Molecular pathogenesis of alpha-1-antitrypsin deficiency

Alpha-1 antitrypsin (α1-AT) is the most abundant circulating protease inhibitor. The common severe Z allele of α1-AT (Glu342Lys) causes the protein to form ordered polymers that are retained within the endoplasmic reticulum of hepatocytes. These polymers form the periodic acid-Schiff positive inclusions that are associated with cirrhosis. The lack of circulating α1-AT predisposes the Z α1-AT homozygote to early onset emphysema. We review here the molecular basis of α1-AT deficiency and show how understanding the liver disease provides new insights in the pathobiology of the associated emphysema. The mechanism of α1-AT deficiency provides a paradigm for a wider group of conditions that we have termed the serpinopathies. We also examine the strategies that are being pursued to develop novel therapies for α1-AT deficiency. This review considers our understanding of the pathobiology of α1-AT deficiency and then illustrate the therapeutic possibilities that can ensue once we understand basic mechanisms of disease.