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（申请者提供）：盘状盘齿骨柱前孢子和前柄细胞之间的通讯协调着盘状盘齿柱的终末分化。信号包括一个34个氨基酸的肽，SDF-2，其序列与神经肽DBI（安定结合抑制剂）相关。神经递质GABA也通过类似于哺乳动物GABAB受体的g蛋白偶联受体在盘基骨鞘中作为信号。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时间的进化中被保存下来，而受体在某些情况下发生了变化。我们将进一步阐明细胞间信号传导的详细机制，因为这些结果似乎与哺乳动物中枢神经系统的信号传导有关，并可能揭示神经精神疾病的潜在机制。当预孢子和预柄细胞分别准备包封和空泡化时，它们之间存在复杂的信息交换。SDF-2是由孢子前细胞释放的一种叫做AcbA的蛋白质水解过程产生的。在低水平的SDF-2或GABA启动后，加工发生在前秆细胞表面。孢子前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AcbA在核内体中的积累和随后的释放至关重要。我们将确定低水平SDF-2或GABA的胞吐反应是否依赖于cAMP依赖性蛋白激酶PKA的信号传导。胞外AcbA被膜包埋的预茎特异性蛋白酶TagC进行蛋白水解裂解，TagC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活性。我们的研究结果表明，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，这种配体结合在广泛使用的药物安定（安定）的目标上。我们观察到GABA似乎能诱导快速胞吐，这不仅说明了它在盘基骨鞘中的启动活性，而且为更好地理解胞吐控制的基本过程提供了一个测试系统。这些研究将共同为改善神经系统疾病的诊断和治疗奠定基础。