title: 4-Phenylbutyric acid treatment rescues trafficking and processing of a mutant surfactant protein-C.
abstract: 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 in the design of therapies to correct trafficking/processing of the proprotein, and to prevent the formation of cytotoxic aggregates. We assessed the potential of a chemical chaperone to correct the trafficking and processing of three disease-associated mutant SP-C proteins. HEK293 cells were stably transfected with wild-type (SP-C(WT)) or mutant (SP-C(L188Q), SP-C(Δexon4), or SP-C(I73T)) SP-C, and cell lines with a similar expression of SP-C mRNA were identified. The effects of the chemical chaperone 4-phenylbutyric acid (PBA) and lysosomotropic drugs on intracellular trafficking to the endolysosomal pathway and the subsequent conversion of SP-C proprotein to mature peptide were assessed. Despite comparable SP-C mRNA expression, proprotein concentrations varied greatly: SP-C(I73T) was more abundant than SP-C(WT) and was localized to the cell surface, whereas SP-C(Δexon4) was barely detectable. In contrast, SP-C(L188Q) and SP-C(WT) proprotein concentrations were comparable, and a small amount of SP-C(L188Q) was localized to the endolysosomal pathway. PBA treatment restored the trafficking and processing of SP-C(L188Q) to SP-C(WT) concentrations, but did not correct the mistrafficking of SP-C(I73T) or rescue SP-C(Δexon4). PBA treatment also promoted the aggregation of SP-C proproteins, including SP-C(L188Q). This study provides proof of the principle that a chemical chaperone can correct the mistrafficking and processing of a disease-associated mutant SP-C proprotein.
authors.affiliation: Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC7029, Cincinnati, OH 45229-3039, USA.
authors.forename: Gareth A
authors.initials: GA
authors.lastname: Stewart
authors.forename: Ross
authors.initials: R
authors.lastname: Ridsdale
authors.forename: Emily P
authors.initials: EP
authors.lastname: Martin
authors.forename: Cheng-Lun
authors.initials: CL
authors.lastname: Na
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.forename: Karunyakanth
authors.initials: K
authors.lastname: Mandapaka
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Weaver
mesh_terms: D002460:Cell Line; D003902:Detergents / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009154:Mutation; D010654:Phenylbutyrates / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D037721:Pulmonary Surfactant-Associated Protein C / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D012995:Solubility
chemical_list: D003902:Detergents; D010654:Phenylbutyrates; D037721:Pulmonary Surfactant-Associated Protein C; D012333:RNA, Messenger; C075773:4-phenylbutyric acid