Regulation of distribution of extracellular Edg receptor family ligands and their physiological roles

我们研究了细胞外鞘氨醇1-磷酸(S1P)和溶血磷脂酸(LPA)的分布规律及其生理作用。(1)S1P作为脂蛋白在血管细胞中作用的中介：我们发现高密度脂蛋白-S1P与高密度脂蛋白-胆固醇有很好的相关性。为了确定参与血管内皮细胞高密度脂蛋白和S1P作用的受体亚型，我们利用反义寡核苷酸或siRNA特异性S1P受体亚型，证明细胞存活主要由S1P1介导，细胞迁移主要由S1P1和S1P3共同介导，抑制肿瘤坏死因子-α诱导的黏附分子表达主要通过S1P1。在血管平滑肌细胞中，S1P2受体介导cAMP积聚和抑制细胞迁移。这些结果表明，S1P受体是治疗血管疾病的有用靶点。(2)LPA受体拮抗剂的性质及其应用：我们将Ki16425鉴定为LPA受体拮抗剂，结果表明该药物对胰腺癌细胞、胶质瘤细胞等癌细胞的运动有抑制作用。(3)脂质介质在中枢神经系统中的作用：我们发现脑脊液中的自体趋化因子是一种溶血磷脂酶D，是轴突收缩因子。(4)溶脂受体的一个新功能：我们证明TDAG8是一种脂类分子精神素的受体，它能感觉细胞外的质子或pH，从而导致腺苷环化酶的激活。我们还利用siRNA技术证明了细胞外酸性pH通过OGR1诱导人血管SMC产生前列腺素和cAMP积累。OGR1是一种与TDAG8具有相似一级结构的GPCRs。因此，OGR1家族GPCRs是感受胞外pH的功能性受体。

We examined the regulation of distribution of extracellular sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA), and their physiological roles. (1) S1P as a mediator of lipoprotein actions in vascular cells : We showed a good correlation between HDL-S1P and HDL-cholesterol. In order to identify the receptor subtypes involved in HDL and S1P actions in vascular endothelial cells, we used antis enseoligonucleotides or siRNA specific S1P receptor subtypes and demonstrated that cell survival is mainly mediated by S1P1, cell migration is by both S1P1 and S1P3, and inhibition of TNF-α-induced adhesion molecule expression is by mainly S1P1. In vascular smooth muscle cells, it was shown that S1P2 receptor mediates cAMP accumulation and inhibition of cell migration. These results suggest that S1P receptors are useful therapeutic targets for vascular diseases. (2) Characterization of an LPA receptor antagonist and its application : We characterized Ki16425 as an LPA receptor antagonist and showed that this drug is effective for inhibiting motility of cancer cells such as pancreatic cancer cells and glioma cells. (3) Role of lipid mediator in central nervous system : We identified autotaxin, a lysophospholipase D, as a neurite retraction factor in cerebrospinal fluid. (4) A novel function of lysolipid receptors : We demonstrated that TDAG8, which has been shown to be a receptor for lipid molecule psychosine, senses extracellular proton or pH, resulting in activation of adenylyl cyclase. We also demonstrated by using siRNA techniques that extracellular acidic pH induces prostaglandin production and cAMP accumulation through OGR1, one of GPCRs with a similar primary structure to TDAG8, in human vascular SMC. Thus, OGR1 family GPCRs are functional receptors for sensing extracellular pH.