Cross-Presentation of Glycoprotein 96–Associated Antigens on Major Histocompatibility Complex Class I Molecules Requires Receptor-Mediated Endocytosis

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.

Induction of cell stress through gene transfer of an engineered heat shock transcription factor enhances tumor immunogenicity

“…Additionally, the expressed heat shock proteins function both as additional adjuvant 14,15 and efficiently chaperone tumor antigens to antigen-presenting cells. [16][17][18] The relative importance of these distinct facets of heat shock protein activity may relate to the receptor molecules utilized by released heat shock proteins. Thus, heat shock proteins binding to CD14 14 or Toll-like receptors 15 may function to enhance innate immunity via antigenpresenting cell activation.…”

The heat shock protein Hsp70 enhances antigen-specific proliferation of human CD4+ memory T cells

“…Members of the HSP70 family possess a peptide binding domain and are able to bind and release the hydrophobic domains of polypeptides in an ATP-dependent manner. Upon cell stress and cell death, HSP:peptide complexes are released [2] and subsequently taken up by professional APC in a receptor-mediated process [3][4][5][6][7], enabling them to cross-present CTL and Th cell epitopes [8,9]. On the other hand HSP induce the maturation and activation of APC, such as dendritic cells, similarly to other inflammatory mediators [6,10].…”

“…Mammalian HSP such as the human cytosolic 70-kDa HSP (Hsp70) or gp96 are able to form highly immunogenic HSP:peptide complexes and to elicit antigen-specific CD8 + T cell responses to the chaperoned peptides [8,9]. In contrast, the role for HSP:peptide complexes in the MHC class II pathway is less clear, although several findings indicate that HSP:peptide complexes also facilitate the presentation of MHC class II-restricted epitopes.…”

The pathophysiology of photosensitivity in lupus erythematosus

“…The specificity of immune responses to HSPs derives from the peptides to which they are bound (159,160). Recent data has shed light on the mechanisms involved in the elicitation of specific CTL responses by HSPs: peptides complexed to gp96, hsp90 and hsp70 released from cells are taken up by receptor-mediated endocytosis on APCs including DCs and macrophages and re-presented to T cells in the context of MHC class I (161)(162)(163)(164)(165)(166). Interestingly, CD91, now identified as the receptor for peptide loaded-gp96 on macrophages, is also present on keratinocytes (162).…”