Mapping the Role of Unfolded Protein Response Genes in Hepatocytes Expressing Z Alpha-1-Antitrypsin

Funded by a Grant from the Alpha-1 Foundation


Individuals with PI*ZZ alpha-1-antitrypsin (AAT) deficiency have an increased risk of developing liver disease. The risk factors associated with the development of clinically apparent liver disease are unclear but likely include both environmental and other genetic factors. Recently, we have evaluated and compared global liver gene expression with 43,000 gene Stanford spotted micorarrays using liver tissue from PI*MM and PI*ZZ individuals. Approximately 1000 genes have significantly different expression in normal versus deficient individuals. These genes tend to cluster into functional groups that include protein degradation, glycosylation, protein folding, intracellular protein transport, signal transduction and apoptosis. In addition, using quantitative PCR, selected genes involved in the unfolded protein response (UPR), cytokines and elements of the innate immune response are significantly increased in PI*ZZ liver tissue. Together, these gene expression differences between liver tissue from normal and deficient individuals indicate that there are major intracellular alterations in response to misfolded AAT that may have biological consequences beyond the primary cell expressing Z AAT. We hypothesize that the protein products of these genes may play a role in liver injury and amplification/initiation of inflammation. To determine which of these genes’ expression are altered in response to misfolded Z AAT in the hepatocyte we have established a liver cell line from an individual with PI*ZZ AAT deficiency. Using this liver cell line, expression of the UPR-related genes will be determined. Following up-regulation Z AAT expression in the Z hepatocyte cell UPR-related gene expression will be determined and compared before and after stimulation using quantitative PCR. To determine if production of Z AAT is responsible for the change in gene expression, siRNA targeted to the Z AAT mRNA will be used to knock down AAT protein production. Finally, to evaluate the effect of UPR-related gene expression the TNFa stimulated liver cell line will treated with increasing doses of 4-PBA and the specific inhibitor of Z AAT polymerization inhibitor peptide, FLEAIG. The results of these studies may provide candidate genes to examine in deficient subjects with and with out liver disease and provide potential new therapeutic targets leading to the uncoupling of the UPR and end organ damage.