Unraveling the structural basis for the unusually rich association of human leukocyte antigen DQ2.5 with class-II-associated invariant chain peptides

作者：Thanh Binh Nguyen; Jayaraman Priya; Bergseng Elin; Madhusudhan M S; Kim Chu Young^*; Sollid Ludvig M^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2017, 292(22): 9218-9228.

DOI：10.1074/jbc.M117.785139

Human leukocyte antigen (HLA)-DQ2.5 (DQA1* 05/ DQB1* 02) is a class-II major histocompatibility complex protein associated with both type 1 diabetes and celiac disease. One unusual feature of DQ2.5 is its high class-II-associated invariant chain peptide (CLIP) content. Moreover, HLA-DQ2.5 preferentially binds the non-canonical CLIP2 over the canonical CLIP1. To better understand the structural basis of HLA-DQ2.5 ' s unusual CLIP association characteristics, better insight into the HLADQ2.5.CLIP complex structures is required. To this end, we determined the X-ray crystal structure of the HLA-DQ2.5.CLIP1 and HLA-DQ2.5.CLIP2 complexes at 2.73 and 2.20 angstrom, respectively. We found that HLA-DQ2.5 has an unusually large P4 pocket and a positively charged peptide-binding groove that together promote preferential binding of CLIP2 over CLIP1. An alpha 9-alpha 22-alpha 24-alpha 31-beta 86-beta 90 hydrogen bond network located at the bottom of the peptide-binding groove, spanning from the P1 to P4 pockets, renders the residues in this region relatively immobile. This hydrogen bond network, along with a deletion mutation at alpha 53, may lead to HLA-DM insensitivity in HLA-DQ2.5. A molecular dynamics simulation experiment reported here and recent biochemical studies by others support this hypothesis. The diminished HLA-DM sensitivity is the likely reason for the CLIP-rich phenotype of HLA-DQ2.5.

• 出版日期2017-6-2