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Cross-presentation of glycoprotein 96-associated antigens on major histocompatibility complex class I molecules
H Singh-Jasuja1, R E Toes, P Spee
1Institute for Cell Biology, Department of Immunology, University of Tübingen, Germany.
Insights
Heat shock proteins like glycoprotein 96 (gp96) require specific receptor uptake by antigen-presenting cells (APCs) to activate cytotoxic T lymphocytes (CTLs). This receptor-mediated process is crucial for gp96-chaperoned peptide cross-presentation and subsequent CTL responses.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Heat shock proteins (HSPs), including glycoprotein 96 (gp96), are known to elicit cytotoxic T lymphocyte (CTL) responses.
- The precise mechanisms by which gp96 facilitates antigen presentation and CTL activation remain under investigation.
Purpose of the Study:
- To elucidate the role of receptor-mediated uptake in gp96-chaperoned peptide presentation.
- To identify the cell types capable of binding and internalizing gp96.
- To understand how gp96 facilitates cross-presentation of cellular antigens.
Main Methods:
- Investigated gp96 binding and uptake by antigen-presenting cells (APCs) in human and mouse models.
- Utilized receptor-mediated endocytosis assays and co-localization studies with MHC molecules.
- Assessed CTL activation using gp96 isolated from cells expressing specific epitopes and inhibitory controls.
Main Results:
- Specific receptor-mediated uptake of gp96 by professional APCs (dendritic cells, macrophages, B cells) is essential for CTL activation.
- gp96 is rapidly internalized by APCs and co-localizes with MHC class I and II molecules.
- gp96-associated peptides are presented in an MHC class I-restricted manner, leading to specific CTL activation.
Conclusions:
- Receptor-mediated endocytosis of gp96 by APCs is critical for the cross-presentation of cellular antigens.
- This process enables the induction of specific CTL responses against cellular targets.
- The findings clarify the molecular mechanisms underlying gp96-mediated immune surveillance and anti-tumor immunity.
Abstract:
Heat shock proteins (HSPs) like glycoprotein (gp)96 (glucose-regulated protein 94 [grp94]) are able to induce specific cytotoxic T lymphocyte (CTL) responses against cells from which they originate. Here, we demonstrate that for CTL activation by gp96-chaperoned peptides, specific receptor-mediated uptake of gp96 by antigen-presenting cells (APCs) is required. Moreover, we show that in both humans and mice, only professional APCs like dendritic cells (DCs), macrophages, and B cells, but not T cells, are able to bind gp96. The binding is saturable and can be inhibited using unlabeled gp96 molecules. Receptor binding by APCs leads to a rapid internalization of gp96, which colocalizes with endocytosed major histocompatibility complex (MHC) class I and class II molecules in endosomal compartments. Incubation of gp96 molecules isolated from cells expressing an adenovirus type 5 E1B epitope with the DC line D1 results in the activation of E1B-specific CTLs. This CTL activation can be specifically inhibited by the addition of irrelevant gp96 molecules not associated with E1B peptides. Our results demonstrate that only receptor-mediated endocytosis of gp96 molecules leads to MHC class I-restricted re-presentation of gp96-associated peptides and CTL activation; non-receptor-mediated, nonspecific endocytosis is not able to do so. Thus, we provide evidence on the mechanisms by which gp96 is participating in the cross-presentation of antigens from cellular origin.