A nonaggregating surfactant protein C mutant is misdirected to early endosomes and disrupts phospholipid recycling.

Interstitial lung disease in both children and adults has been linked to mutations in the lung-specific surfactant protein C (SFTPC) gene. Among these, the missense mutation [isoleucine to threonine at codon 73 = human surfactant protein C (hSP-C(I73T) )] accounts for ∼30% of all described SFTPC mutations. We reported previously that unlike the BRICHOS misfolding SFTPC mutants, expression of hSP-C(I73T) induces lung remodeling and alveolar lipoproteinosis without a substantial Endoplasmic Reticulum (ER) stress response or ER-mediated intrinsic apoptosis.

A novel conserved targeting motif found in ABCA transporters mediates trafficking to early post-Golgi compartments.

The ATP binding cassette, class A (ABCA) proteins are homologous polytopic transmembrane transporters that function as lipid pumps at distinct subcellular sites in a variety of cells. Located within the N terminus of these transporters, there exists a highly conserved xLxxKN motif of unknown function. To define its role, human ABCA3 was employed as a primary model representing ABCA transporters, while mouse ABCA1 was utilized to support major findings.

Misfolded BRICHOS SP-C mutant proteins induce apoptosis via caspase-4- and cytochrome c-related mechanisms.

Several mutations within the BRICHOS domain of surfactant protein C (SP-C) have been linked to interstitial lung disease. Recent studies have suggested that these mutations cause misfolding of the proprotein (proSP-C), which initiates the unfolded protein response to resolve improper folding or promote protein degradation. We have reported that in vitro expression of one of these proteins, the exon 4 deletion mutant (hSP-C(Deltaexon4)), causes endoplasmic reticulum (ER) stress, inhibits proteasome function, and activates caspase-3-mediated apoptosis.