Xia Jiang, Siegel Matthew, Bergseng Elin, Sollid Ludvig M, Khosla Chaitan
Departments of Chemistry, Chemical Engineering, and Biochemistry, Stanford University, Stanford, CA 94305-5025, USA.
J Am Chem Soc. 2006 Feb 15;128(6):1859-67. doi: 10.1021/ja056423o.
Human leukocyte antigen DQ2 is a class II major histocompatibility complex protein that plays a critical role in the pathogenesis of Celiac Sprue by binding to epitopes derived from dietary gluten and triggering the inflammatory response of disease-specific T cells. Inhibition of DQ2-mediated antigen presentation in the small intestinal mucosa of Celiac Sprue patients therefore represents a potentially attractive mode of therapy for this widespread but unmet medical need. Starting from a pro-inflammatory, proteolytically resistant, 33-residue peptide, LQLQPFPQPELPYPQPELPYPQPELPYPQPQPF, we embarked upon a systematic effort to dissect the relationships between peptide structure and DQ2 affinity and to translate these insights into prototypical DQ2 blocking agents. Three structural determinants within the first 20 residues of this 33-mer peptide, including a PQPELPYPQ epitope, its N-terminal flanking sequence, and a downstream Glu residue, were found to be important for DQ2 binding. Guided by the X-ray crystal structure of DQ2, the L11 and L18 residues in the truncated 20-mer analogue were replaced with sterically bulky groups so as to retain high DQ2 affinity but abrogate T cell recognition. A dimeric ligand, synthesized by regiospecific coupling of the 20-mer peptide with a bifunctional linker, was identified as an especially potent DQ2 binding agent. Two such ligands were able to attenuate the proliferation of disease-specific T cell lines in response to gluten antigens and, therefore, represent prototypical examples of pharmacologically suitable DQ2 blocking agents for the potential treatment of Celiac Sprue.
人类白细胞抗原DQ2是一种II类主要组织相容性复合体蛋白，它通过与源自膳食麸质的表位结合并触发疾病特异性T细胞的炎症反应，在乳糜泻的发病机制中起关键作用。因此，抑制乳糜泻患者小肠黏膜中DQ2介导的抗原呈递，代表了针对这种广泛存在但未满足的医疗需求的一种潜在有吸引力的治疗方式。从一种促炎性、蛋白水解抗性的33个残基的肽LQLQPFPQPELPYPQPELPYPQPELPYPQPQPF开始，我们展开了一项系统性工作，以剖析肽结构与DQ2亲和力之间的关系，并将这些见解转化为典型的DQ2阻断剂。在这个33肽的前20个残基中有三个结构决定因素，包括一个PQPELPYPQ表位、其N端侧翼序列和一个下游的Glu残基，被发现对DQ2结合很重要。以DQ2的X射线晶体结构为指导，将截短的20肽类似物中的L11和L18残基替换为空间位阻较大的基团，以保持高DQ2亲和力但消除T细胞识别。通过将20肽与双功能连接子进行区域特异性偶联合成的二聚体配体，被鉴定为一种特别有效的DQ2结合剂。两种这样的配体能够减弱疾病特异性T细胞系对麸质抗原的增殖反应，因此代表了潜在治疗乳糜泻的药理学上合适的DQ2阻断剂的典型例子。
