Intercellular signaling during terminal differentiation

终末分化过程中的细胞间信号传导

• 批准号: 7130324
• 负责人: WILLIAM F LOOMIS
• 金额: $ 26.23万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-26 至 2010-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7130324
• 关键词: Dictyostelium; acyl coA; binding sites; cell cell interaction; cell cycle; cell differentiation; cell surface receptors; endopeptidases; exocytosis; gamma aminobutyrate; inhibitor /antagonist; ligands; neuropeptides; other phosphotransferase; protein kinase A; protein sequence; proteolysis; protozoal genetics; receptor binding; site directed mutagenesis

DESCRIPTION (provided by applicant): Communication between prespore and prestalk cells coordinates terminal differentiation in Dictyostelium discoideum. The signals include a 34 amino acid peptide, SDF-2, that has a sequence related to that of the neuropeptide DBI (Diazepam Binding Inhibitor). The neurotransmitter GABA is also used as a signal in Dictyostelium by acting through a G-protein coupled receptor similar to the GABAB receptor of mammals. The SDF-2 receptor, DhkA, on the other hand, is a "two-component" histidine kinase completely unrelated to the DBI receptors, GABAA and "peripheral type" BZ receptors. It seems that intercellular signals have been conserved over long periods of evolution while the receptors have changed in some cases. We will further elucidate the detailed mechanisms of intercellular signaling in this genetically tractable system since the results appear to have bearing on signaling in the mammalian central nervous system and may shed light on mechanisms underlying neuropsychiatric disorders. There is a complicated interchange of information between prespore and prestalk cells as they prepare to encapsulate and vacuolize, respectively. SDF-2 is generated by proteolytic processing of a protein, AcbA, released from prespore cells. Processing occurs on the surface of prestalk cells after priming by low levels of SDF-2 or by GABA. Prespore cells respond to priming by rapid release of AcbA from vesicles. AcbA is an acyl-CoA binding protein as is the precursor of DBI. Using site-directed mutagenesis we will determine whether this activity is essential for accumulation of AcbA in endosomes and subsequent release. We will determine whether exocytosis in response to either low levels of SDF-2 or GABA is dependent on signaling through the cAMP dependent protein kinase PKA. Extracellular AcbA is proteolytically cleaved by the membrane embedded prestalk specific protease TagC, which is only exposed following priming by either low levels of SDF-2 or GABA. We will determine whether this process is also dependent on PKA activity. Our results suggest that the precursor of the mammalian neuropeptide DBI, ACBP, may be synthesized in one cell type, stored in vesicles, and processed to the active peptides by another cell type. Such interactions could modulate the levels of this natural ligand that binds at the target of the widely used drug diazepam (Valium). Our observations that GABA appears to induces rapid exocytosis not only accounts for its priming activity in Dictyostelium but provides a test system for better understanding of the basic processes controlling exocytosis. Together these studies will add to the foundation for improvements in the diagnosis and treatment of neurological diseases.

描述（由申请人提供）：前孢子和前柄细胞之间的通讯协调盘基网柄菌的终末分化。这些信号包括 34 个氨基酸的肽 SDF-2，其序列与神经肽 DBI（地西泮结合抑制剂）相关。神经递质 GABA 也通过类似于哺乳动物 GABAB 受体的 G 蛋白偶联受体发挥作用，在盘基网柄菌中用作信号。另一方面，SDF-2 受体 DhkA 是一种“双组分”组氨酸激酶，与 DBI 受体、GABAA 和“外周型”BZ 受体完全无关。细胞间信号似乎在长期的进化过程中得到了保留，而受体在某些情况下发生了变化。我们将进一步阐明这种遗传易处理系统中细胞间信号传导的详细机制，因为结果似乎与哺乳动物中枢神经系统中的信号传导有关，并可能揭示神经精神疾病的潜在机制。当前孢子和前茎细胞分别准备封装和形成空泡时，它们之间存在复杂的信息交换。 SDF-2 是通过前孢子细胞释放的蛋白质 AcbA 的蛋白水解加工产生的。在低水平的 SDF-2 或 GABA 引发后，前茎细胞表面会发生加工。前孢子细胞通过从囊泡中快速释放 AcbA 来响应启动。 AcbA 是一种酰基辅酶 A 结合蛋白，是 DBI 的前体。使用定点诱变，我们将确定这种活性是否对于 AcbA 在内体中的积累和随后的释放至关重要。我们将确定响应低水平的 SDF-2 或 GABA 的胞吐作用是否依赖于 cAMP 依赖性蛋白激酶 PKA 的信号传导。胞外 AcbA 被膜嵌入的前柄特异性蛋白酶 TagC 蛋白水解裂解，该蛋白酶仅在低水平的 SDF-2 或 GABA 引发后暴露。我们将确定该过程是否也依赖于 PKA 活动。我们的结果表明，哺乳动物神经肽 DBI 的前体 ACBP 可能在一种细胞类型中合成，储存在囊泡中，并由另一种细胞类型加工成活性肽。这种相互作用可以调节这种天然配体的水平，该配体与广泛使用的药物地西泮（安定）的靶标结合。我们观察到 GABA 似乎诱导快速胞吐作用，这不仅解释了其在盘基网柄菌中的启动活性，而且提供了一个测试系统，以更好地了解控制胞吐作用的基本过程。这些研究将为改善神经系统疾病的诊断和治疗奠定基础。