Cathepsin C in health and disease: from structural insights to therapeutic prospects.

Cathepsin C (CTSC) is a lysosomal cysteine protease constitutively expressed at high levels in the lung, kidney, liver, and spleen. It plays a key role in the activation of serine proteases in cytotoxic T cells, natural killer cells (granzymes A and B), mast cells (chymase and tryptase) and neutrophils (cathepsin G, neutrophil elastase, proteinase 3) underscoring its pivotal significance in immune and inflammatory defenses. Here, we comprehensively review the structural attributes, synthesis, and function of CTSC, with a focus on its variants implicated in the etiopathology of several syndromes associated with neutrophil serine proteases, including Papillon-Lefevre syndrome (PLS), Haim-Munk Syndrome (HMS), and aggressive periodontitis (AP). These syndromes are characterized by palmoplantar hyperkeratosis, and early-onset periodontitis (severe gum disease) resulting in premature tooth loss. Due to the critical role played by CTSC in these and several other conditions it is being explored as a potential therapeutic target for autoimmune and inflammatory disorders. The review also discusses in depth the gene variants of CTSC, and in particular their postulated association with chronic obstructive pulmonary disease (COPD), COVID-19, various cancers, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, sudden cardiac death (SCD), atherosclerotic vascular disease, and neuroinflammatory disease. Finally, the therapeutic potential of CTSC across a range of human diseases is discussed.

"Oral Manifestations of Patients with Inherited Defect in Phagocyte Number or Function" a systematic review.

INTRODUCTION: Inherited phagocyte defects are one of the subgroups of primary immunodeficiency diseases (PIDs) with various clinical manifestations. As oral manifestations are common at the early ages, oral practitioners can have a special role in the early diagnosis. MATERIALS AND METHODS: A comprehensive search was conducted in this systematic review study and data of included studies were categorized into four subgroups of phagocyte defects, including congenital neutropenia, defects of motility, defects of respiratory burst, and other non-lymphoid defects. RESULTS: Among all phagocyte defects, 12 disorders had reported data for oral manifestations in published articles. A total of 987 cases were included in this study. Periodontitis is one of the most common oral manifestations. CONCLUSION: There is a need to organize better collaboration between medical doctors and dentists to diagnose and treat patients with phagocyte defects. Regular dental visits and professional oral health care are recommended from the time of the first primary teeth eruption in newborns.

Palmoplantar keratoderma, oral involvement, and homozygous CTSC mutation in two brothers from Cambodia.

Haim-Munk syndrome (HMS) and Papillon-Lefevre syndrome (PLS) are phenotypic variants of palmoplantar keratoderma (PPK) with progressive early-onset periodontitis and dental caries. HMS and PLS have been associated with homozygous or compound heterozygous mutations in the lysosomal protease gene Cathepsin C (CTSC). There have been only a few documented cases of CTSC mutations in patients from South-East Asia. We report the clinical findings of two Cambodian brothers who presented with diffuse, demarcated PPK with transgrediens extending to the elbows and knees, as well as pachyonychia and dental caries. Arachnodactyly and periodontitis were also found in the older brother. Next-generation sequencing unveiled a homozygous missense variant in CTSC (NM_001814.5: c.1337AC: p.(Asp446Ala)) in both brothers. Both parents were heterozygous for the variant, while an unaffected older brother was homozygous for the wild-type allele. Our study adds to the spectrum of mutations and associated clinical presentations for this rare genodermatosis.

Papillon-Lefèvre syndrome (PLS) with novel compound heterozygous mutation in the exclusion and Peptidase C1A domains of Cathepsin C gene.

Papillon Lefevre syndrome (PLS) manifests with palmoplantar keratoderma, combined with a rapidly progressive periodontitis associated with mutations in Cathepsin C (CTSC) gene. This article reports a 15-year old male proband with typical PLS traits having a novel compound heterozygote with p.Q49X mutation in exon 1 and p.Y259C missense mutation in exon 6 of CTSC gene respectively. The exon 1 mutation, p.Q49X, (found in proband's mother) was located in exclusion domain and exon 6 mutation, p.Y259C (found in proband's father), was present in peptidase C1A, papain C-terminal domain. Interestingly, missense mutation p.Y259C identified in this study was found to be not reported so far. Upon computational analysis, this missense mutation was found to be lethal. Moreover, our protein modelling approach using mutant protein revealed the presence of monomeric structure on contrary to the tetrameric structure of the wild type protein. In addition, in vitro functional characterization of mutant p.Y259C expressed in HEK293 cells showed a significant reduction in CTSC activity (0.015 ± 0.009 mU/ml) when compared with wild type protein (0.21 ± 0.008 mU/ml). Thus, in this study, we have demonstrated that the pathogenic missense mutant p.Y259C might cause PLS by impaired CTSC function.

Papillon-Lefèvre syndrome: Oral aspects and treatment.

Papillon-Lefèvre syndrome (PLS) is a rare disorder characterized by diffuse palmoplantar erythematous, fissured hyperkeratosis, and aggressive periodontal disease that starts in the early periods of childhood. Periodontal disease occurs with the early loss of deciduous teeth at the age of 2 to 4 years, followed by the loss of permanent teeth during adolescence. Prosthodontics management of PLS patients is very complex and sometimes requires invasive therapeutic treatments. Early diagnosis is essential for correct treatment management avoiding the possibility that patients are early edentulous. Management could be a conventional periodontal treatment and pharmacological therapy but in severe cases, digital techniques, could be help the clinician for increased patient comfort and minimized tissue damage.

Identification of putative genetic modifying factors that influence the development of Papillon-Lefévre or Haim-Munk syndrome phenotypes.

BACKGROUND: Papillon-Lefévre syndrome (PLS; OMIM 245000) and Haim-Munk syndrome (HMS; OMIM 245010), which are both characterized by palmoplantar hyperkeratosis and periodontitis, are phenotypic variants of the same disease caused by mutations of the cathepsin C (CTSC) gene. AIM: To identify putative genetic modifying factors responsible for the differential development of the PLS or HMS phenotypes, we investigated two Hungarian patients with different phenotypic variants (PLS and HMS) but carrying the same homozygous nonsense CTSC mutation (c.748C/T; p.Arg250X). METHODS: To gain insights into phenotype-modifying associations, whole exome sequencing (WES) was performed for both patients, and the results were compared to identify potentially relevant genetic modifying factors. RESULTS: WES revealed two putative phenotype-modifying variants: (i) a missense mutation (rs34608771) of the SH2 domain containing 4A (SH2D4A) gene encoding an adaptor protein involved in intracellular signalling of cystatin F, a known inhibitor of the cathepsin protein, and (ii) a missense variant (rs55695858) of the odorant binding protein 2A (OBP2A) gene, influencing the function of the cathepsin protein through the glycosyltransferase 6 domain containing 1 (GLT6D1) protein. CONCLUSION: Our study contributes to the accumulating evidence supporting the clinical importance of phenotype-modifying genetic factors, which have high potential to aid the elucidation of genotype-phenotype correlations and disease prognosis.

Clinical and molecular analysis in Papillon-Lefèvre syndrome.

Papillon-Lefèvre syndrome (PLS; MIM#245000) is a rare recessive autosomal disorder characterized by palmar and plantar hyperkeratosis, and aggressively progressing periodontitis leading to premature loss of deciduous and permanent teeth. PLS is caused by loss-of-function mutations in the CTSC gene, which encodes cathepsin C. PLS clinical expressivity is highly variable and no consistent genotype-phenotype correlation has been demonstrated yet. Here we report the clinical and genetic features of five PLS patients presenting a severe periodontal breakdown in primary and permanent dentition, hyperkeratosis over palms and soles, and recurrent sinusitis and/or tonsillitis. Mutation analysis revealed two novel homozygous recessive mutations (c.947T>C and c.1010G>C) and one previous described homozygous recessive mutation (c.901G>A), with parents carrying them in heterozygous, in three families (four patients). The fourth family presented with the CTSC c.628C>T mutation in heterozygous, which was inherited maternally. Patient carrying the CTSC c.628C>T mutation featured classical PLS phenotype, but no PLS clinical characteristics were found in his carrier mother. All mutations were found to affect directly (c.901G>A, c.947T>C, and c.1010G>C) or indirectly (c.628C>T, which induces a premature termination) the heavy chain of the cathepsin C, the region responsible for activation of the lysosomal protease. Together, these findings indicate that both homozygous and heterozygous mutations in the cathepsin C heavy chain domain may lead to classical PLS phenotype, suggesting roles for epistasis or gene-environment interactions on determination of PLS phenotypes.

CTSC compound heterozygous mutations in two Chinese patients with Papillon-Lefèvre syndrome.

OBJECTIVES: To identify the molecular basis of Papillon-Lefèvre syndrome in two Chinese families. METHODS: Peripheral blood and mouth swab samples were obtained, from which genomic DNA and RNA were isolated. Sanger sequencing was employed to identify the mutations. mRNA expression was tested by real-time quantitative PCR. Evolutionary conservation, pathogenicity prediction and impact of protein structures of the mutations were conducted with bioinformatics tools and homology modelling. HEK293 cells were transfected with plasmids expressing wild-type or mutated CTSC. CTSC protein expression level and enzyme activity were explored. RESULTS: Mutation analysis revealed two novel compound heterozygous mutations, the c.190-191insA and c.1211-1212delA in patient 1 and the c.716A>G and c.757+1G>A in patient 2. In both patients, the levels of CTSC mRNA were significantly lower than in their relatives. Homology modelling analysis predicted that the mutations affect the structure and stability of the protein, and in vitro study showed that the CTSC proteins containing the mutations c.190-191insA and c.1211-1212delA, which result in truncated versions of protein, display impaired enzyme activity. The protein containing c.716A>G mutation showed quite similar enzyme activity compared to wild-type CTSC. CONCLUSION: Our data support the molecular mechanism of PLS and enlarge the scope of CTSC gene mutations related to PLS.

Autophagic dysfunction in patients with Papillon-Lefèvre syndrome is restored by recombinant cathepsin C treatment.

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.

Oro-dental characteristics of three siblings with Papillon-Lefevre syndrome.

Papillon-Lefevre syndrome (PLS) is a rare autosomal recessive disorder, showing oral and dermatological manifestations in the form of aggressive periodontitis, leading to the premature loss of both primary and permanent teeth at a very young age and palmar-plantar hyperkeratosis. It was first described by two French physicians, Papillon and Lefevre in 1924. Immunologic, genetic, or possible bacterial etiologies have been thought to account for etiopathogenesis of PLS. Severe gingival inflammation and periodontal destruction occurred after the eruption of primary teeth. This condition should warn the physicians and dentists as a one of the important sign for the diagnosis of PLS. There have been over 250 cases reported in literature about PLS, but a few of these were in the same family. This study presents oro-dental characteristics, dental treatments, and follow-up of three siblings (age of sisters are 13, 6, and 4 years) with PLS, which is rarely seen in the same family.

A novel large deletion combined with a nonsense mutation in a Chinese child with Papillon-Lefèvre syndrome.

BACKGROUND AND OBJECTIVE: Papillon-Lefèvre Syndrome (PLS) is a rare autosomal recessive hereditary disease (MIM245000). The syndrome is characterized by palmoplantar keratoderma and early onset periodontitis, caused by CTSC gene mutation. The mutation in CTSC previously reported is mainly point mutations. Large deletion in the CTSC gene has not yet been reported. MATERIAL AND METHODS: We collected 5 mL peripheral blood from a patient with PLS and her family members and used the direct sequencing method to perform CTSC bidirectional sequencing. We also used FISH to analyze the approximate locations of the ends of the missing fragment and then determined the fragment sequence through direct sequencing. RESULTS: The result demonstrated that the patient have a 110 kb deletion (Chr11: 88032292: 88142997(NC_000011)) combined with a nonsense mutation (Gln182Ter) in this gene. CONCLUSION: Our study reveals a compound mutation consisting of a large deletion and a nonsense mutation, which provides a new insight in the mutation type of CTSC gene.

One mutation, two phenotypes: a single nonsense mutation of the CTSC gene causes two clinically distinct phenotypes.

BACKGROUND: Papillon-Lefévre syndrome (PLS; OMIM 245000) and Haim-Munk syndromes (HMS; OMIM 245010) are phenotypic variants of the same rare disease caused by mutations of the cathepsin C (CTSC) gene, and they exhibit autosomal recessive inheritance. AIMS: To identify diseases caused by mutations of the CTSC gene in two Hungarian patients and to perform haplotype analysis to elucidate any familial relationship between them. METHODS: Mutation screening and polymorphism analysis were performed by direct sequencing of the CTSC gene. RESULTS: Mutation screening of the CTSC gene from the two patients revealed the presence of the same homozygous nonsense mutation (c.748C/T; p.Arg250X). However, one patient exhibited the PLS phenotype and the other the HMS phenotype. Although these patients were not aware that they were related, haplotype analysis, especially the genotypes of the rs217116 and the rs217115 polymorphisms, clearly indicated that the patients carry the same haplotype, whereas the unrelated healthy controls carried several different haplotypes. CONCLUSIONS: Our results demonstrate that PLS and HMS are phenotypic variants of the same disease and, additionally, exclude the presence of a putative genetic modifier factor within the CTSC gene that is responsible for the development of the two phenotypes. We suggest that this putative genetic modifier factor is located outside the CTSC gene, or alternatively, that the development of the different phenotypes is the consequence of different environmental or lifestyle factors.

[Screening of CTSC gene mutations in a Chinese pedigree affected with Papillon-Lefevre syndrome].

OBJECTIVE: To analyze the clinical phenotype of a Chinese pedigree affected with Papillon-Lefevre syndrome(PLS) and detect mutation of CTSC gene. METHODS: Clinical phenotypes were noted, and oral examination for the proband was carried out for the clinical diagnosis of PLS. PCR and Sanger sequencing were used to identify potential mutation of the CTSC gene. Functional effect of the mutation was predicted with SIFT and PolyPhen-2. Swiss-Port was used to predict the tertiary structure of wild type and mutant proteins. The mRNA and protein expression were analyzed by real-time PCR and Western blotting. RESULTS: A homozygous mutation c.901G>A (p.G301S) in exon 7 of CTSC gene was identified in the patient. Both parents of the patient had carried a heterozygous c.901G>A mutation. The mutation was located in the conserved region of CTSC enzyme and was predicted to be damaging by changing the structure of the protein, which could affect the activity of Cathepsin C. However, no significant difference was found in the expression of p.G301S variant at the mRNA and protein levels compared with that of the wild type CTSC gene. CONCLUSION: The c.901G>A mutation of the CTSC gene was first reported in China, which has expanded its mutation spectrum.

NSP4 is stored in azurophil granules and released by activated neutrophils as active endoprotease with restricted specificity.

Whereas neutrophil elastase, cathepsin G, and proteinase 3 have been known as granule-associated serine proteases of neutrophils for decades, a fourth member, called neutrophil serine protease 4 (NSP4), was just recently described and provisionally characterized. In this study, we identified NSP4 as a novel azurophil granule protein of neutrophils by Western blot analyses of subcellular fractions as well as by RT-PCR analyses of neutrophil precursors from human bone marrow. The highest mRNA levels were observed in myeloblasts and promyelocytes, similar to myeloperoxidase, a marker of azurophil granules. To determine the extended sequence specificity of recombinant NSP4, we used an iterative fluorescence resonance energy transfer-based optimization strategy. In total, 142 different peptide substrates with arginine in P1 and variations at the P1', P2', P3, P4, and P2 positions were tested. This enabled us to construct an α1-proteinase inhibitor variant (Ile-Lys-Pro-Arg-/-Ser-Ile-Pro) with high specificity for NSP4. This tailor-made serpin was shown to form covalent complexes with all NSP4 of neutrophil lysates and supernatants of activated neutrophils, indicating that NSP4 is fully processed and stored as an already activated enzyme in azurophil granules. Moreover, cathepsin C was identified as the activator of NSP4 in vivo, as cathepsin C deficiency resulted in a complete absence of NSP4 in a Papillon-Lefèvre patient. Our in-depth analysis of NSP4 establishes this arginine-specific protease as a genuine member of preactivated serine proteases stored in azurophil granules of human neutrophils.

Papillon-Lefèvre syndrome with homozygous nonsense mutation of cathepsin C gene presenting with late-onset periodontitis.

Papillon-Lefèvre syndrome (PLS) is a rare autosomal recessive disorder of keratinization caused by homozygous mutations in the gene encoding lysosomal protease cathepsin C (CTSC). It is clinically characterized by transgredient palmoplantar keratoderma (PPK) and periodontitis. A 15-year-old boy presenting with PPK from the age of 6 months and late-onset periodontitis that began at the age of 12 years is described. Mutation analysis revealed a homozygous nonsense mutation (p.Y304X) in exon 7 of the CTSC gene. Late-onset periodontitis in a patient with Papillon-Lefèvre syndrome is a rare phenotypic variation.

Systemic lupus erythematosus complicated with liver cirrhosis in a patient with Papillon-Lefèvre syndrome.

We report the first case of a girl who presented with Papillon-Lefèvre syndrome (PLS) and subsequently developed systemic lupus erythematosus and liver cirrhosis. This indicates that autoimmune diseases can be a complication in patients with PLS. Cathepsin C gene mutations were not found in our patient or her mother. Thus, other genetic factors may have been involved in this patient.