{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nNAPSB, representing the napsin B gene, has been characterized as a transcribed pseudogene that differs markedly from its functional counterpart napsin A. In one study, differential expression patterns between pronapsin A and B were documented in both lung tissue and various immune cell populations. While pronapsin A maintained steady mRNA levels in lung epithelium and lung carcinomas, the pronapsin B gene—despite being actively transcribed in lymphocytes, natural killer cells, and other immune cells—was notably down-regulated in terminally differentiated alveolar macrophages. This reciprocal regulation in myeloid cells hints at a potential role for NAPSB in the differentiation processes of immune cells and may serve as a complementary marker in the cellular context of lung pathology."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nEvolutionary analyses have further refined our understanding of NAPSB. Comparative genomic studies indicate that napsin B originated from a duplication event of napsin A during early primate evolution. Unlike napsin A, the napsin B gene has been undergoing pseudogenization, as it lacks a proper in-frame stop codon, leading to co-translational degradation of its nascent peptide. Notably, a rare single-nucleotide polymorphism is capable of restoring a stop codon, and recombinant expression coupled with structural modeling suggests that NAPSB retains residual enzymatic activity toward synthetic aspartic protease substrates—potentially attributed to a unique arginine residue."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nMoreover, recent clinical investigations have implicated NAPSB in the tumor microenvironment. In pancreatic ductal adenocarcinoma, for instance, NAPSB expression has been associated with CD4⁺ T cell infiltration, suggesting a link between this pseudogene and immune cell dynamics in malignancy. However, its functional role in other cancers, such as hepatocellular carcinoma, remains to be elucidated."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Matthew Cook, Frank Bühling, Siegfried Ansorge, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Pronapsin A and B gene expression in normal and malignant human lung and mononuclear blood cells."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biochim Biophys Acta (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/s0167-4781(02)00400-1"}], "href": "https://doi.org/10.1016/s0167-4781(02"}, {"type": "t", "text": "00400-1) PMID: "}, {"type": "a", "children": [{"type": "t", "text": "12151090"}], "href": "https://pubmed.ncbi.nlm.nih.gov/12151090"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Kazuhisa Nishishita, Eiko Sakai, Kuniaki Okamoto, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Structural and phylogenetic comparison of napsin genes: the duplication, loss of function and human-specific pseudogenization of napsin B."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Gene (2013)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.gene.2013.01.013"}], "href": "https://doi.org/10.1016/j.gene.2013.01.013"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23333608"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23333608"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Yu-Mei Ning, Kun Lin, Xiao-Ping Liu, et al. "}, {"type": "b", "children": [{"type": "t", "text": "NAPSB as a predictive marker for prognosis and therapy associated with an immuno-hot tumor microenvironment in hepatocellular carcinoma."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "BMC Gastroenterol (2022)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1186/s12876-022-02475-8"}], "href": "https://doi.org/10.1186/s12876-022-02475-8"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "35987606"}], "href": "https://pubmed.ncbi.nlm.nih.gov/35987606"}]}]}]}