Regulation of Cellular Functions by Cyclic Nucleotide Phosphodiesterase 8

描述（由申请人提供）：众所周知，cAMP在许多不同细胞的发育和功能中具有重要的多种调节作用。还已知cAMP主要通过激活cAMP依赖性蛋白激酶和/或鸟嘌呤核苷酸交换蛋白Epac起作用。此外，在过去的几年中，已经清楚的是，特定的隔室存在于大多数细胞中，用于组织和调节细胞中特定的cAMP依赖性过程。这种调节发生的最重要的机制之一是通过选择性激活或抑制细胞中环核苷酸磷酸二酯酶（PDE）的不同同工酶。尽管已知超过100种不同的PDE，但任何单个细胞类型通常表达不到六种PDE，任何单个隔室甚至更少。我们目前的理解是，非常少量的PDE将用于控制特定的cAMP或cGMP池。因此，不同的PDE可以很容易地调节细胞中的不同过程。所提出的研究的目标是在几种不同的细胞类型中鉴定该细胞中哪些过程和蛋白质受PDE 8A和PDE 8B调节。PDE 8家族是相对新发现的PDE家族，其对cAMP具有特异性，并且具有对异丁基甲基黄嘌呤（IBMX）完全不敏感的不寻常性质，IBMX是该类所有其他PDE的高效小分子抑制剂。因此，PDE 8直到最近才被认为是细胞功能的主要调节因子。然而，我们小组最近的数据表明，它们对细胞功能的调节非常重要。我们的新数据表明，除了Leydig细胞，PDE 8在肝细胞、棕色脂肪细胞和肾上腺束状细胞中高度表达。由于我们现在有PDE 8A和PDE 8B基因被破坏的小鼠，我们可以确定这两种PDE对细胞功能的重要性，尽管选择性小分子抑制剂还不可用。因此，我们建议，以确定在这些细胞类型中的每一个已知的cAMP调制的几个功能是由这个PDE家族，以及他们如何做到这一点。 公共卫生相关性：拟议的研究将探讨一个新发现的和以前未研究的环核苷酸磷酸二酯酶家族，PDE 8对肾上腺，肝脏和棕色脂肪功能的作用。初步证据表明，这些PDE是这些细胞类型中cAMP控制功能的主要调节剂。预计拟议的研究将告诉我们哪些过程受到调节以及调节如何在分子水平上发生。正如PDE的另一种特定形式是药物伟哥的靶点一样，一旦我们了解PDE 8在这些组织中的功能，它们也很可能成为治疗肾上腺，肝脏和脂肪组织功能障碍的药物的靶点。

DESCRIPTION (provided by applicant): It is well recognized that cAMP has important and multiple regulatory roles in the development and function of many different cells. It is also known that cAMP, works largely through activation of cAMP-dependent protein kinases and/or the guanine nucleotide exchange protein, Epac. Moreover, in the last few years it has become clear that specific compartments are present in most cells that serve to organize and regulate specific cAMP-dependent processes in the cells. One of the most important mechanisms by which this regulation occurs is through selective activation or inhibition of distinct isozymes of cyclic nucleotide phosphodiesterases (PDEs) in the cell. Although over 100 different PDEs are known, any single cell type usually expresses less than half a dozen of them and any single compartment even fewer. Our current understanding is that a very small number of PDEs will serve to control a particular pool of cAMP or cGMP. Therefore, different PDEs can easily regulate different processes in the cell. It is the goal of the proposed studies to identify in several different cell types which processes and proteins in that cell are regulated by PDE8A and PDE8B. The PDE8 family is a relatively newly discovered PDE family that is specific for cAMP and has the unusual property of being completely insensitive to isobutylmethylxanthine (IBMX), a highly effective small molecule inhibitor of all other PDEs of this class. As a result PDE8s have until recently not been implicated as major regulators of cellular function. However, recent data from our group now show that they can be very important to regulation of cell function. Our new data shows that in addition to Leydig cells, PDE8s are highly expressed in liver hepatocytes, brown fat cells, and adrenal fasciculata cells. Since we now have available mice having the PDE8A and PDE8B genes disrupted, we are in position to determine the importance of these two PDEs to cellular function, despite the fact that selective small molecule inhibitors are not yet available. Therefore, we propose to determine which of the several functions known to be modulated by cAMP in each of these cell types are regulated by this PDE family and how they do so. PUBLIC HEALTH RELEVANCE: The proposed studies will explore the role of a newly discovered and previously unstudied family of cyclic nucleotide phosphodiesterases, the PDE8s on adrenal, liver, and brown fat function. Preliminary evidence suggests that these PDEs are major regulators of cAMP controlled functions in these cell types. It is expected that the proposed studies will tell us which processes are regulated and how the regulation occurs at the molecular level. Just as another specific form of PDE is the target of the drug Viagra, so also it is quite possible that PDE8s may become the targets of drugs useful for treating adrenal, liver and adipose tissue dysfunction once we understand how they function in each of these tissues.