Crystal structure of the major diabetes autoantigen insulinoma-associated protein 2 reveals distinctive immune epitopes

Insulinoma-associated protein-2 (IA-2) is a major autoantigen in type I diabetes that occurs through autoimmune-mediated P-cell destruction. We present here the crystal structure of the protein tyrosine phosphatase (PTP)-like domain of human IA-2. The structure reveals a canonical PTP domain with the closed WPD loop over the active site pocket, explaining the lack of enzyme activity in the native protein. The structural interpretation of previous mutagenesis studies indicates that the B-cell epitopes are concentrated on two distinctive regions on peripheral loops of the central P-sheet surrounding T-cell epitopes within the sheet. The detailed structural information on immune epitopes provides a framework for the future development of immune intervention strategies against diabetes.