抗血管新生趨化素CXCL4及CXCL4L1其受體鍵結專一性及寡聚態研究

Receptor binding specificity and oligomerization status of anti-angiogenic chemokines, CXCL4 and CXCL4L1

吳欣勵(Wu, Hsin Li)

指導教授 ： 蘇士哲

國立清華大學/生命科學院/生物資訊與結構生物研究所/碩士(2016年)

摘要

趨化因子 (chemokine) 與其受體 (chemokine receptor) 之間的交互作用廣泛地參與發炎反應、血液凝集以及癌症轉移。大部分的趨化因子具有不同的寡聚態，而寡聚態的不同具有不同的生理意義。CXCL4 (PF4) 為最初被發現具有抑制血管新生活性的趨化因子，主要是透過CXCL4的受體¬－CXCR3來媒介CXCL4的抗血管新生活性。我們想更深入的了解不同的CXCL4寡聚態與CXCR3之間的調控機制，監測CXCR3的N端序列 (18-36) 與CXCL4的四聚體、二聚體以及單體之間的交互作用。我們利用pH值、氯化鈉濃度的不同以及突變的方式去調控CXCL4的寡聚態。藉由滴定CXCR3的N端胜肽到CXCL4，並且探討酪胺酸硫酸化 (tyrosine sulfation) 轉譯後修飾對趨化因子作用的重要性。酪胺酸硫酸化CXCR3胜肽對CXCL4的四聚體、二聚體及單體的作用範圍皆有所不同。
除此之外，我們也將注意集中在CXCL4L1，是CXCL4的變異蛋白，有三個殘基的不同，分別是P58L、K66E、L67H。CXCL4L1擁有比CXCL4更高的抗血管新生能力。CXCL4L1的C端螺旋結構在水溶液可能是個不穩定的結構。因為C端螺旋結構是穩定二聚體重要的角色，所以CXCL4L1比CXCL4更容易從四聚體分離成單體。我們認為不同的寡聚態與CXCL4跟CXCL4L1的抗血管新生活性相關。

關鍵字

趨化素 ； 寡聚態

並列摘要

Interactions of chemokines and chemokine receptors are extensively involved in blood coagulation, inflammatory and cancer metastasis. Most chemokines have distinct oligomerization states that are correlated with their biological functions. CXCL4 (PF4) is the first chemokine identified to be anti-angiogenic chemokine and its activity is mediated through its receptor CXCR3. To understand the detail mechanism of different CXCL4 oligomers in regulating CXCR3 function, we prepared CXCL4 monomer, dimer and tetramer and monitored the interaction with CXCR3 N-terminal sequence (residue 18-36). CXCL4 oligomer status was controlled by pH, NaCl concentration and mutation(s). By titrating the CXCR3 N-terminus-derived peptide into CXCL4 solutions, we characterized the critical role of post-translational modification of tyrosine sulfation for chemokine interaction. The sulfated CXCR3 N-terminus-derived peptide showed different extents in interacting CXCL4 monomer, dimer and tetramer. Furthermore, we focused on CXCL4L1, a CXCL4 variant that has three substitutions at P58L, K66E and L67H. CXCL4L1 possesses higher anti-angiogenetic activity than CXCL4. We revealed that CXCL4L1 contained a C-terminal helix with disordered property. Because of the role of C-terminal helix in stabilizing dimer interface, CXCL4L1 have greater ability to dissociate itself into monomer. We believe the different oligomer tendencies to change CXCL4 and CXCL4L1 anti-angiogensis activity.

並列關鍵字

CXCL4 ； CXCL4L1 ； chemokine ； oligomerization

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