Dataset Information

Molecular Mechanism of Z ?1-Antitrypsin Deficiency.

ABSTRACT: The Z mutation (E342K) of ?1-antitrypsin (?1-AT), carried by 4% of Northern Europeans, predisposes to early onset of emphysema due to decreased functional ?1-AT in the lung and to liver cirrhosis due to accumulation of polymers in hepatocytes. However, it remains unclear why the Z mutation causes intracellular polymerization of nascent Z ?1-AT and why 15% of the expressed Z ?1-AT is secreted into circulation as functional, but polymerogenic, monomers. Here, we solve the crystal structure of the Z-monomer and have engineered replacements to assess the conformational role of residue Glu-342 in ?1-AT. The results reveal that Z ?1-AT has a labile strand 5 of the central ?-sheet A (s5A) with a consequent equilibrium between a native inhibitory conformation, as in its crystal structure here, and an aberrant conformation with s5A only partially incorporated into the central ?-sheet. This aberrant conformation, induced by the loss of interactions from the Glu-342 side chain, explains why Z ?1-AT is prone to polymerization and readily binds to a 6-mer peptide, and it supports that annealing of s5A into the central ?-sheet is a crucial step in the serpins' metastable conformational formation. The demonstration that the aberrant conformation can be rectified through stabilization of the labile s5A by binding of a small molecule opens a potential therapeutic approach for Z ?1-AT deficiency.

SUBMITTER: Huang X

PROVIDER: S-EPMC4957051 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Molecular Mechanism of Z α1-Antitrypsin Deficiency.

Huang Xin X Zheng Ying Y Zhang Fei F Wei Zhenquan Z Wang Yugang Y Carrell Robin W RW Read Randy J RJ Chen Guo-Qiang GQ Zhou Aiwu A

The Journal of biological chemistry 20160531 30

The Z mutation (E342K) of α1-antitrypsin (α1-AT), carried by 4% of Northern Europeans, predisposes to early onset of emphysema due to decreased functional α1-AT in the lung and to liver cirrhosis due to accumulation of polymers in hepatocytes. However, it remains unclear why the Z mutation causes intracellular polymerization of nascent Z α1-AT and why 15% of the expressed Z α1-AT is secreted into circulation as functional, but polymerogenic, monomers. Here, we solve the crystal structure of the ...[more]

PMID: 27246852

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Project description:α1-anti-trypsin (A1AT), encoded by SERPINA1, is a neutrophil elastase inhibitor that controls the inflammatory response in the lung. Severe A1AT deficiency increases risk for Chronic Obstructive Pulmonary Disease (COPD), however, the role of A1AT in COPD in non-deficient individuals is not well known. We identify a 2.1-fold increase (p = 2.5x10-6) in the use of a distal poly-adenylation site in primary lung tissue RNA-seq in 82 COPD cases when compared to 64 controls and replicate this in an independent study of 376 COPD and 267 controls. This alternative polyadenylation event involves two sites, a proximal and distal site, 61 and 1683 nucleotides downstream of the A1AT stop codon. To characterize this event, we measured the distal ratio in human primary tissue short read RNA-seq data and corroborated our results with long read RNA-seq data. Integrating these results with 3' end RNA-seq and nanoluciferase reporter assay experiments we show that use of the distal site yields mRNA transcripts with over 50-fold decreased translation efficiency and A1AT expression. We identified seven RNA binding proteins using enhanced CrossLinking and ImmunoPrecipitation precipitation (eCLIP) with one or more binding sites in the SERPINA1 3' UTR. We combined these data with measurements of the distal ratio in shRNA knockdown experiments, nuclear and cytoplasmic fractionation, and chemical RNA structure probing. We identify Quaking Homolog (QKI) as a modulator of SERPINA1 mRNA translation and confirm the role of QKI in SERPINA1 translation with luciferase reporter assays. Analysis of single-cell RNA-seq showed differences in the distribution of the SERPINA1 distal ratio among hepatocytes, macrophages, αβ-Tcells and plasma cells in the liver. Alveolar Type 1,2, dendritic cells and macrophages also vary in their distal ratio in the lung. Our work reveals a complex post-transcriptional mechanism that regulates alternative polyadenylation and A1AT expression in COPD.

Dataset Information

Molecular Mechanism of Z ?1-Antitrypsin Deficiency.

Publications

Molecular Mechanism of Z α1-Antitrypsin Deficiency.

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