用乳癌激酶的永久活化突變型(BrkY447F)時更加明顯，表示活化的乳癌激酶會受到Hsp90的保護而免於受到 泛素化而降解。我們接著也證實了CHIP 可能是造成乳癌激酶在Hsp90被抑制下泛素化上升的ubiquitin ligase。另外，我們發現表皮生長激素(EGF)會經由活化一種ubiquitin ligase Cbl促進乳癌激酶的泛素化進而激化乳癌激酶的蛋白質降解。我們的實驗結果顯示乳癌激酶的訊息傳遞不僅受到Hsp90的保護，同時受到Cbl及CHIP造成之乳癌激酶泛素化的負向調控。

關鍵字

乳癌激酶泛素化 ； 訊息傳遞

並列摘要

Breast tumor kinase (Brk) is a Src-like family non-receptor tyrosine kinase over-expressed in most breast cancer cells. Previous studies have established the correlation of Brk expression and the progression of malignancy. However, the exact biological function of Brk and the molecular mechanism through which Brk contributes to tumor metastasis remain to be elucidated. In this thesis, we have identified Paxillin as a novel cytosolic substrate of Brk. Expression of Brk significantly enhanced tyrosine phosphorylation of Paxillin, and these two proteins interacted with each other in vivo. We also showed that both N-terminal LD region and C-terminal LIM domain of Paxillin could mediate interaction with Brk. Besides, we found Hsp90 interacts with Brk in vivo. Subsequent experiments demonstrated that active Brk is under the protection of Hsp90 that its inactivation by treatment of geldanamycin (GA) results in ubiquitination of Brk mediated by the ubiquitin ligase C-terminus of Hsc70 interacting protein (CHIP). Moreover, we found that EGF treatment stimulated protein turnover of Brk through ubiquitination catalyzing by the ubiquitin ligase Cbl that is activated in response to EGF signal. These data suggested signaling of Brk is escorted by Hsp90 and negatively regulated by Cbl/CHIP-mediated ubiquitination.

並列關鍵字

Brk ； Hsp90 ； Ubiqitination

參考文獻

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