Chemokine Signaling Defects in Human Immunodeficiency

奇思妙想综合征是一种常染色体显性遗传病，导致先天性低丙种球蛋白血症。 中性粒细胞减少，可变T细胞缺乏，以及对人类乳头瘤病毒感染的异常易感性。 对这种疾病患者的分子遗传学研究已经将该特征基因定位在2q21号染色体上，并发现编码趋化因子受体CXCR4的基因发生了截断突变。通过突变受体的信号在患者来源的淋巴母细胞中得到增强，这与激活机制一致。受体及其配体在HIV细胞进入感染过程中的作用，以及在B细胞发育和淋巴组织组织中的作用而被广泛研究。缺乏CXCR4受体会影响早期B细胞的存活，但携带截短的CXCR4受体的患者的淋巴细胞缺陷不仅仅是数量上的，这增加了无法迁移到适当的发育间隔和/或成熟缺陷的可能性。这项建议将侧重于在表达突变CXCR4受体的人和转基因小鼠细胞中，在趋化、信号转导和β-arrestin介导的受体内化水平上建立截断突变的影响。CXCL12激活CXCR4后的细胞内信号转导是复杂的，涉及多个效应器。初步证据表明，G蛋白偶联和ERK1/2信号的调节在突发综合征疾病细胞中受到损害。生化分析涉及CXCR4信号和趋化作用的信号通路将在不同成熟阶段的B细胞中进行。体外研究将与体内CXCR4突变对淋巴器官发育的影响相结合。除了提供对疾病病理生理学的洞察外， 由此产生的数据将提供关于受体尾部结构域在 受体反应性的发育调节。拟议的研究与计划项目申请的项目2共享，重点是免疫缺陷疾病中低丙种球蛋白血症的机制，以及迁移缺陷在疾病病理生理学中的可能作用。

WHIM syndrome is an autosomal dominant disease causing hypogammaglobulinernia, congenital neutropenia, variable T cell deficiency, and an unusual predisposition to human papillomavirus infection. Molecular genetic studies in patients with the disease have localized the trait locus to chromosome 2q21 and revealed truncating mutations in the gene encoding the chemokine receptor CXCR4. Signaling through the mutant receptors was enhanced in patient-derived lymphoblastoid cells, consistent with an activating mechanism. The receptor and its ligand are well studied because of their roles in HIV cell entry during infection and in B cell development and lymphoid tissue organization. Absence of the receptor compromises early B cell survival, but lymphocyte defects in patients carrying truncated CXCR4 receptors are not simply quantitative, raising the possibility of failure to migrate to the appropriate developmental compartment and/or maturation defects. This proposal will focus on establishing the effect of truncation mutations at the level of chemotaxis, signal transduction, and beta-arrestin-mediated receptor internalization in human and genetically modified murine cells expressing mutant CXCR4 receptors. Intracellular signaling following CXCR4 activation by CXCL12 is complex, involving multiple effectors. Preliminary evidence suggests that regulation of G-protein-coupled and ERK1/2 signaling is impaired in WHIM syndrome disease cells. Biochemical analysis of signaling pathways implicated in CXCR4 signaling and chemotaxis will be performed in B cells at distinct stages of maturation. In vitro studies will be coupled to determination of the in vivo effect of CXCR4 mutations on lymphoid organ development. In addition to providing insight into the disease pathophysiology, the resulting data will provide additional information on the role of the receptor tail domain in the developmental regulation of receptor responsiveness. The proposed studies share with Project 2 of the Program Project application a focus on mechanisms of hypogammaglobulinemia in immunodeficiency diseases and the possible role of migration defects in disease pathophysiology.