Effects of glucose-regulated protein94 (Grp94) on Ig secretion from human blood mononuclear cells

Abstract

Grp94 is the main endoplasmic reticulum-resident heat shock protein (HSP) that besides chaperoning native proteins, displays important modulatory effects on both the innate and adaptive immune response. Since the knowledge of a direct influence of Grp94 on the humoral response is lacking, in this work we tested the effect of Grp94 on Ig secretion from peripheral blood mononuclear cells (PBMCs) of five normal volunteers. The concentration of Ig secreted in the medium after incubation of 15 days was found increased in a dose-dependent manner in the presence of Grp94, used at the final concentrations of 10 and 100 ng/ml. However, by measuring the Ig secretion at different incubation times, it was apparent that maximal percent stimulation by Grp94 occurred at 7 days, decreasing thereafter. In addition, the pattern of Ig secretion in time significantly differed in the presence of Grp94 with respect to that of control PBMCs. Grp94 also stimulated in a dose-dependent manner the PBMC proliferation, an effect that preceded the Ig secretion and was accompanied by morphological changes of cells similar to those induced by the pokeweed mitogen. Effects of Grp94 on PBMCs were mediated by an intense activation of the MEK-ERK1/2 pathway and by an increased expression of HSP90. Results indicate that Grp94 can activate the humoral response by a cytokine-like, cell-mediated mechanism that leads to an accelerated process of B cell maturation and differentiation.

Identification and characterization of novel ER-based hsp90 gene in the red flour beetle, Tribolium castaneum

“…The upregulation of ER-based Hsp90 is used as a hallmark of responses to ER stress (Eletto et al 2010). Recent studies have demonstrated ER-based HSP90 is involved in maturation of proteins destined for cell surface display or export and plays a vital role in both the adaptive and innate immune systems (Marzec et al 2012;Tramentozzi et al 2011;Yang et al 2007). Moreover, it is also required during the early developmental stage in C. elegans, fly, and mouse (Marzec et al 2012;Maynard et al 2010;Wanderling et al 2007).…”

Cell Surface GRP94 as a Novel Emerging Therapeutic Target for Monoclonal Antibody Cancer Therapy

“…Zheng et al demonstrated that GRP94 is important for stimulating dendritic cell maturation and inducing efficient T-cell priming [ 86 ]. Furthermore, Suto et al showed direct evidence that assembled complexes of GRP94 and synthetic peptides can be presented again by an antigen-presenting cell (APC) to promote T-cell activation [ 87 ]. Biswas et al also identified that the N-terminal fragment (amino acids 1–355) of GRP94 is responsible for peptide presentation to T-cells [ 56 ].…”

Grp94 in complexes with IgG is a soluble diagnostic marker of gastrointestinal tumors and displays immune-stimulating activity on peripheral blood immune cells

“…Although we cannot exclude that Grp94-IgG complexes might have a direct effect on B cells, other observations would rather favor the alternative possibility of an indirect, mostly TNFα-mediated mechanism. First, in a previous work we reported that Grp94, added to PBMCs in the same experimental conditions as the present ones, could significantly reduce the IgG secretion in human PBMCs only when Grp94 was the antigen expressed by immune cells, and this effect did not involve B lymphocytes directly [ 53 ]. Second, TNFα produced by macrophages is known to suppress the development of human B cells into Ig-producing cells with the consequent inhibition of Ig secretion [ 54 ].…”

“…The blood sample was collected in EDTAcontaining Vacutainer tubes (Greiner Bio-one Company, Kremsmünster, Austria) the day before the surgery and immediately centrifuged at 1300 × g for 10 min to separate plasma from other cellular components. Plasma was frozen and stored at −80°C for further analysis, while PBMCs were purified as described [ 53 ].…”