FUNCTION OF PLATELETS AND COAGULATION FACTORS

描述：（改编自申请人摘要）本基金的目标是阐明磷脂酰肌醇信号系统对细胞外激动剂引起细胞内反应的机制。了解这个系统将为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。实验还将解决几种疾病状态的发病机制，其中肌醇信号缺陷是存在的。特别是，申请人将研究血小板中肌醇多磷酸4-磷酸酶（4-Ptase）与磷脂酰肌醇3-激酶之间的关系。他将研究4-Ptase在GATA-1无巨核细胞中控制巨核细胞增殖的机制。在缺乏4-Ptase的情况下，这些巨核细胞持续增殖，不能产生血小板。4- pase的恢复可以抑制巨核细胞的生长。他将使用NIH 3T3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）的同源性，SopB是沙门氏菌毒性所需的一种基因。在缺乏SopB的情况下，微生物感染肠上皮，但不能诱导中性粒细胞浸润和腹泻。SopB是一种肌醇磷酸酶，它的活性是产生毒力所必需的。将确定感染细胞中肌醇代谢的底物特异性和紊乱。他将研究4-Ptase的另一个同源物，它是一种肿瘤抑制基因（PTEN），也是一种肌醇磷酸酶。当OCRL-1 5-磷酸酶发生突变时，将被检查为Lowe综合征的原因。申请人认为该缺陷导致Lowe综合征溶酶体酶靶向异常。他计划对此进行研究，并测量劳氏综合征患者的血浆溶酶体酶。他还将尝试阐明四磷酸肌醇和五磷酸肌醇异构体生产的酶学和调控。他将从肌醇1,3,4-三磷酸5/6激酶开始，鉴定、分离和克隆导致InsP5的酶的cDNA。

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.