中文摘要：

磷脂酶Cβ（PLCβ）在G蛋白偶联受体（GPCR）介导的细胞信号转导中发挥重要作用.通过水解磷脂酰肌醇4,5二磷酸（PIP2）,磷脂酶Cβ可以产生3种重要的第二信使分子：二乙酰甘油（DAG）、三磷酸肌醇（IP3）和质子.在果蝇中,磷脂酶Cβ通过它的羧基末端盘状同源区域结合模块（PBM）与盘状同源区域（PDZ）支架蛋白—失活无后电位D蛋白（INAD）相互作用,从而调节果蝇的光信号传导.在哺乳动物中,磷脂酶Cβ家族有4个亚型,每1个亚型的羧基末端都有1个典型的盘状同源区域结合模块.这一结构特点提示我们,磷脂酶Cβ可能通过其羧基末端的盘状同源区域结合模块与盘状同源区域支架蛋白相互作用,进而调节它们自身的细胞定位和功能.然而,目前仍对哺乳动物磷脂酶Cβ家族的盘状同源区域结合蛋白知之甚少.本文运用分析型凝胶过滤和等温滴定量热技术,系统地研究了不同磷脂酶Cβ亚型的羧基末端盘状同源区域结合模块与不同盘状同源区域蛋白质的结合.结果表明,磷脂酶Cβ2的羧基末端盘状同源区域结合模块,可以特异地与含有4个盘状同源区域的支架蛋白—盘状同源区域蛋白1（PDZK1）以2∶1的方式相互结合.进一步的测定显示,磷脂酶Cβ2羧基末端盘状同源区域结合模块在盘状同源区域蛋白1上的结合位点为第1和第3个盘状同源区域,而它们与磷脂酶Cβ2的解离常数分别为11.8±3.4μmol/L和33.3±8.7μmol/L.

英文摘要：

Phospholipase C β（ PLCβ） plays important roles in G-protein-coupled receptor（ GPCR）mediated signal transduction cascade. By hydrolyzing phosphatidylinositol-4,5-bisphosphate（ PIP2）,three important second messengers are generated,which are diacylglycerol（ DAG）,inositol-1,4,5-triphosphate（ IP3） and proton. In Drosophila,PLCβ interacts with a PDZ containing scaffold protein called Inactivation-no-afterpotential D（ INAD） via its C-terminal PDZ binding motif（ PBM） to mediate the phototransduction process. In mammals,there are four isoforms in PLCβ family,and each of them has a classic PBM at their very C termini,indicating they may interact with PDZ scaffold proteins,helping them to execute their functions in different parts of the cell. However,their PDZ binding partners are still largely unknown. In this study,by using the analytical gel-filtration and isothermal titration calorimetry（ ITC） techniques,we systematically tested the interactions between different PDZ containing proteins and PLCβ isoforms. We uncovered that the PLCβ2 C-terminal PBM specifically interacted with a four PDZ domain containing scaffold protein called PDZ domain containing 1（ PDZK1） in 2 ∶ 1 ratio.Further mapping showed that the PLCβ2 C-terminal PBM bound to the first and the third PDZ domains of PDZK1,and their binding affinities were 11. 8 ± 3. 4 μmol /L and 33. 3 ± 8. 7 μmol /L,respectively.