Autophagic dysfunction in Papillon Lefèvre syndrome is restored by recombinant Cathepsin C treatment

Abstract

[Background]: Cathepsin C (CatC) is a lysosomal enzyme involved in activation of serine proteases from immune and inflammatory cells. Several loss-of-function mutations in the CatC gene have been shown to be the genetic mark of Papillon-Lefèvre syndrome (PLS), a rare autosomal recessive disease characterized by severe early-onset periodontitis, palmoplantar hyperkeratosis, and increased susceptibility to infections. Deficiencies or dysfunction in other cathepsin family proteins, such as cathepsin B or D, have been associated with autophagic and lysosomal disorders.

[Objectives]: Here we characterized the basis for autophagic dysfunction in patients with PLS by analyzing skin fibroblasts derived from patients with several mutations in the CatC gene and reduced enzymatic activity.

[Methods]: Skin fibroblasts were isolated from patients with PLS assessed by using genetic analysis. Authophagic flux dysfunction was evaluated by examining accumulation of p62/SQSTM1 and a bafilomycin assay. Ultrastructural analysis further confirmed abnormal accumulation of autophagic vesicles in mutant cells. A recombinant CatC protein was produced by a baculovirus system in insect cell cultures.

[Results]: Mutant fibroblasts from patients with PLS showed alterations in oxidative/antioxidative status, reduced oxygen consumption, and a marked autophagic dysfunction associated with autophagosome accumulation. These alterations were accompanied by lysosomal permeabilization, cathepsin B release, and NLR family pyrin domain containing 3 (NLRP3) inflammasome activation. Treatment of mutant fibroblasts with recombinant CatC improved cell growth and autophagic flux and partially restored lysosomal permeabilization.

[Conclusions]: Our data provide a novel molecular mechanism underlying PLS. Impaired autophagy caused by insufficient lysosomal function might represent a new therapeutic target for PLS.