Discovery of Phosphorylated Peripherin as a Major Humoral Autoantigen in Type 1 Diabetes Mellitus

Abstract

Summary A major goal in understanding autoimmune diseases is to define the antigens that elicit a self-destructive immune response, but this is a difficult endeavor. In an effort to discover autoantigens associated with type 1 diabetes (T1D), we used epitope surrogate technology that screens combinatorial libraries of synthetic molecules for compounds that could recognize disease-linked autoantibodies and enrich them from serum. Autoantibodies from one patient revealed a highly phosphorylated form of peripherin, a neuroendocrine filament protein, as a candidate T1D antigen. Peripherin antibodies were detected in 67% of donor patient sera. Further analysis revealed that the T1D-associated antibodies only recognized a dimeric conformation of peripherin. These data explain why peripherin was dismissed as an important T1D antigen previously. The discovery of this novel autoantigen would not have been possible using standard methods, such as hybridizing serum antibodies to recombinant protein arrays, highlighting the power of epitope surrogate technology for probing the mechanism of autoimmune diseases.

Type III intermediate filaments as targets and effectors of electrophiles and oxidants

“…The role of this protein is unclear, but it seems to contribute to IF cytoskeleton organization and axonal elongation. The protein is a major autoantigen in type 1 diabetes [ 170 ] and appears in compact inclusions in several diseases, including amyotrophic lateral sclerosis (ALS). Screening for sequence variants in the peripherin gene ( PRPH ) has been performed in patients with ALS and several SNPs have been identified [ 171 ].…”

The Evolving Landscape of Autoantigen Discovery and Characterization in Type 1 Diabetes

“…Examples include islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) ( 9 , 10 ), chromogranin A (ChgA) ( 11 , 12 ), and islet amyloid polypeptide (IAPP) ( 13 – 15 ). Still others ( Table 3 ), e.g., peripherin ( 16 ), tetraspanin-7 ( 17 ), prolyl-4-hydroxylase β (P4Hb) ( 18 ), glucose-regulated protein 78 (GRP78) ( 19 ), urocortin-3 ( 20 ), and insulin gene enhancer protein isl-1 ( 20 ), have only more recently been discovered and warrant further exploration.…”

“…Finally, continued development of unbiased approaches for antigen and epitope identification is also urgently needed. In one such strategy, small molecules are used as “epitope surrogates” to enrich for T1D-specific autoantibodies from patient sera ( 16 ). The enriched antibodies are then used to identify the target protein(s), the approach that yielded the identification of phosphorylated peripherin as an autoantigen in T1D ( Table 3 ) ( 16 ).…”

“…In one such strategy, small molecules are used as “epitope surrogates” to enrich for T1D-specific autoantibodies from patient sera ( 16 ). The enriched antibodies are then used to identify the target protein(s), the approach that yielded the identification of phosphorylated peripherin as an autoantigen in T1D ( Table 3 ) ( 16 ). Likewise, serum screening of a nucleic acid–programmable, cell-free protein array, designed in an unbiased manner (i.e., without regard to pancreas expression level), recently revealed close to 20 previously unidentified targets of the autoantibody response in T1D ( 88 ).…”

High-throughput Identification of DNA-Encoded IgG Ligands that Distinguish Active and Latent Mycobacterium tuberculosis Infections

“…Epitope surrogates can serve as affinity reagents for selective purification of the disease-specific IgGs and subsequent native antigen identification. For example, an epitope surrogate discovered from a screen of T1D patient sera ultimately identified peripherin as a major T1D autoantigen 15 . The T1D-specific antibodies recognize only a highly phosphorylated, dimeric form of the protein, suggesting that native antigens of the disease-specific antibodies are unlikely to be “vanilla” peptides or recombinantly-expressed proteins.…”