Epithelial Expression of an Interstitial Lung Disease-Associated Mutation in Surfactant Protein-C Modulates Recruitment and Activation of Key Myeloid Cell Populations in Mice.
Mutations in the gene encoding surfactant protein C (SFTPC) have led to a broad range of phenotypes from neonatal respiratory distress syndrome to adult interstitial lung disease.
A novel surfactant protein C mutation resulting in aberrant protein processing and altered subcellular localization causes infantile interstitial lung disease.
While a lack of dimeric SP-B was found only in the sole subject with hereditary SP-B deficiency, low or absent SP-C was observed not only in surfactant dysfunction disorders but also in patients with other diffuse parenchymal lung diseases pathogenetically related to the alveolar surfactant region.
We detected a novel c.163C>T mutation located in the mature domain of SFTPC associated with ILD that altered the subcellular localization of proSP-C in A549 cells.
Furthermore, to understand how the pro-SP-C BRICHOS domain present in the ER lumen can interact with the TM segment of pro-SP-C, we studied the membrane insertion properties of the recombinant form of the pro-SP-C BRICHOS domain and two ILD-associated mutants.
Mutation of threonine for isoleucine at codon 73 (I73T) in the human surfactant protein C (hSP-C) gene (SFTPC) accounts for a significant portion of SFTPC mutations associated with interstitial lung disease (ILD).
ProSP-C contains a BRICHOS domain, in which many ILD-associated mutations are localized, and the BRICHOS domain can prevent SP-C from forming amyloid-like fibrils.
To identify possible starting points for therapeutic intervention, we stably transfected A549 alveolar epithelial cells with several proSP-C mutations previously found in patients suffering from ILD.
A 333-base deletion involving part of exon 4 and the adjacent intron of the gene encoding surfactant protein C was identified in a child with interstitial lung disease.
Conclusion Since ABCA3 mutations seem to be a heterogeneous entity with various phenotypes, we recommend genetic testing for mutations in SP-C and ABCA3 genes to be considered in children with unexplained interstitial lung disease.
More important, it offers the updated viewpoint that mutations in the BRICHOS domain of surfactant protein C, which cause interstitial lung disease and induce cell death specifically in lung epithelial cells, in effect provide genetic proof that the Witschi Hypothesis is indeed the correct theory to explain the pathogenesis of fibrosis in the lungs.
Our findings shed new light on the pathomechanisms underlying SP-C deficiency associated ILD and provide insight into the mechanisms by which drugs currently used in ILD therapy act.
The BRICHOS domain was initially defined from sequence alignments of the Bri protein associated with familial dementia, chondromodulin associated with chondrosarcoma and surfactant protein C precursor (proSP-C) associated with respiratory distress syndrome and interstitial lung disease (ILD).
These findings demonstrate that subclinical fibrotic changes may be present in family members of patients with SFTPC mutation-associated interstitial lung disease and suggest that ABCA3 variants could affect disease pathogenesis.
We identified two novel mutations in highly conserved areas of the SFTPC gene, and show that heterozygotes for the mutations have normal lung function and are unaffected by COPD and interstitial lung disease.
To present diagnosis and treatment modalities of children with interstitial lung disease associated with frequent or rare surfactant protein C gene (SFTPC) mutation.
The most frequent SFTPC mutation in ILD patients leads to a threonine for isoleucine substitution at position 73 (I73T) of the SP-C preprotein (proSP-C), however little is known about the cellular consequences of SP-CI73T expression.