Surfactant protein A2 mutations associated with pulmonary fibrosis lead to protein instability and endoplasmic reticulum stress

Meenakshi Maitra, Yongyu Wang, Robert D. Gerard, Carole R. Mendelson, Christine Kim Garcia

Research output: Contribution to journalArticle

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Abstract

Rare heterozygous mutations in the gene encoding surfactant protein A2 (SP-A2, SFTPA2) are associated with adult-onset pulmonary fibrosis and adenocarcinoma of the lung. We have previously shown that two recombinant SP-A2 mutant proteins (G231V and F198S) remain within the endoplasmic reticulum (ER) of A549 cells and are not secreted into the culture medium. The pathogenic mechanism of the mutant proteins is unknown. Here we analyze all common and rare variants of the surfactant protein A2, SP-A2, in both A549 cells and in primary type II alveolar epithelial cells. We show that, in contrast with all other SP-A2 variants, the mutant proteins are not secreted into the medium with wild-type SP-A isoforms, form fewer intracellular dimer and trimer oligomers, are partially insoluble in 0.5% Nonidet P-40 lysates of transfected A549 cells, and demonstrate greater protein instability in chymotrypsin proteolytic digestions. Both the G231V and F198S mutant SP-A2 proteins are destroyed via the ER-association degradation pathway. Expression of the mutant proteins increases the transcription of a BiP-reporter construct, expression of BiP protein, and production of an ER stress-induced XBP-1 spliced product. Human bronchoalveolar wash samples from individuals who are heterozygous for the G231V mutation have similar levels of total SP-A as normal family members, which suggests that the mechanism of disease does not involve an overt lack of secreted SP-A but instead involves an increase in ER stress of resident type II alveolar epithelial cells.

Original languageEnglish (US)
Pages (from-to)22103-22113
Number of pages11
JournalJournal of Biological Chemistry
Volume285
Issue number29
DOIs
StatePublished - Jul 16 2010

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Endoplasmic Reticulum Stress
Pulmonary Fibrosis
varespladib methyl
Surface-Active Agents
Mutant Proteins
Mutation
Proteins
Alveolar Epithelial Cells
Endoplasmic Reticulum
Gene encoding
Chymotrypsin
Transcription
Oligomers
Dimers
Culture Media
Protein Isoforms
Association reactions
Degradation
Digestion
Genes

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Surfactant protein A2 mutations associated with pulmonary fibrosis lead to protein instability and endoplasmic reticulum stress. / Maitra, Meenakshi; Wang, Yongyu; Gerard, Robert D.; Mendelson, Carole R.; Garcia, Christine Kim.

In: Journal of Biological Chemistry, Vol. 285, No. 29, 16.07.2010, p. 22103-22113.

Research output: Contribution to journalArticle

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