Fabian Heinz, Huser Hans, Loll Bernhard, Ziegler Andreas, Naumann Dieter, Uchanska-Ziegler Barbara
Robert Koch Institute, 13353Berlin, Germany.
Arthritis Rheum. 2010 Apr;62(4):978-87. doi: 10.1002/art.27316.
Although the products of the HLA subtypes B2705 and B2709 differ only in residue 116 (Asp versus His) within their peptide-binding grooves, they are differentially associated with inflammatory rheumatic diseases such as ankylosing spondylitis (AS): B2705 occurs in AS patients, whereas B2709 is only rarely encountered. The reasons for this distinct association are still unclear but could include subtype-specific conformational and dynamic properties of these antigens. The present study was undertaken to investigate structural and dynamic differences between B2705 and B2709 and their possible relationship to subtype-specific disease association.
The membrane-distal segments of the B2705 and B2709 heavy chains were expressed in vitro and reconstituted together with beta(2)-microglobulin and a peptide. HLA-B27 complexes loaded with 2 self peptides (TIS [RRLPIFSRL] and pVIPR [RRKWRRWHL]) and a sequence-related viral peptide (pLMP2 [RRRWRRLTV]) were studied by isotope-edited infrared spectroscopy to detect differences in their structure and flexibility at physiologic temperature.
Our analyses revealed the existence of subtype-specific conformational differences between the 2 HLA-B27 heavy chains at physiologic temperature, which are undetectable using x-ray crystallography. Irrespective of the bound peptide, the heavy chain of the B2705 complex exhibited higher conformational flexibility than the B2709 heavy chain.
The present study demonstrates the existence of previously undetected systematic conformational and dynamic differences between the heavy chains of the 2 HLA-B27 subtypes. Since effector cell recognition of cells expressing HLA antigens is dependent on the dynamic properties of the interacting cell surface molecules, this HLA-B27 subtype-specific heavy chain flexibility could have a role in the distinct association of HLA-B27 subtypes with spondylarthritides.
尽管HLA亚型B2705和B2709的产物在其肽结合槽内仅在第116位残基（天冬氨酸与组氨酸）上存在差异，但它们与炎性风湿性疾病如强直性脊柱炎（AS）的关联有所不同：B2705见于AS患者，而B2709则很少见。这种明显关联的原因尚不清楚，但可能包括这些抗原的亚型特异性构象和动力学特性。本研究旨在探究B2705和B2709之间的结构和动力学差异及其与亚型特异性疾病关联的可能关系。
B2705和B2709重链的膜远端片段在体外表达，并与β2-微球蛋白和一种肽一起重构。通过同位素编辑红外光谱研究加载有2种自身肽（TIS [RRLPIFSRL]和pVIPR [RRKWRRWHL]）以及一种序列相关病毒肽（pLMP2 [RRRWRRLTV]）的HLA-B27复合物，以检测其在生理温度下的结构和柔韧性差异。
我们的分析揭示了在生理温度下两种HLA-B27重链之间存在亚型特异性构象差异，而使用X射线晶体学无法检测到这些差异。无论结合的肽如何，B2705复合物的重链比B2709重链表现出更高的构象柔韧性。
本研究证明了两种HLA-B27亚型的重链之间存在先前未检测到的系统性构象和动力学差异。由于效应细胞对表达HLA抗原的细胞的识别取决于相互作用的细胞表面分子的动力学特性，这种HLA-B27亚型特异性重链柔韧性可能在HLA-B27亚型与脊柱关节炎的明显关联中起作用。
