Kinetic and Structural Investigation of the Mechanism of Action of HLA-DO

Univ Of Massachusetts Med Sch Worcester, Worcester MA

Investigators

Linked publications & trials

Abstract

[unreadable] DESCRIPTION (provided by applicant): Kinetic and Structural Investigation of the Mechanism of Action of HLA-DO Antigen presentation is critical to immune system function and to the body's ability to defend against disease. To trigger an immune response, protein antigens are converted to short peptides and loaded onto major histocompatibility complex (MHC) class I or class II molecules for presentation at the surface of antigen-presenting cells. These peptide-MHC complexes can be recognized by antigen-specific receptors on T lymphocytes to elicit an immune response. This complex process is regulated by a variety of factors to allow recognition of pathogens while also preventing damage to healthy cells when fighting off disease. The loading of these peptides on to MHC class II molecules is catalyzed by the MHC class ll-like protein human leukocyte antigen (HLA)-DM. HLA-DM is critical for the generation of stable peptide-MHC complexes and alters the repertoire of peptides presented on the cell surface. HLA-DO is also a MHC class ll-like protein which associates with HLA-DM in certain cell types, like B lymphocytes. HLA-DO has been shown to inhibit HLA-DM function by an unknown mechanism. Through regulation of HLA-DM, HLA-DO modulates the repertoire of presented peptides. However, little is known about the interaction between these molecules and studies have been hindered by the limited availability of HLA-DO from native sources. This proposal is aimed at determining the mechanism of HLA-DO action on HLA-DM catalyzed peptide loading. To this end, soluble functionally active HLA-DO protein will be purified and a combination of biochemical and structural techniques will be employed. The step/s of HLA-DM catalyzed peptide exchange which are affected by HLA-DO will be studied using a fluorescence resonance energy transfer assay. X-ray crystallography of HLA-DO and the HLA-DO/HLA-DM complex will be used to elucidate the structural basis for inhibition. Both the pH dependence and the peptide dependence of HLA-DO inhibition will be investigated. Studying the HLA-DO mode of action is beneficial for understanding the pathogenesis of disease, such as autoimmune disease or how diseases like cancer evade the immune system, and the development of immunotheraputics to specifically target diseases. Antigen presentation is an important step in the body's immune response to protect against pathogens. This work studies the molecular mechanisms of this process. This understanding of how the body detects pathogens is important for fighting infection and can also be utilized in designing theraputics to target diseases. [unreadable] [unreadable] [unreadable]