Homozygous PiZZ alpha 1 proteinase inhibitor deficiency is associated with premature development of pulmonary emphysema and is the most common metabolic cause of liver disease in children. This deficiency probably results from an abnormally folded protein which is unable to efficiently traverse the secretory pathway and accumulates inside the cell. Thus, the net intracellular accumulation of alpha 1 PI in cells of deficient (PiZZ) individuals depends on a delicate balance between its synthesis, entry into and transport within the secretory pathway, and intracellular degradation. Recent studies in model experimental systems indicate that specific protein-protein interactions, involving proteins of the heat shock/stress family, are responsible for entry into the secretory pathway, for traversing the secretory pathway and for solubilization or degradation within this pathway. In work over the last 2 years, supported by this award, we have identified several different mechanisms for regulation of the synthesis of alpha 1 PI. In each case, when synthesis of alpha 1 PI increases, there is greater intracellular accumulation of the mutant protein in deficient cells. Preliminary experiments now indicate that the mutant alpha 1 PI protein binds inside the cell to a protein of the heat shock/stress family. Furthermore, there is a marked increase in synthesis of stress proteins in cells of deficient individuals. This increase in synthesis of stress proteins especially affects deficient individuals with liver disease as contrasted to those with lung disease or those without tissue injury. In this renewal application we will further define mechanisms by which synthesis of alpha 1 PI is regulated and initiate studies of the transport and degradation of alpha 1 PI. More specifically, we will characterize the novel mechanism by which elastase regulates the synthesis of its inhibitor, alpha 1 PI. Specific protein-protein interactions between mutant alpha 1 PI and proteins of the heat shock/stress family will be examined. Proteolytic systems responsible for intracellular degradation of alpha 1 PI will be identified in cell lines transfected with normal, mutant PiS and mutant PiZ alpha 1 PI alleles. finally, EBV-transformed B-Lymphocyte cell lines and skin fibroblasts from deficient individuals with each clinical phenotype will be transfected with the normal or mutant alpha 1 PI genes to determine whether there are differences in transport and degradation of mutant alpha 1 PI in deficient individuals with liver disease as contrasted with those having lung disease or those having no apparent tissue injury. These studies have broad application to the understanding of this common genetic deficiency, consequent injury to lung and liver and to the development of new therapeutic strategies.
Showing the most recent 10 out of 55 publications
