The goodpasture autoantigen -: Identification of multiple cryptic epitopes on the NC1 domain of the α3(IV) collagen chain
The goodpasture autoantigen -: Identification of multiple cryptic epitopes on the NC1 domain of the α3(IV) collagen chain
复制标题
DOI：
10.1074/jbc.275.8.6030
复制
发表时间：
2000-02-25
影响因子：
4.8
通讯作者：
Hudson, BG
中科院分区：
文献类型：
--
作者：
Borza, DB;Netzer, KO;Hudson, BG
Goodpasture （GP）病是一种自身免疫性疾病，其中针对TV型胶原蛋白α 3（TV）链的自身抗体与肾小球和肺泡基底膜结合，导致进行性肾小球肾炎和肺出血。在α 3（IV）链的IV型胶原蛋白的非胶原结构域（NC1结构域）上发现了两个主要的构象表位区域，即残基17-31 （E-A）和127-141 (E-B) （Netzer, k - o）。等（1999）[j]。为了确定这些区域是两个不同的表位还是形成一个单一的表位，我们在含有E-A和/或E-B区域的固定化NC1嵌合体上用亲和层析法分离了三个GP血清。因此，对α 3(IV)NC1结构域具有不同表位特异性的四个GP抗体亚群进行了分离和表征。它们分别被命名为GP(A)， GP(B)， GP（AB）和GP(X)，以反映它们分别与E-A， E-B，两个区域和不反应。因此，区域E-A和E-B分别包含构成GP(A)、GP(B)和GP（AB）抗体三个不同表位的关键氨基酸，而GP抗体的表位位于不同的未知区域。GP(A)抗体始终具有免疫优势，占α 3(IV)NC1总免疫反应性的60-65%；因此，它们可能在发病机制中起主要作用。E-A和E-B区域靠得很近，因为它们共同形成了Mab3的表位，Mab3是一种与GP自身抗体结合的单克隆抗体。所有GP表位都被隔离在组织中发现的NC1结构域的六聚体构型中，除非六聚体发生解离，否则抗体无法结合，这提示了GP疾病的可能病因机制。GP抗体能够从天然人肾小球基底膜六聚体中提取α 3(IV)NC1单体，但不能提取二聚体，这一特性可能对该病的发病机制具有重要意义。
Goodpasture (GP) disease is an autoimmune disorder in which autoantibodies against the alpha 3(TV) chain of type TV collagen bind to the glomerular and alveolar basement membranes, causing progressive glomerulonephritis and pulmonary hemorrhage, Two major conformational epitope regions have been identified on the noncollagenous domain of type IV collagen (NC1 domain) of the alpha 3(IV) chain as residues 17-31 (E-A) and 127-141 (E-B) (Netzer, K.-O. et al. (1999) J. Biol. Chem. 274, 11267-11274), To determine whether these regions are two distinct epitopes or form a single epitope, three GP sera were fractionated by affinity chromatography on immobilized NC1 chimeras containing the E-A and/or the E-B region. Four subpopulations of GP antibodies with distinct epitope specificity for the alpha 3(IV)NC1 domain were thus separated and characterized. They were designated GP(A), GP(B), GP(AB) and GP(X), to reflect their reactivity with E-A only, E-B only, both regions, and neither, respectively. Hence, regions E-A and E-B encompass critical amino acids that constitute three distinct epitopes for GP(A), GP(B), and GP(AB) antibodies, respectively, whereas the epitope for GP, antibodies is located in a different unknown region. The GP(A) antibodies were consistently immunodominant, accounting for 60-65% of the total immunoreactivity to alpha 3(IV)NC1; thus, they probably play a major role in pathogenesis. Regions E-A and E-B are held in close proximity because they jointly form the epitope for Mab3, a monoclonal antibody that competes for binding with GP autoantibodies. All GP epitopes are sequestered in the hexamer configuration of the NC1 domain found in tissues and are inaccessible for antibody binding unless dissociation of the hexamer occurs, suggesting a possible mechanism for etiology of GP disease. GP antibodies have the capacity to extract alpha 3(IV)NC1 monomers, but not dimers, from native human glomerular basement membrane hexamers, a property that may be of fundamental importance for the pathogenesis of the disease.