title: 6-mer peptide selectively anneals to a pathogenic serpin conformation and blocks polymerization. Implications for the prevention of Z alpha(1)-antitrypsin-related cirrhosis.
abstract: Conformational diseases such as amyloidosis, Alzheimer's disease, prion diseases, and the serpinopathies are all caused by structural rearrangements within a protein that transform it into a pathological species. These diseases are typified by the Z variant of alpha(1)-antitrypsin (E342K), which causes the retention of protein within hepatocytes as inclusion bodies that are associated with neonatal hepatitis and cirrhosis. The inclusion bodies result from the Z mutation perturbing the conformation of the protein, which facilitates a sequential interaction between the reactive center loop of one molecule and beta-sheet A of a second. Therapies to prevent liver disease must block this reactive loop-beta-sheet polymerization without interfering with other proteins of similar tertiary structure. We have used reactive loop peptides to explore the differences between the pathogenic Z and normal M alpha(1)-antitrypsin. The results show that the reactive loop is likely to be partially inserted into beta-sheet A in Z alpha(1)-antitrypsin. This conformational difference from M alpha(1)-antitrypsin was exploited with a 6-mer reactive loop peptide (FLEAIG) that selectively and stably bound Z alpha(1)-antitrypsin. The importance of this finding is that the peptide prevented the polymerization of Z alpha(1)-antitrypsin and did not significantly anneal to other proteins (such as antithrombin, alpha(1)-antichymotrypsin, and plasminogen activator inhibitor-1) with a similar tertiary structure. These findings provide a lead compound for the development of small molecule inhibitors that can be used to treat patients with Z alpha(1)-antitrypsin deficiency. Furthermore they demonstrate how a conformational disease process can be selectively inhibited with a small peptide.
authors.affiliation: Respiratory Medicine Unit, Department of Medicine, University of Cambridge, Cambridge CB2 2XY, United Kingdom. rm232@cam.ac.uk
authors.forename: Ravi
authors.initials: R
authors.lastname: Mahadeva
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Dafforn
authors.forename: Robin W
authors.initials: RW
authors.lastname: Carrell
authors.forename: David A
authors.initials: DA
authors.lastname: Lomas
mesh_terms: D020106:Acrylamide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015843:Serpins / Q000737:chemistry*; D013997:Time Factors; D014508:Urea / Q000494:pharmacology; D000515:alpha 1-Antitrypsin / Q000737:chemistry*; D019896:alpha 1-Antitrypsin Deficiency / Q000097:blood*
chemical_list: D010455:Peptides; D015843:Serpins; D000515:alpha 1-Antitrypsin; D020106:Acrylamide; D014508:Urea