Human α1-Antitrypsin Binds to Heat-Shock Protein gp96 and Protects from Endogenous gp96-Mediated Injury In vivo
Open Access
- 1 January 2013
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Immunology
- Vol. 4, 61674
- https://doi.org/10.3389/fimmu.2013.00320
Abstract
The extracellular form of the abundant heat-shock protein, gp96, is involved in human autoimmune pathologies. In patients with type 1 diabetes, circulating gp96 is found to be elevated, and is bound to the acute-phase protein, α1-antitrypsin (AAT). The two molecules also engage intracellularly during the physiological folding of AAT. AAT therapy promotes pancreatic islet survival in both transplantation and autoimmune diabetes models, and several clinical trials are currently examining AAT therapy for individuals with type 1 diabetes. However, its mechanism of action is yet unknown. Here, we examine whether the protective activity of AAT is related to binding of extracellular gp96. Primary mouse islets, macrophages, and dendritic cells were added recombinant gp96 in the presence of clinical-grade human AAT (hAAT, Glassia™, Kamada Ltd., Israel). Islet function was evaluated by insulin release. The effect of hAAT on IL-1β/IFNγ-induced gp96 cell-surface levels was also evaluated. In vivo, skin transplantation was performed for examination of robust immune responses, and systemic inflammation was induced by cecal puncture. Endogenous gp96 was inhibited by gp96-inhibitory peptide (gp96i, Compugen Ltd., Israel) in an allogeneic islet transplantation model. Our findings indicate that hAAT binds to gp96 and diminishes gp96-induced inflammatory responses; e.g., hAAT-treated gp96-stimulated islets released less pro-inflammatory cytokines (IL-1β by 6.16-fold and TNFα by 2.69-fold) and regained gp96-disrupted insulin release. hAAT reduced cell activation during both skin transplantation and systemic inflammation, as well as lowered inducible surface levels of gp96 on immune cells. Finally, inhibition of gp96 significantly improved immediate islet graft function. These results suggest that hAAT is a regulator of gp96-mediated inflammatory responses, an increasingly appreciated endogenous damage response with relevance to human pathologies that are exacerbated by tissue injury.This publication has 41 references indexed in Scilit:
- Tacrolimus Inhibits the Revascularization of Isolated Pancreatic IsletsPLOS ONE, 2013
- The danger theory: 20 years laterFrontiers in Immunology, 2012
- Strategies toward single-donor islets of Langerhans transplantationCurrent Opinion in Organ Transplantation, 2011
- Trying to Reset the Clock on Type 1 DiabetesScience, 2011
- Decoding Cell Death Signals in Inflammation and ImmunityCell, 2010
- Immunological aspects of pancreatic islet cell transplantationExpert Review of Clinical Immunology, 2010
- Transgenic Expression of Hsc70 in Pancreatic Islets Enhances Autoimmune Diabetes in Response to β Cell DamageThe Journal of Immunology, 2009
- Heat Shock Protein 96 Is Elevated in Rheumatoid Arthritis and Activates Macrophages Primarily via TLR2 SignalingThe Journal of Immunology, 2009
- Rapamycin Induces Autophagy in Islets: Relevance in Islet TransplantationTransplantation Proceedings, 2009
- Roles of Heat Shock Protein gp96 in the ER Quality Control: Redundant or Unique Function?Molecules and Cells, 2005