Regulation of redox homeostasis and integrated stress response by Protein Disulfide Isomerase (PDI): mechanisms and role in the pathophysiology and therapy of vascular diseases

Abstract

Redox homeostasis depends on the regulated production of reactive oxygen species (ROS) via enzymatic sources such as the Nox family NADPH oxidase complex, the main source of ROs in vascular cells. Recent studies from our laboratory disclosed an important role of PDI in the regulation of NADPH oxidase. The important functional effects of PDI in NADPH oxidase in a number of distinct cell types, the physical proximity between POI and NADPH oxidase complex subunits and the important functional versatility of PDI regarding its interaction with other proteins, chaperone effect, redox control of membrane proteins and protein traffic strongly indicate that the study of mechanisms whereby PDI affects NADPH oxidase is likely to provide important information with respect to the regulation of cellular redox homeostasis by NADPH oxidase. The main objective of this Theme Project is to investigate such mechanisms in depth. In parallel, considering that PDI is an endoplasmic reticulum (ER) enzyme, we worked over our last Theme Project on the hypothesis that PDI has a role in the convergence between oxidative stress and ER stress and we collected data suggestive of such an important stress convergence in cellular models. It is possible that the effects of PDI on cellular redox homeostasis in vascular diseases strongly merge with the occurrence of ER stress. Therefore, a second goal of our Project is to further our understanding of redox PDI effects in the context of the convergence between NADPH oxidase and integrative cell response to ER stress. Specific goals of our project are: 1) to develop peptide and molecular tools to promote loss- or gain-of-function of PDI; 2) to investigate some post-translational modifications of PDI; 3) to evaluate the role of PDI in cell migration and associated redox and non-redox mechanisms; 4) to study the effect of PDI in the regulation of NO-superoxide interaction during laminar shear stress; 5) to investigate the role of lipd droplets as integrative platforms of redox processes dependent on PDI and NADPH oxidase; 6) to investigate mechanisms whereby redox processes, NADPH oxidase and PDI affect the adaptation to sustained ER stress in cell models; 7) to investigate, during vascular repair following angioplasty-induced injury, the effects of PDI modulation in redox homeostasis and ER stress signaling, as well as neointima extension and endothelial thrombogenicity; 8) to investigate a possible effect of PDI, redox processes and ER stress in the vascular phenotype associated with Marfan' s Syndrome. These results may indicate entirely novel pathways that can lead to therapeutic interventions for the control of redox homeostasis in vascular diseases. (AU)