目的:B细胞活化因子(BAFF)与其受体(BAFFR)的结合在成熟的B细胞中激活了许多必需的促存活功能。BAFFR基因中的空突变导致完全BAFFR缺乏,并在从未成熟B细胞到成熟B细胞的过渡中导致B细胞发育受阻,从而导致B淋巴细胞减少和低丙种球蛋白血症。除了完全的BAFFR缺乏,在患有共同可变免疫缺陷(CVID)的患者中发现了编码BAFFR错义突变的单核苷酸变体,自身免疫,或者B细胞淋巴瘤.由于尚不清楚这些变体在多大程度上干扰BAFFR的活性,我们进行了遗传关联研究,并开发了一种细胞系统,可以对有关寡聚化的BAFFR变体进行无偏分析,信令,和胞外域脱落。
方法:除了遗传关联研究,BAFFR变体P21R,A52T,G64V,DUP92-95,P146S,和H159Y通过慢病毒基因转移在DG-75Burkitt淋巴瘤细胞中表达,并分析其对BAFFR功能的影响。
结果:BAFF与BAFFR的结合受P21R和A52T的影响。P21R干扰了BAFFR的自发低聚,A52T,G64V,P146SP21R和P146S降低了BAFF依赖性NF-κB2的激活,而BAFFR与B细胞抗原受体组分CD79B和AKT磷酸化之间的相互作用被P21R削弱,A52T,G64V,还有DUP92-95.P21R,G64V,和DUP92-95干扰ERK1/2的磷酸化,而BAFF诱导的BAFFR胞外域脱落仅被P21R损害。
结论:尽管所有变体都改变了BAFFR功能,并有可能作为修饰因子促进初级抗体缺乏的发展,自身免疫,和淋巴瘤,P21R是发现与CVID正相关的唯一变体。
Binding of the B cell activating factor (BAFF) to its receptor (BAFFR) activates in mature B cells many essential pro-survival functions. Null mutations in the BAFFR gene result in complete BAFFR deficiency and cause a block in B cell development at the transition from immature to mature B cells leading therefore to B lymphopenia and hypogammaglobulinemia. In addition to complete BAFFR deficiency, single nucleotide variants encoding BAFFR missense mutations were found in patients suffering from common variable immunodeficiency (CVID), autoimmunity, or B cell lymphomas. As it remained unclear to which extent such variants disturb the activity of BAFFR, we performed genetic association studies and developed a cellular system that allows the unbiased analysis of BAFFR variants regarding oligomerization, signaling, and ectodomain shedding.
In addition to genetic association studies, the BAFFR variants P21R, A52T, G64V, DUP92-95, P146S, and H159Y were expressed by lentiviral gene transfer in DG-75 Burkitt\'s lymphoma cells and analyzed for their impacts on BAFFR function.
Binding of BAFF to BAFFR was affected by P21R and A52T. Spontaneous oligomerization of BAFFR was disturbed by P21R, A52T, G64V, and P146S. BAFF-dependent activation of NF-κB2 was reduced by P21R and P146S, while interactions between BAFFR and the B cell antigen receptor component CD79B and AKT phosphorylation were impaired by P21R, A52T, G64V, and DUP92-95. P21R, G64V, and DUP92-95 interfered with phosphorylation of ERK1/2, while BAFF-induced shedding of the BAFFR ectodomain was only impaired by P21R.
Although all variants change BAFFR function and have the potential to contribute as modifiers to the development of primary antibody deficiencies, autoimmunity, and lymphoma, P21R is the only variant that was found to correlate positively with CVID.