Phospholipase Cε links G protein-coupled receptor activation to inflammatory astrocytic responses
Phospholipase Cε links G protein-coupled receptor activation to inflammatory astrocytic responses
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DOI：
10.1073/pnas.1217355110
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发表时间：
2013-02-26
影响因子：
11.1
通讯作者：
Brown, Joan Heller
中科院分区：
文献类型：
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作者：
Dusaban, Stephanie S.;Purcell, Nicole H.;Brown, Joan Heller
神经炎症在中枢神经系统疾病的病理生理学中起着重要作用，星形胶质细胞在这一过程中的作用越来越受到人们的重视。凝血酶和溶血磷脂溶血磷脂酸和鞘氨醇1-磷酸(S1P)是在损伤过程中产生的，可以激活星形胶质细胞上的G蛋白偶联受体(GPCRs)。我们推测，与RAS同源基因家族成员A(RhoA)偶联的GPCRs通过小GTP酶反应磷脂酶epsilon(PLC Epsilon)诱导星形胶质细胞炎症基因表达。利用野生型和PLC epsilon基因敲除小鼠的原代星形胶质细胞，我们证明了凝血酶或SIP处理1小时后，环氧合酶2(COX-2)的mRNA水平增加了10倍，这需要PLC epsilon。IL-6和IL-1β的mRNA水平也以PLC epsilon依赖的方式增加。凝血酶、溶血磷脂酸和S1P通过RhoA、催化活性的PLC epsilon、蛋白激酶D(PKD)的持续激活和NF-kappa B的核转位等机制促进COX-2蛋白的表达，体外损伤实验中从星形胶质细胞释放的内源性配体也通过PLC epsilon和NF-kappa B依赖的途径诱导COX-2的表达。此外，体内刺伤可在WT中激活PKD并诱导COX-2等炎症基因，但在PLC epsilon基因敲除的小鼠脑中不能。因此，PLC epsilon将GPCRs与持续的PKD激活联系在一起，为连接到RhoA的GPCR配体提供了一种手段，以诱导NF-kappa B信号转导和促进神经炎症。
Neuroinflammation plays a major role in the pathophysiology of diseases of the central nervous system, and the role of astroglial cells in this process is increasingly recognized. Thrombin and the lysophospholipids lysophosphatidic acid and sphingosine 1-phos-phate (S1P) are generated during injury and can activate G protein-coupled receptors (GPCRs) on astrocytes. We postulated that GPCRs that couple to Ras homolog gene family, member A (RhoA) induce inflammatory gene expression in astrocytes through the small GTPase responsive phospholipase epsilon (PLC epsilon). Using primary astrocytes from wild-type and PLC epsilon knockout mice, we demonstrate that 1-h treatment with thrombin or SIP increases cyclooxygenase 2 (COX-2) mRNA levels similar to 10-fold and that this requires PLC epsilon. Interleukin-6 and interleukin-1 beta mRNA levels are also increased in a PLC epsilon-dependent manner. Thrombin, lysophosphatidic acid, and S1P increase COX-2 protein expression through a mechanism involving RhoA, catalytically active PLC epsilon, sustained activation of protein kinase D (PKD), and nuclear translocation of NF-kappa B. Endogenous ligands that are released from astrocytes in an in vitro wounding assay also induce COX-2 expression through a PLC epsilon- and NF-kappa B-dependent pathway. Additionally, in vivo stab wound injury activates PKD and induces COX-2 and other inflammatory genes in WT but not in PLC epsilon knockout mouse brain. Thus, PLC epsilon links GPCRs to sustained PKD activation, providing a means for GPCR ligands that couple to RhoA to induce NF-kappa B signaling and promote neuroinflammation.