Chemical approaches for studying the biology of CD38

描述(由申请人提供)：科学界充分认识到了解生物标志物以充分利用它们在疾病诊断和治疗以及生物医学研究中的重要性。CD38最初被认为是造血细胞的分化标志，在许多其他类型的细胞中都存在，它的去调控被发现与几种不同的人类疾病有关，包括白血病、社会行为缺陷、糖尿病和骨质疏松症。了解CD38在各种正常和病理条件下的作用，有可能为这些疾病的治疗提供新的方法。到目前为止，由于该领域研究人员的努力，人们已经获得了一些关于CD38的知识，尽管有限。CD38既是一种酶，也是一种受体。酶活性可将烟酰胺腺嘌呤二核苷酸(NAD)转化为二磷酸腺苷核糖(ADPR)和环状ADPR(CADPR)，将NAD磷酸(NADP)转化为烟酸腺嘌呤二核苷酸(NAADP)。CADPR和NAADP都是强大的钙信使，可以触发内库的钙释放。作为一种受体，当CD38被某些配体激活时，可以触发细胞内蛋白的磷酸化，包括c-Cb1和丝裂原激活的蛋白激酶(MAPK)。然而，尽管已经积累了上述知识，但CD38在大多数正常和病理情况下所起的确切作用目前还知之甚少。几个悬而未决的问题阻碍了人们对CD38功能的清晰和完整的了解。例如，CD38如何获得其NAD或NADP底物，CD38是否存在于细胞内细胞器中，以及受体功能如何影响酶功能。在这个计划中，我们将开发和使用化学工具，特别是可以在活细胞中共价标记CD38的NAD类似物，来解决这些关于CD38生物学的重要问题。这些CD38探针具有独特的特性，如细胞通透性，与CD38的配基结合的兼容性，以及抑制CD38酶活性的能力。这些小分子探针可用于实时跟踪CD38在活细胞中的转运，确定CD38在细胞内的分布，并分离和鉴定未知的CD38配体。使用其他方法很难实现这些实验。我们的研究将导致CD38生物化学的更详细的机制图，这将有助于了解CD38在各种正常和病理条件下的功能，并可能导致治疗涉及CD38的疾病的新方法，如白血病、糖尿病、自闭症和骨质疏松症。此外，CD38的NAD代谢能力可以对其他依赖NAD的酶，特别是依赖NAD的脱乙酰酶(Sirtuins)和聚(ADP-核糖)聚合酶(PARP)产生重大影响。了解CD38是如何工作的，应该有助于了解CD38和其他NAD依赖的酶之间的潜在相互作用。 公共卫生相关性：CD38对免疫细胞分化和功能、胰岛素分泌和神经肽释放很重要。它已被发现与几种人类疾病有关，如白血病和糖尿病。我们提出的研究将有助于了解CD38在正常和病理条件下所起的作用，并可能导致治疗涉及CD38的人类疾病的新方法。

DESCRIPTION (provided by applicant): The significance of understanding biomarkers to take full advantage of them in disease diagnosis and treatment as well as in biomedical research is well recognized by the science community. CD38, originally identified as a differentiation marker for hematopoietic cells, is present in many other types of cells, and its deregulation is found to contribute to several different human diseases, including leukemia, social behavior defects, diabetes, and osteoporosis. Understanding the roles CD38 plays in various normal and pathological conditions has the potential to offer new ways to treat these diseases. So far, some knowledge about CD38 has been acquired, though limited, thanks to the efforts from researchers in the field. CD38 acts both as an enzyme and a receptor. The enzymatic activity can convert nicotinamide adenine dinucleotide (NAD) to adenosine diphosphate ribose (ADPR) and cyclic ADPR (cADPR), and NAD phosphate (NADP) to nicotinic acid adenine dinucleotide phosphate (NAADP). Both cADPR and NAADP are potent Ca2+ messengers that can trigger Ca2+ release from internal stores. As a receptor, when activated by certain ligands, CD38 can trigger the phosphorylation of intracellular proteins, including c-Cbl and mitogen-activated protein kinases (MAPK). However, the exact roles CD38 plays in most normal and pathological conditions are poorly understood at present, despite the accumulation of the knowledge mentioned above. Several unanswered questions prevent a clear and complete understanding of CD38 function. For example, how CD38 gains access to its NAD or NADP substrate, whether CD38 is present in intracellular organelles, and how the receptor function affects the enzymatic function. In this proposal, we will develop and use chemical tools, particularly NAD analogs that can covalently label CD38 in live cells, to address these important questions concerning CD38 biology. These CD38 probes have unique features, such as cell permeability, compatibility with ligand binding to CD38, and the ability to inhibit CD38 enzymatic activity. These small molecule probes can be used to track CD38 trafficking in real time in live cells, determine the intracellular distribution of CD38, and isolate and identify unknown CD38 ligands. These experiments cannot be easily achieved using other methods. Our studies will lead to a more detailed mechanistic picture of CD38 biochemistry, which will help to understand the function of CD38 in various normal and pathological conditions and potentially lead to new ways to treat diseases involving CD38, such as leukemia, diabetes, autism, and osteoporosis. In addition, the NAD metabolizing capability of CD38 can have a significant impact on other NAD-dependent enzymes, particularly the NAD-dependent deacetylases (sirtuins) and poly(ADP-ribose) polymerases (PARPs). Understanding how CD38 works should shed lights on the potential interactions between CD38 and other NAD-dependent enzymes. PUBLIC HEALTH RELEVANCE: CD38 is important for immune cell differentiation and function, insulin secretion, and neuropeptide release. It has been found to be involved in several human diseases, such as leukemia and diabetes. Our proposed study will help to understand the roles of CD38 plays in normal and pathological conditions, and potentially lead to new ways to treat human diseases involving CD38.