Promiscuous binding of invariant chain-derived CLIP peptide to distinct HLA-I molecules revealed in leukemic cells

• Published in: PloS one 2012-04, Vol.7 (4), p.e34649-e34649
• Main Authors: van Luijn, Marvin M, van de Loosdrecht, Arjan A, Lampen, Margit H, van Veelen, Peter A, Zevenbergen, Adri, Kester, Michel G D, de Ru, Arnoud H, Ossenkoppele, Gert J, van Hall, Thorbald, van Ham, S Marieke
• Format: Article
• Language: English
• Subjects: Aberration; Algorithms; Alleles; Amino Acid Sequence; Animals; Antigen presentation; Antigen Presentation - immunology; Antigens, Differentiation, B-Lymphocyte - chemistry; Antigens, Differentiation, B-Lymphocyte - metabolism; B cells; B7 antigen; Binding; Biology; Blood transfusions; Cancer; Cell Line, Tumor; Cell Membrane - metabolism; Cell surface; Chains; Class II-associated invariant chain peptides; Cytotoxicity; Genetic engineering; Grooves; Hematology; Histocompatibility antigen HLA; Histocompatibility Antigens Class I - genetics; Histocompatibility Antigens Class I - metabolism; Histocompatibility Antigens Class II - chemistry; Histocompatibility Antigens Class II - metabolism; HLA antigens; HLA-A2 Antigen - genetics; HLA-A2 Antigen - metabolism; HLA-B7 Antigen - genetics; HLA-B7 Antigen - metabolism; Humans; Immunization; Immunology; Invariant chain; Invariants; Laboratories; Leukemia; Leukemia - pathology; Lymphocytes; Lymphocytes T; Medicine; Mice; Mice, Transgenic; Peptides; Protein Binding; Proteins; T cells; Transgenic mice
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0034649

Antigen presentation by HLA class I (HLA-I) and HLA class II (HLA-II) complexes is achieved by proteins that are specific for their respective processing pathway. The invariant chain (Ii)-derived peptide CLIP is required for HLA-II-mediated antigen presentation by stabilizing HLA-II molecules before antigen loading through transient and promiscuous binding to different HLA-II peptide grooves. Here, we demonstrate alternative binding of CLIP to surface HLA-I molecules on leukemic cells. In HLA-II-negative AML cells, we found plasma membrane display of the CLIP peptide. Silencing Ii in AML cells resulted in reduced HLA-I cell surface display, which indicated a direct role of CLIP in the HLA-I antigen presentation pathway. In HLA-I-specific peptide eluates from B-LCLs, five Ii-derived peptides were identified, of which two were from the CLIP region. In vitro peptide binding assays strikingly revealed that the eluted CLIP peptide RMATPLLMQALPM efficiently bound to four distinct HLA-I supertypes (-A2, -B7, -A3, -B40). Furthermore, shorter length variants of this CLIP peptide also bound to these four supertypes, although in silico algorithms only predicted binding to HLA-A2 or -B7. Immunization of HLA-A2 transgenic mice with these peptides did not induce CTL responses. Together these data show a remarkable promiscuity of CLIP for binding to a wide variety of HLA-I molecules. The found participation of CLIP in the HLA-I antigen presentation pathway could reflect an aberrant mechanism in leukemic cells, but might also lead to elucidation of novel processing pathways or immune escape mechanisms.