Cell Biology of ASIC2 in Glioma

描述（由申请人提供）：胶质瘤是一种原发性脑肿瘤，由分化的胶质细胞通过一个知之甚少的恶性转化过程产生。脑肿瘤由于其显著程度的抗原异质性、其基因组中的可变突变以及其侵入正常脑组织的倾向而显示出复杂的生物学。在研究从诊断为不同程度恶性肿瘤的患者中获得的神经胶质瘤时，我们观察到电压非依赖性、阿米洛利可耐受的内向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，高级别胶质瘤细胞显示功能上调这一特点Na +电导。如果用阿米洛利或从蜘蛛毒液中分离的肽阻断这种传导途径，胶质瘤细胞迁移、细胞增殖和细胞体积调节都会受到损害。因此，作为这种传导基础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的一个目的是彻底表征这种阿米洛利敏感性Na+传导途径的一个亚基（ASIC 2）通过细胞生物合成途径进行运输的能力。此外，我们假设，这个相同的亚基（ASIC 2）是转录调节。因此，在恶性脑肿瘤中，ASIC 2要么不表达，要么保留在细胞内。有两个具体目标：1）检验在高级别肿瘤细胞亚群中缺乏ASIC 2质膜表达是由于通道错误折叠导致内质网滞留的结果的假设;和2）检验在大多数高级别胶质瘤中ASIC 2基因表达由脑肿瘤微环境特异性因子转录调控的假设。我们预计，这项工作将提供新的基本见解的分子机制参与调节阿米洛利敏感的Na +通道在脑肿瘤。此外，这项工作将提供重要的线索，这些通道的发病机制和胶质瘤细胞的生命周期中的作用。

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.