FUNCTION OF PLATELETS AND COAGULATION FACTORS

描述：(改编自申请者的摘要)这项资助的目标是阐明磷脂酰肌醇信号系统唤起细胞内对细胞外激动剂的反应的机制。了解这一系统将对血小板生理学和病理学以及巨核细胞的增殖和分化提供新的见解。这些实验还将解决几种疾病状态的发病机制，在这些疾病状态下，肌醇信号存在缺陷。特别是，申请者将研究血小板中肌醇多磷酸4-磷酸酶(4-Ptase)和磷脂酰肌醇3-激酶之间的关系。他将研究4-Ptase控制GATA-1缺失巨核细胞中巨核细胞增殖的机制。在缺乏4-Ptase的情况下，这些巨核细胞不断增殖，不能产生血小板。4-Ptase的恢复阻止了巨核细胞的生长。他将使用NIH3T3细胞来研究4-Ptase的这种生长抑制特性是否具有普遍性。他将研究4-Ptase，SopB的同源基因，这是一种沙门氏菌基因，是毒力所必需的。在没有SopB的情况下，这些微生物感染肠道上皮细胞，但不能诱导中性粒细胞渗入和腹泻。SopB是一种肌醇磷酸酶，是毒力所必需的酶活性。感染细胞中肌醇代谢的底物特异性和紊乱将被确定。他将研究4-Ptase的另一个同源物，这是一种肿瘤抑制基因(PTEN)，也是一种肌醇磷酸酶。OCRL-1 5-磷酸酶，当突变时是洛威综合征的原因，将被检查。申请人提出，该缺陷导致了Lowe综合征中溶酶体酶的异常靶向性。他计划对此进行研究，并测量洛威综合征患者的血浆溶酶体酶。他还将试图阐明四磷酸肌醇和五磷酸肌醇异构体的酶学和生产调控。他将鉴定、分离和克隆导致InsP5的酶的cDNA，首先是肌醇1，3，4-三磷酸5/6-激酶。

DESCRIPTION: (Adapted from the Applicant's Abstract) This grant has as its goal the elucidation of the mechanisms by which the phosphatidylinositol signalling system evokes intracellular responses to extracellular agonists. Understanding this system will provide new insights into platelet physiology and pathology and also into the proliferation and differentiation of megakaryocytes. The experiements will also address the pathogenesis of several disease states in which defects in inositol signalling are present. In particular, the applicant will study the relationship between inositol polyphosphate 4-phosphatase (4-Ptase) and phosphatidylinositol 3-kinase in platelets. He will investigate the mechanism by which 4-Ptase controls megakaryocyte proliferation in GATA-1 null megakaryocytes. In the absence of 4-Ptase, these megakaryocytes proliferate continuously and fail to produce platelets. Restoration of 4-Ptase arrests megakaryocyte growth. He will use NIH 3T3 cells to investigate whether this growth arresting property of 4-Ptase is general. He will investigate the homolog of 4-Ptase, SopB, a Salmonella gene required for virulence. In the absence of SopB, the organisms infect intestinal epithelia but fail to induce neutrophilic infiltration and diarrhea. SopB is an inositol phosphatase and enzyme activity is required for virulence. The substrate specificity and derangement of inositol metabolism in infected cells will be determined. He will study another homolog of 4-Ptase that is a tumor suppressor gene (PTEN) and is also an inositol phosphatase. The OCRL-1 5-phosphatase that when mutated is the cause of Lowe Syndrome will be examined. The applicant propose that the defect results in abnormal targeting of lysosomal enzyme in Lowe Syndrome. He plans to study this and to measure plasma lysosomal enzymes in patients with Lowe Syndrome. He will also attempt to elucidate the enzymology and regulation of production of isomers of inositol tetraphosphates and inositol pentaphosphates. He will identify, isolate, and clone cDNA for enzymes leading to InsP5 starting with inositol 1,3,4-triphosphate 5/6-kinase.