CHARACTERIZATION OF A NOVEL CALCIUM STORE

细胞内Ca2+储存的动员由两种主要机制介导，即肌醇三磷酸（IP3）途径和Ca2+诱导的Ca2+释放（CICR）机制。我们的研究表明，Ca2+储存也可以通过两个新的信使通过完全独立的途径动员。环adp核糖（cADPR）和烟酸腺嘌呤二核苷酸磷酸（NAADP）分别是NAD和NADP的新代谢产物。越来越多的证据表明，cADPR是通过CICR作用的一般Ca2+信使。NAADP介导的Ca2+信号传导机制直到最近才被表征。对NAADP敏感的Ca2+存储与对IP3和cADPR敏感的Ca2+存储是可分离的。NAADP激活的Ca2+释放机制也完全独立于cADPR和IP3激活的Ca2+释放机制。然而，NAADP与cADPR是相关的，因为它们是由相同的酶合成的，但在不同的条件下。阐明这一迄今未知的由NAADP介导的信号通路可能对我们对信号转导机制的理解产生重要影响。具体目标是：1.；合成NAADP类似物。2. 建立内源性NAADP的检测方法。3. 表征naadp敏感Ca2+储存的亚细胞分布。4. 对naadp敏感的Ca2+储存进行生物化学表征。5. 确定naadp敏感Ca2+存储在Ca2+波传播中的作用。

Mobilization of intracellular Ca2+ stores is mediated by two major mechanisms, the inositol trisphosphate (IP3)-pathway and the Ca2+-induced Ca2+ release (CICR) mechanism. Our research establishes that Ca2+ stores can also be mobilized by two new messengers via totally independent pathways. Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are novel metabolites of NAD and NADP, respectively. Accumulating evidence indicates cADPR is a general Ca2+ messenger acting via the CICR. The Ca2+ signaling mechanism mediated by NAADP has only recently been characterized. The Ca2+ stores that are sensitive to NAADP are separable from those sensitive to IP3 and cADPR. The Ca2+ release mechanism activated by NAADP is also completely independent of those activated by cADPR and IP3. Nevertheless, NAADP is related to cADPR since both are synthesized by the same enzymes but under different conditions. Elucidation of this hitherto unknown signaling pathway mediated by NAADP is likely to have an important impact on our understanding of signal transduction mechanisms. Specific aims are: 1. To synthesize analogs of NAADP. 2. To develop assays for endogenous NAADP. 3. To characterize the subcellular distribution of the NAADP-sensitive Ca2+ stores. 4. To characterize the NAADP-sensitive Ca2+ stores biochemically. 5. To determine the role of the NAADP-sensitive Ca2+ stores in propagation of Ca2+ waves.