Reduction of Atherogenesis in the Knock-out Mice of Tyrosine Kinase PYK2 which plays Essential Role in Cell Migration and Cytokine Induction

PYK2是一种在细胞迁移和细胞因子诱导中起关键作用的酪氨酸激酶。同时，这些细胞功能对动脉粥样硬化的形成至关重要。因此，我们探讨了PYK2在动脉粥样硬化形成中的功能作用。我们采用载脂蛋白E缺陷小鼠作为模型小鼠。我们对ApoE基因敲除小鼠和ApoE、PYK2双基因敲除小鼠的动脉粥样硬化区域进行了组织学上的比较。PYK2、ApoE双基因敲除小鼠动脉粥样硬化区面积明显小于ApoE缺陷小鼠，这是由于ApoE基因敲除小鼠动脉粥样硬化区内单核细胞数量减少所致。ApoE、PYK2双基因敲除小鼠动脉粥样硬化区IL-1β和TNFα的诱生以及血管内皮细胞表面VCAM的表达和PAI-1的产生均明显低于ApoE基因敲除小鼠。此外，ApoE缺陷小鼠动脉粥样硬化区内皮细胞上的PYK2被强烈的酪氨酸磷酸化。ApoE基因敲除小鼠动脉粥样硬化区Src酪氨酸磷酸化水平或总酪氨酸磷酸化蛋白含量显著增加，而ApoE、PYK2双基因敲除小鼠动脉粥样硬化区Src酪氨酸磷酸化水平和总酪氨酸磷酸化蛋白含量显著降低。此外，与ApoE基因敲除小鼠相比，ApoE、PYK2双基因敲除小鼠内皮细胞上细胞周期调节蛋白p16或p21的表达显著减少。综上所述，与ApoE缺陷小鼠相比，PYK2缺陷小鼠的细胞迁移受损和单核细胞细胞因子产生的改变导致PYK2和ApoE缺陷小鼠动脉粥样硬化的严重程度减轻。因此，这些实验首次揭示了PYK2在动脉粥样硬化形成中的重要作用。

PYK2 is the tyrosine kinase that play critical role in cell migration and cytokine induction. Meanwhile, these cell functions is critical for atherogenesis. We therefore pursued the functional role of PYK2 in atherogenesis. We adopted ApoE deficient mice as model mice. We histologically compared atherosclerotic region of ApoE knockout mice with that of ApoE, PYK2 double knockout mice, which were fed with high fat diet. The area of atherosclerotic region in PYK2, ApoE double knockout mice was much smaller than that in ApoE deficient mice, which was caused by decrease in the number of infiltrating monocytes into atherosclerotic region. Also, induction of IL-1beta or TNFalpha as well as expression of VCAM on endothelial cells or production of PAI-1 in the atherosclerotic region of ApoE, PYK2 double knockout mice was much reduced than that of the ApoE knockout mice. Further, PYK2 on endothelial cells in the atherosclerotic region of ApoE deficient mice was strongly tyrosine-phosphorylated. Tyrosine phosphorylation of Src or the amount of total tyrosine phosphorylated protein were significantly increased in the atherosclerotic region of ApoE knockout mice, whereas their increase was dramatically abolished in the atherosclerotic region of ApoE, PYK2 double knockout mice. Moreover, expression of the cell cycle regulatory proteins, p16 or p21, on the endothelial cells of ApoE, PYK2 double knockout mice was significantly reduced in comparison to that of ApoE knockout mice. Taken together, the impaired cell migration and altered cytokine production of monocyte in PYK2 deficient mice leads to reduced severity of atherosclegenesis in PYK2, ApoE deficient mice in comparison to ApoE deficient mice. Thus, these experimnt revealed at the first time that PYK2 plays critical role in atherogenesis.