Molecular Mechanism of production and secretion of platelet-derived bioactive lysolipids

近年来，人们发现了血清溶血磷脂介质的受体，如磷酸鞘磷脂（S1P）和溶血磷脂酸（LPA），它们在生理和病理生理方面的作用受到了广泛关注。这些生物活性脂质被观察到从活化的血小板中释放出来，但其产生、分泌和降解的详细机制尚未被深入研究。因此，在这个为期三年的日美研究项目中，我们试图在日本和美国团队的强有力合作下，阐明这些生物活性溶脂的产生、分泌和降解的分子机制。通过合作，我们尝试并发现了以下结果。(1)血中S1P主要来源于受刺激的血小板，LPA由受刺激的血小板部分释放，但主要由活化的血小板在溶血磷脂酶d的帮助下释放的磷脂酶在血液中产生。(2)我们从血磷脂中部分纯化了产生溶血磷脂的磷脂酶。(3)发现ABC转运蛋白参与血小板中S1P的释放，但我们无法确定具体参与的ABC转运蛋白。(4)首次鉴定出一种鞘脂转运蛋白RSB - 1，这是一种atp依赖性的新型六跨膜转运蛋白，可以排除酵母细胞中超载的DHS和PHS。(5)利用Edg-6 (S1P6)/S1P相互作用的计算模型确定了配体-受体相互作用的分子机制。通过这些合作研究，我们丰富了对血源性生物活性溶脂如LPA和S1P的代谢和功能调控的认识，表明了这些溶脂调节在血管生物学和病理学中的重要性。

The receptors for serum-borne lysophospholipid mediators such as sphingosine1-phosphate (S1P) and lysophosphatidic acid (LPA) was identified in these several years and their physiological and pathophysiological roles have been strongly concerned. These bioactive lipids were observed to be released from activated platelets, but the detailed mechanism of their production, secretion and degradation have not been thoroughly studied. Therefore, in this three years Japan-USA research project, we have tried to clarify the molecular mechanism of production, secretion, and degradation of these bioactive lysolipids in the strong collaboration between Japanese and American groups.Through the collaboration we tried and found the following results. (1) Blood S1P is derived mainly from stimulated platelets and LPA is partially released from stimulated platelets but mostly produced in the blood by phospholipases which are released from activated platelets with the aids of lysophospholipase D. (2) We partially purified the responsible phospholipases which produce the lysophospholipids from the blood phospholipids. (3) The involvement of ABC transporter in S1P releasing from platelets was found but we could not determine the specific ABC transporter involved. (4) We identified for the first time a sphingolipid transporter RSB 1, a ATP-dependent new type of six transmembrane transporter, which can exclude the over-loaded DHS and PHS from yeast cells (5) We determined the molecular mechanism of ligand-receptor interaction utilizing computational model of Edg-6 (S1P6)/S1P interaction.By these collaboration studies we enriched our knowledge how the metabolism and functions of the blood-borne bioactive lysolipids such as LPA and S1P are regulated, indicating the importance of the regulations of these lysolipids in blood vessel biology and pathology.