A large and complex surface area of the lung is exposed to the airborne environment, putting it at risk for protein function injury by invading organisms, environmental stressors and inherited disease, such as loss of alpha-1- antitrypsin (AAT) protection in AAT deficiency (AATD) driven by 68 clinically validated variants. Protein homeostasis or proteostasis is a multi-layered protein folding program (the proteostasis network (PN)) that is initiated during differentiation and development to protect the folding biology of each specialized cell type, and is essential for the protection and renewal of complex tissue/organ environments during aging in response to the environment and inherited/somatic acquired disease. This proposal directly addresses an urgent and unmet need to understand the role of liver-derived plasma AAT in variant driven AATD liver and lung (chronic obstructive pulmonary disease (COPD)/emphysema (EPS)) disorders where in the latter AAT is now recognized as the major genetic modifier of disease progression. In order to address the linked problem in liver and lung pathophysiologies leading to AATD/COPD/EPS in response to the inherited AAT variant population found in the population, we have developed a number of approaches that monitor synthesis, folding, trafficking, secretion, monomer/polymer ratio (monomer/polymer index (MPIdx)) and neutrophil elastase (NE) inhibitory activity of WT and AAT variants from liver and lung cell lines, and primary hepatocyte/iPS cell culture models. Importantly, we have developed robust high throughput screening (HTS) (96/384-well format) methodologies to quantitatively assess in parallel the impact of a broad range of biologics (si/shRNA reagents and/or overexpression vectors) and chemical (small molecules found in high diversity chemical libraries) that not only promote correction of AAT variant secretion, but enhance the NE inhibitory activity of variants and improve its MPIdx in the cell and secreted pools. We hypothesize that biologics and small chemical molecules that specifically affect the proteostasis pathways directing the secretion of functional Z-AAT and/or augmenting the secretion of wild-type (WT) AAT will be instrumental in maintaining a healthy lung to provide a natural corrective/protective environment to prevent or halt the progression of liver and airway disease. To pursue this hypothesis, in Aim 1 we will characterize chaperone specific heat shock (HS) protein 70-90 (HS70-90) arm of the PN;
Aim 2 will focus on those belonging to the redox arm of the PN. Both arms of the PN will be examined in multiple cell-based (heterologous and primary) assays and a simple murine model of disease where we will follow AAT variant levels in plasma in response to biologic and/or chemical correctors. Our combined Aims focus on understanding the largely uncharacterized links between coupled liver and lung (patho)physiologies associated with inherited AAT variant imposed functional deficiency in plasma to identify known/unknown biological pathways relevant to both AATD liver disease and COPD/EPS that may have high therapeutic clinical relevance.
A large and complex surface area of the lung is exposed to the airborne environment, putting it at risk for protein function injury by environmental stressors and inherited disease such as loss of AAT protection in AATD (driven by ~68 clinically validated variants) leading to COPD/EPS. Protein homeostasis or proteostasis is a multi-layered protein folding program that is initiated during differentiation and development to protect the folding biology of each specialized cell type, and is essential for the protection and renewal of complex tissue/organ environments during aging in response to the environment and inherited disease. To develop new approaches for liver and lung AATD disease, the proposed studies will characterize the impact of the chaperone arm (Aim 1) and the oxidative stress arm (Aim 2) of proteostasis to understand the largely uncharacterized links between liver and lung (patho)physiologies in response to the collective of inherited AAT variant imposed functional deficiency in serum/plasma to identify known and unknown biological pathways that may have high therapeutic clinical relevance for mitigation of disease