Rationale: Mutations in the SFTPC gene, encoding surfactant protein C (SP-C), are associated with interstitial lung disease (ILD). Knowledge of the intracellular fate of mutant SP-C is essential for the design of therapies to correct trafficking/processing of the proprotein and prevent formation of cytotoxic aggregates.Objectives: To assess the potential of a chemical chaperone to correct trafficking and processing of three disease-associated, mutant SP-C proteins. Methods: HEK293 cells were stably transfected with wild type (SP-C(WT)) or mutant (SP-C(L188Q), SP-C(exon4 ) or SP-C(I73T)) SP-C and cell lines with similar expression of SP-C mRNA identified. The effect of the chemical chaperone 4-Phenylbutyric acid (PBA) and lysosomotropic drugs on the intracellular trafficking to the endolysosomal pathway and subsequent conversion of SP-C proprotein to mature peptide was assessed.Measurements and Main Results: Despite comparable SP-C mRNA expression, proprotein levels varied greatly: SP-C(I73T) was more abundant than SP-C(WT) and localized to the cell surface whereas SP-C(exon4 ) was barely detectable; in contrast, SP-C(L188Q) and SP-C(WT) proprotein levels were comparable and a small amount of SP-C(L188Q) was localized to the endolysosomal pathway. PBA treatment restored trafficking and processing of SP-C(L188Q) to SP-C(WT) levels but did not correct mistrafficking of SP-C(I73T) or rescue SP-C(exon4). PBA treatment also promoted aggregation of SP-C proproteins, including SP-C(L188Q).Conclusions: This study provides proof-of principle that a chemical chaperone can correct the mistrafficking and processing of a disease-associated mutant SP-C proprotein.
|Journal||American Journal of Respiratory Cell and Molecular Biology|
|Publication status||Published - 2012|