Cell Biology of ASIC2 in Glioma

描述(申请人提供)：胶质瘤是一种由分化的胶质细胞通过鲜为人知的恶性转化过程而产生的原发脑瘤。脑肿瘤表现出复杂的生物学特性，因为它们具有显著的抗原性异质性、基因组中的可变突变以及侵袭正常脑组织的倾向。在研究从被诊断为不同程度恶性肿瘤的患者获得的胶质瘤中，我们观察到电压非依赖性、阿米洛利可抑制的内向Na+电导的表达，这在正常人类神经胶质细胞或低级别肿瘤中不存在。我们推测，高级别胶质瘤细胞表现出这一特征的Na+电导的功能性上调。如果这一传导途径被阿米洛利或从蜘蛛毒液中分离的多肽阻断，胶质瘤细胞的迁移、细胞增殖和细胞体积调节都受到影响。因此，支持这种传导的通道膜蛋白是潜在的独特的治疗靶点。本申请中提出的研究有一个目标，即彻底表征这种对阿米洛利敏感的Na+电导途径的一个亚基(ASIC2)通过细胞生物合成途径进行交通的能力。此外，我们假设这个亚基(ASIC2)是转录调控的。因此，在恶性脑肿瘤中，ASIC2要么不表达，要么保留在细胞内。有两个特定的目的：1)检验ASIC2在高级别肿瘤细胞亚群中缺乏质膜表达是由于通道错误折叠导致内质网滞留的假说；2)检验在大多数高级别胶质瘤中ASIC2基因表达受脑肿瘤微环境特异性因素转录调控的假说。我们预计，这项工作将为调节脑瘤中对阿米洛利敏感的Na+通道的分子机制提供新的基础性见解。此外，这项工作将为这些通道在胶质瘤细胞的发病机制和生命周期中的作用提供重要线索。

DESCRIPTION (provided by applicant): Gliomas are primary brain tumors that arise from differentiated glial cells through a poorly understood process of malignant transformation. Brain tumors display a complex biology because of their remarkable degree of antigenic heterogeneity, variable mutations in their genome, and their propensity for invasion into normal brain tissue. In studying gliomas obtained from patients that were diagnosed with tumors of varying degrees of malignancy, we observed the expression of a voltage-independent, amiloride-inhibitable, inward Na+ conductance that was not present in normal human glial cells or in low-grade tumors. We hypothesize that high-grade glioma cells show functional up-regulation of this characteristic Na + conductance. Glioma cell migration, cell proliferation, and cell volume regulation are all compromised if this conductance pathway is blocked with amiloride or by a peptide isolated from a spider venom. Thus, the channel membrane proteins that underlie this conductance are potentially unique, therapeutic targets. The research proposed in this application has one objective of characterizing thoroughly the ability of one subunit (ASIC2) of this amiloride-sensitive Na+ conductance pathway to traffic through the cellular biosynthetic pathway. In addition, we hypothesize that this same subunit (ASIC2) is transcriptionally regulated. Thus, in malignant brain tumors, ASIC2 either is not expressed or is retained intracellularly. There are two Specific Aims: 1) to test the hypothesis that lack of plasma membrane expression of ASIC2 in a subset of high-grade tumor cells is a consequence of endoplasmic reticulum retention due to channel misfolding; and 2) to test the hypothesis that in the majority of high-grade gliomas ASIC2 gene expression is transcriptionally regulated by factors specific to the brain tumor microenvironment. We anticipate that this work will provide new fundamental insights into the molecular mechanisms involved in the regulation of amiloride-sensitive Na + channels in brain tumors. Moreover, this work will provide important clues as to the role of these channels in the pathogenesis and life cycle of glioma cells.