Cathepsin C, an important lysosomal cysteine protease, mediates the maturation process of neutrophil serine proteases, and participates in the inflammation and immune regulation process associated with polymorphonuclear neutrophils. Therefore, cathepsin C is considered to be an attractive target for treating inflammatory diseases. With INS1007 (trade name: brensocatib) being granted a breakthrough drug designation by FDA for the treatment of Adult Non-cystic Fibrosis Bronchiectasis and Coronavirus Disease 2019, the development of cathepsin C inhibitor will attract attentions from medicinal chemists in the future soon. Here, we summarized the research results of cathepsin C as a therapeutic target, focusing on the development of cathepsin C inhibitor, and provided guidance and reference opinions for the upcoming development boom of cathepsin C inhibitor.

OBJECTIVE: 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.
CONCLUSIONS: Our data support the molecular mechanism of PLS and enlarge the scope of CTSC gene mutations related to PLS.

OBJECTIVE: This study aims to investigate the gene mutational characteristics of cathepsin C (CTSC) gene in a Chinese patient with Papillon-Lefèvre syndrome (PLS), then further confirm the genetic basis for the phenotype of PLS, and obtain genetic information that can be used as guide in the diagnosis and treatment of PLS.
METHODS: With their consent, peripheral blood samples were obtained from the proband and his family members (his parents and older sister) for genomic DNA extraction. The coding region and exon/intron boundaries of the CTSC gene were amplified and sequenced using poly-merase chain reaction and direct sequencing of DNA.
RESULTS: Compound heterozygous mutations of CTSC gene were iden-tified in the patient. The proband carries one heterozygous nonsense mutation c.754C>T in exon 5 and one heterozygous missense mutation c.1040A>G in exon 7. Both parents were heterozygous carriers without the clinical symptoms of PLS. None of the mutations were detected in the proband\'s sister.
CONCLUSIONS: The study proves that mutations of CTSC gene are responsible for the phenotype of Papillon-Lefèvre syndrome.
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目的 通过研究一例掌跖角化-牙周破坏综合征（PLS）患者及其家系组织蛋白酶C（CTSC）基因突变的特点，提供PLS分子致病机制的理论依据，丰富PLS基因诊断和治疗的科学资料。方法 取得临床发现的一例PLS先证者及其家属知情同意，分别提取先证者及其父母、姐姐的基因组DNA，应用聚合酶链反应和DNA直接测序技术，分析先证者及其直系血亲CTSC基因的突变情况。结果 PLS先证者CTSC基因存在复合型杂合突变，突变位点是c.754C>T和c.1040A>G，其父母均为携带者，姐姐未发现突变。结论 PLS先证者的临床表征是由CTSC基因突变引起。.

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.
CONCLUSIONS: The c.901G>A mutation of the CTSC gene was first reported in China, which has expanded its mutation spectrum.

Papillon-Lefèvre syndrome (PLS) (OMIM: 245000) is a rare disease characterized by severe periodontitis and palmoplantar keratoderma. It is caused by mutations in both alleles of the cathepsin C (CatC) gene CTSC that completely abrogate the proteolytic activity of this cysteine proteinase. Most often, a genetic analysis to enable early and rapid diagnosis of PLS is unaffordable or unavailable. In this study, we tested the hypothesis that active CatC is constitutively excreted and can be easily traced in the urine of normal subjects. If this is true, determining its absence in the urine of patients would be an early, simple, reliable, low-cost and easy diagnostic technique. All 75 urine samples from healthy control subjects (aged 3 months to 80 years) contained proteolytically active CatC and its proform, as revealed by kinetic analysis and immunochemical detection. Of the urine samples of 31 patients with a PLS phenotype, 29 contained neither proteolytically active CatC nor the CatC antigen, so that the PLS diagnosis was confirmed. CatC was detected in the urine of the other two patients, and genetic analysis revealed no loss-of-function mutation in CTSC, indicating that they suffer from a PLS-like condition but not from PLS. Screening for the absence of urinary CatC activity soon after birth and early treatment before the onset of PLS manifestations will help to prevent aggressive periodontitis and loss of many teeth, and should considerably improve the quality of life of PLS patients.

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.
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.
CONCLUSIONS: 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.

Papillon-Lefèvre syndrome (PLS) is an autosomal recessive disease, characterized by severe periodontitis and palmoplantar hyperkeratosis. Mutations in the cathepsin C (CTSC) gene are the causative genetic factor. PLS starts at very early age, however, the age associated change of PLS has never been characterized. In this report, four PLS patients with CTSC mutations were followed up for seven years, periodontal condition and serum immunoglobulins (Igs) were recorded. Results showed that periodontal inflammation of PLS peaked at teenage years, but declined with time. At the same time the serum IgE change was consistent with the change, suggesting the possibility of using IgE as a monitoring index for PLS inflammation level, or to develop new target for therapy.

暂无摘要。

Papillon-Lefèvre syndrome (PLS) is a very rare syndrome of autosomal recessive inheritance characterized by palmoplantar hyperkeratosis and a severe destructive periodontitis, leading to premature loss of both primary and permanent dentitions. This article reported a boy who was diagnosed as having PLS.

OBJECTIVE: To investigate the mutational characteristics of the cathepsin C gene (CTSC, also known as dipeptidyl-peptidase I gene, DPP I) in a family of Han nationality with Papillon-Lefevre syndrome, and to provide the molecular basis for the phenotype.
METHODS: Genomic DNAs were extracted from the proband, his parents and younger sister after informed consent. Polymerase chain reaction and direct DNA sequencing were carried out to screen the mutations of the cathepsin C gene.
RESULTS: Compound heterozygous mutations of the cathepsin C gene were identified in the patient. The patient carried one frameshift mutation 116delG in exon 1, one heterozygous mutation C255S in exon 6, one missense mutation F314S and one sense mutation E335E in exon 7. The four changes were novel mutations of the cathepsin C gene, which had not been reported previously. None of the mutations were detected in normal controls.
CONCLUSIONS: Mutations of the cathepsin C gene are probably responsible for the phenotype of Papillon-Lefevre syndrome in this family.