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標題: Focal Adhesion Kinase在致癌基因Tpr-Met所引起細胞轉型過程中所扮演的角色
Role of Focal Adhesion Kinase in Oncogene Tpr-Met-stimulated Cell Transformation
作者: 陳淑怡
Yi, Chen Shu
關鍵字: FAK;FAK;Tpr-Met;oncogene;phosphorylation;tumor;transformation;Tpr-Met;致癌基因;磷酸化;腫瘤;細胞轉型
出版社: 生命科學系
Focal adhesion kinase(FAK)是一種細胞質內存在於focal contacts的酪氨酸磷酸化激酶,其分子量為125 kDa,目前被認為在integrin所調控的細胞功能中扮演一個關鍵性的角色。最近我們也發現,FAK的過量表現可與肝細胞生長因子的刺激產生協同作用,共同造成細胞的腫瘤化(Chan et al., 2002, J. Biol. Chem. 277, 50373-50379)。c-met是一種原致癌基因,其蛋白產物為肝細胞生長因子接受體,透過染色體轉位可產生具致癌性融合基因tpr-met。Tpr-Met是一種細胞質內分子量約為65 kDa的酪氨酸磷酸化激酶,其kinase是持續處於活化狀態,並且本身的酪氨酸呈現被磷酸化狀態。在本研究中,主要是探討Tpr-Met與FAK之間的作用。實驗結果顯示,細胞內Tpr-Met的表現會引起FAK酪氨酸磷酸化的上升,在in vitro Tpr-Met可以直接將FAK磷酸化。此外Tpr-Met可以直接地與FAK形成穩定的複合物,當Tpr-Met的Tyr-482和Tyr-489突變後則會減弱原本Tpr-Met與FAK的結合,並且也降低對FAK磷酸化的能力。我們也發現單獨FAK的N端或C端就可以與Tpr-Met形成穩定的複合物。更進一步探討FAK在Tpr-Met所引起細胞轉型上的影響,發現同時表現Tpr-Met和FAK蛋白會促進細胞anchorage-independent生長能力和侵犯能力,並且其侵犯能力與matrix metalloprotease-2活性和表現量的增加有關。生化的結果顯示FAK的存在對於Tpr-Met活化ERK、JNK、c-Jun 、AKT是重要的,但不增強原本Tpr-Met對STAT-3磷酸化的能力。綜合上述結果,FAK可能是Tpr-Met在增大下游訊號中的一個平臺,並且在Tpr-Met所引起的細胞轉型中扮演一個重要的角色。

Keywords: FAK, Tpr-Met, oncogene, phosphorylation, tumor, transformation
Focal adhesion kinase (FAK), a 125 kDa cytoplasmic protein tyrosine kinase localized in focal contacts, plays a crucial role in the control of integrin- mediated cellular functions. We have previously demonstrated that increased expression of FAK renders epithelial cells susceptible to transformation by hepatocyte growth factor (HGF) stimulation (Chan et al., 2002, J. Biol. Chem. 277, 50373-50379). The HGF receptor is encoded by the proto-oncogene c-met, which can be uncongenially activated through a chromosomal rearrangement that creates a hybrid gene tpr-met. Tpr-Met, a 65 kDa protein tyrosine kinase which is constitutively active and phosphorylated on tyrosine residues. In this study, I attempted to examine the potential interaction between FAK and Tpr-Met. My results showed that Tpr-Met stimulates the tyrosine phosphorylation of FAK in intact cells and is capable of directly phosphorylating recombinant FAK in vitro. Moreover, I demonstrated that Tpr-Met is associated with FAK both in vivo and in vitro. Mutations at the Tyr-482 and Tyr-489 of Tpr-Met impair the ability of Tpr-Met to bind and phosphorylate FAK. The NH2- and COOH-terminal domains of FAK are sufficient for Tpr-Met binding in vivo and in vitro. My results showed that the expression of FAK enhances Tpr-Met induced anchorage-independent cell growth and cell invasiveness. The ability of these cells to invade Matrigel correlated with activation and increased expression of matrix metalloprotease-2. Biochemical analysis revealed that FAK is important for Tpr-Met-induced activation of ERK, JNK, c-Jun, and AKT, but not STAT-3. Together, FAK may serve as a platform for Tpr-Met to amplify the signals to the downstream and play an important role in Tpr-Met-induced cell transformation.
Appears in Collections:生命科學系所

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