Structure and Functions of CD38

CD38的结构和功能

基本信息

批准号：
7579044
负责人：
RICHARD M GRAEFF
金额：
$ 41.92万
依托单位：
UNIVERSITY OF MINNESOTA
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-06-01 至 2010-10-31
项目状态：
已结题

项目摘要

It is generally believed that multiple Ca2+ stores are present in cells, a notion that has now been made substantive by the discovery of multiple Ca2+ mobilizing messengers. Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are two such messengers that are derived from NAD and NADP, respectively. A wide variety of cells, from plants to mammals, including human, have been shown to be responsive to these two novel Ca2+ messengers. Not only are their structures and mechanisms of action different, their targeted Ca2+ stores are also distinct and separable. Moreover, they are derived from different substrates, cADPR from NAD and NAADP from NADP. It is thus entirely unexpected that a single enzyme is responsible for synthesizing these two different Ca2+-messengers. CD38 is one such enzyme and it belongs to a new family of homologues that includes CD157 and Aplysia ADP-ribosyl cyclase. Results using knockout mice show that CD38 is the most dominant enzyme in mammalian tissues responsible synthesizing cADPR and NAADP. The emerging view is that cADPR and NAADP represent two branches of a novel Ca2+-signaling pathway with CD38 at its bifurcation point. Because of its pivotal role in the cADPR/NAADP-signaling pathway, it is of critical importance that the molecular mechanism of its action be elucidated. We have expressed the extra-membrane domain of CD38 in yeast as a soluble protein that retains all enzymatic activities indistinguishable from native CD38. We have mapped the active site and identified the critical residues in it by site-directed mutagenesis. These results form the basis for a unified catalytic model that accounts for the novel multiplicity of this family of signaling enzymes. We have now succeeded in crystallizing CD38 and solved its structure. The structure-function studies described in this proposal will verify and refine the catalytic model and the specific aims are: Aim 1: To determine the structural basis of the multi-catalytic functions of CD38. Aim 2: To determine the structural basis of regulation of CD38 catalysis. Aim 3: To determine the structural basis of the antigenic functions of CD38. Aim 4: To characterize intracellular CD38.

通常认为，单元格中存在多个Ca2+存储，这是现已提出的概念通过发现多个CA2+动员信使的实质性。循环ADP-ribose（CADPR）和烟酸腺嘌呤二核苷酸磷酸盐（NAADP）是两个来自NAD的使者和NADP。从植物到包括人在内的植物到包括人类的各种细胞已经证明对这两个新型CA2+信使有响应。他们的结构和机制不仅不同的动作，其目标CA2+存储也是不同的且可分开的。而且，它们源自不同的底物，NAD的CADPR，NADP的NAADP。因此，一个完全出乎意料的是酶负责综合这两个不同的Ca2+messengers。 CD38是一种这样的酶，它属于包括CD157和Aplysia ADP-核糖基环化酶在内的新型同源物系列。结果使用敲除小鼠表明CD38是负责的哺乳动物组织中最主要的酶综合CADPR和NAADP。新兴观点是CADPR和NAADP代表了两个分支一种新型的Ca2+ - 信号途径，其分叉点具有CD38。因为它在 CADPR/NAADP信号途径，其作用的分子机制至关重要阐明。我们已经表达了酵母中CD38的外膜外域，作为一种可溶性蛋白保留与本机CD38无法区分的所有酶活性。我们已经绘制了活跃的站点，通过定点诱变确定了其中的临界残基。这些结果构成了统一的基础催化模型解释了这种信号酶家族的新颖性。我们现在有成功地结晶了CD38并解决了其结构。在此描述的结构功能研究建议将验证和完善催化模型，具体目的是：目标1：确定CD38多催化功能的结构基础。目标2：确定CD38催化调节的结构基础。目标3：确定CD38抗原功能的结构基础。目标4：表征细胞内CD38。