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

近年来，血清溶血磷脂介质如1-磷酸鞘氨醇（S1 P）和溶血磷脂酸（LPA）的受体被发现，其生理和病理生理作用受到人们的关注。这些生物活性脂质被观察到从活化的血小板中释放，但其产生、分泌和降解的详细机制尚未被彻底研究。因此，在为期三年的日美研究项目中，我们通过日美研究小组的密切合作，试图阐明这些生物活性溶磷脂的产生、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)血液S1 P主要来源于刺激的血小板，LPA部分从刺激的血小板释放，但主要通过磷脂酶在血液中产生，磷脂酶在溶血磷脂酶D的帮助下从活化的血小板释放。(2)我们部分纯化了从血磷脂中产生溶血磷脂的磷脂酶。(3)ABC转运蛋白参与了血小板释放S1 P的过程，但我们不能确定具体参与的ABC转运蛋白。(4)我们首次鉴定了鞘脂转运蛋白RSB 1，一种ATP依赖的新型六跨膜转运蛋白，（5）利用Edg-6（S1 P6）/S1 P相互作用的计算模型，我们确定了配体-受体相互作用的分子机制，通过这些合作研究，我们丰富了我们对血液代谢和功能的认识。例如LPA和S1 P的生物活性溶脂受到调节，表明这些溶脂的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.