A novel human chymotrypsin-like digestive enzyme

Genetic and functional analysis of chymotrypsin-like protease (CTRL) in chronic pancreatitis

BACKGROUND

Genetic predisposition is crucial in the pathogenesis of early-onset chronic pancreatitis (CP). So far, several genetic alterations have been identified as risk factors, predominantly in genes encoding digestive enzymes. However, many early-onset CP cases have no identified underlying cause. Chymotrypsins are a family of serine proteases that can cleave trypsinogen and lead to its degradation. Because genetic alterations in the chymotrypsins CTRC, CTRB1, and CTRB2 are associated with CP, we genetically and functionally investigated chymotrypsin-like protease (CTRL) as a potential risk factor.

METHODS

We screened 1005 non-alcoholic CP patients and 1594 controls for CTRL variants by exome sequencing. We performed Western blots and activity assays to analyse secretion and proteolytic activity. We measured BiP mRNA expression to investigate the potential impact of identified alterations on endoplasmic reticulum (ER) stress.

RESULTS

We identified 13 heterozygous non-synonymous CTRL variants: five exclusively in patients and three only in controls. Functionality was unchanged in 6/13 variants. Four alterations showed normal secretion but reduced (p.G20S, p.G56S, p.G61S) or abolished (p.S208F) activity. Another three variants (p.C201Y, p.G215R and p.C220G) were not secreted and already showed reduced or no activity intracellularly. However, intracellular retention did not lead to ER stress.

CONCLUSION

We identified several CTRL variants, some showing potent effects on protease function and secretion. We observed these effects in variants found in patients and controls, and CTRL loss-of-function variants were not significantly more common in patients than controls. Therefore, CTRL is unlikely to play a relevant role in the development of CP.

Substrate specificity of human chymotrypsin-like protease (CTRL) characterized by phage display-selected small-protein inhibitors

Chymotrypsin-like protease (CTRL) is one of the four chymotrypsin isoforms expressed in the human exocrine pancreas. Human genetic and experimental evidence indicate that chymotrypsins B1, B2, and C (CTRB1, CTRB2 and CTRC) are important not only for protein digestion but also for protecting the pancreas against pancreatitis by degrading potentially harmful trypsinogen. CTRL has not been reported to play a similar role, possibly due to its low abundance and/or different substrate specificity. To address this problem, we investigated the specificity of the substrate-binding groove of CTRL by evolving the substrate-like canonical loop of the Schistocerca gregaria proteinase inhibitor 2 (SGPI-2), a small-protein reversible chymotrypsin inhibitor to bind CTRL. We found that phage-associated SGPI-2 variants with strong affinity to CTRL were similar to those evolved previously against CTRB1, CTRB2 or bovine chymotrypsin A (bCTRA), indicating comparable substrate specificity. When tested as recombinant proteins, SGPI-2 variants inhibited CTRL with similar or slightly weaker affinity than bCTRA, confirming that CTRL is a typical chymotrypsin. Interestingly, an SGPI-2 variant selected with a Thr29His mutation in its reactive loop was found to inhibit CTRL strongly, but it was digested rapidly by bCTRA. Finally, CTRL was shown to degrade human anionic trypsinogen, however, at a much slower rate than CTRB2, suggesting that CTRL may not have a significant role in the pancreatic defense mechanisms against inappropriate trypsinogen activation and pancreatitis.

Diet evolution of carnivorous and herbivorous mammals in Laurasiatheria

Background

Laurasiatheria contains taxa with diverse diets, while the molecular basis and evolutionary history underlying their dietary diversification are less clear.

Results

In this study, we used the recently developed molecular phyloecological approach to examine the adaptive evolution of digestive system-related genes across both carnivorous and herbivorous mammals within Laurasiatheria. Our results show an intensified selection of fat and/or protein utilization across all examined carnivorous lineages, which is consistent with their high-protein and high-fat diets. Intriguingly, for herbivorous lineages (ungulates), which have a high-carbohydrate diet, they show a similar selection pattern as that of carnivorous lineages. Our results suggest that for the ungulates, which have a specialized digestive system, the selection intensity of their digestive system-related genes does not necessarily reflect loads of the nutrient components in their diets but appears to be positively related to the loads of the nutrient components that are capable of being directly utilized by the herbivores themselves. Based on these findings, we reconstructed the dietary evolution within Laurasiatheria, and our results reveal the dominant carnivory during the early diversification of Laurasiatheria. In particular, our results suggest that the ancestral bats and the common ancestor of ruminants and cetaceans may be carnivorous as well. We also found evidence of the convergent evolution of one fat utilization-related gene, APOB, across carnivorous taxa.

Conclusions

Our molecular phyloecological results suggest that digestive system-related genes can be used to determine the molecular basis of diet differentiations and to reconstruct ancestral diets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-02033-6.

Arg236 in human chymotrypsin B2 (CTRB2) is a key determinant of high enzyme activity, trypsinogen degradation capacity, and protection against pancreatitis

Pancreatic chymotrypsins (CTRs) are digestive proteases that in humans include CTRB1, CTRB2, CTRC, and CTRL. The highly similar CTRB1 and CTRB2 are the products of gene duplication. A common inversion at the CTRB1-CTRB2 locus reverses the expression ratio of these isoforms in favor of CTRB2. Carriers of the inversion allele are protected against the inflammatory disorder pancreatitis presumably via their increased capacity for CTRB2-mediated degradation of harmful trypsinogen. To reveal the protective molecular determinants of CTRB2, we compared enzymatic properties of CTRB1, CTRB2, and bovine CTRA (bCTRA). By evolving substrate-like Schistocerca gregaria proteinase inhibitor 2 (SGPI-2) inhibitory loop variants against the chymotrypsins, we found that the substrate binding groove of the three enzymes had overlapping specificities. Based on the selected sequences, we produced eight SGPI-2 variants. Remarkably, CTRB2 and bCTRA bound these inhibitors with significantly higher affinity than CTRB1. Moreover, digestion of peptide substrates, beta casein, and human anionic trypsinogen unequivocally confirmed that CTRB2 is a generally better enzyme than CTRB1 while the potency of bCTRA lies between those of the human isoforms. Unexpectedly, mutation D236R alone converted CTRB1 to a CTRB2-like high activity protease. Modeling indicated that in CTRB1 Met210 partially obstructed the substrate binding groove, which was relieved by the D236R mutation. Taken together, we identify CTRB2 Arg236 as a key positive determinant, while CTRB1 Asp236 as a negative determinant for chymotrypsin activity. These findings strongly support the concept that in carriers of the CTRB1-CTRB2 inversion allele, the superior trypsinogen degradation capacity of CTRB2 protects against pancreatitis.

Trypsinogen and chymotrypsinogen: potent anti-tumor agents

Introduction: Trypsinogen and chymotrypsinogen have been used clinically in tissue repair due to their ability to resolve inflammatory symptoms. Recently, novel evidence has supported the anti-tumourigenic potential of a mixture of trypsinogen and chymotrypsinogen.Areas covered: First, we analyze the structure of these proteases and the effects of pancreatic proteinases on tissue repair, inflammation and the immune system. Second, we summarize studies that provided evidence of the effects of pancreatic (pro)enzymes on tumor cells both in vitro and in vivo and some successful clinical applications of pancreatic (pro)enzymes. Finally, we study pancreatic (pro)enzymes potential molecular targets, such as the proteinase-activated receptors (PARs).Expert opinion: This novel therapy has been shown to have effective antitumor effects. Treatment with these (pro) enzymes sensitizes Cancer Stem Cells (CSCs) which may allow chemotherapy and radiotherapy to be more effective, which could positively affect the recovery of cancer patients.

Loss of chymotrypsin-like protease (CTRL) alters intrapancreatic protease activation but not pancreatitis severity in mice

The digestive enzyme chymotrypsin protects the pancreas against pancreatitis by reducing harmful trypsin activity. Genetic deficiency in chymotrypsin increases pancreatitis risk in humans and pancreatitis severity in mice. Pancreatic chymotrypsin is produced in multiple isoforms including chymotrypsin B1, B2, C and chymotrypsin-like protease (CTRL). Here we investigated the role of CTRL in cerulein-induced pancreatitis in mice. Biochemical experiments with recombinant mouse enzymes demonstrated that CTRL cleaved trypsinogens and suppressed trypsin activation. We generated a novel CTRL-deficient strain (Ctrl-KO) using CRISPR-Cas9 genome engineering. Homozygous Ctrl-KO mice expressed no detectable CTRL protein in the pancreas. Remarkably, the total chymotrypsinogen content in Ctrl-KO mice was barely reduced indicating that CTRL is a low-abundance isoform. When given cerulein, Ctrl-KO mice exhibited lower intrapancreatic chymotrypsin activation and a trend for higher trypsin activation, compared with C57BL/6N mice. Despite the altered protease activation, severity of cerulein-induced acute pancreatitis was similar in Ctrl-KO and C57BL/6N mice. We conclude that CTRL is a minor chymotrypsin isoform that plays no significant role in cerulein-induced pancreatitis in mice.

Expression Profile of the Digestive Enzymes of Manis javanica Reveals Its Adaptation to Diet Specialization

The expression of animal digestive enzymes reflects important dietary adaptations. The pangolin, also known as scaly anteater, is a specialized myrmecophage that consumes mainly ants and termites, but its digestive enzymes have not been fully investigated. Therefore, in this study, we used shotgun proteomic analysis to examine the protein components of the saliva and intestinal juice of a Sunda pangolin (Manis javanica) that died shortly after being rescued. The intestinal juice contained greater variety of digestive enzymes, including α-amylase, maltase-glucoamylase, α,α-trehalase, sucrase-isomaltase, pepsin A, trypsin, pancreatic endopeptidase E, carboxypeptidase A1, carboxypeptidase B, dipeptidyl-peptidase 4, and pancreatic triacylglycerol lipase. The digestive enzymes identified in the saliva were maltase-glucoamylase and trypsin, and chitinase which was also found in the intestinal juice. Compared with other animals, the Sunda pangolin has less intestinal protease diversity and lacks key digestive enzymes, such as chymotrypsin and pancreatic elastase. The expression profile of the digestive enzymes of the Sunda pangolin reveals animal's adaptation to a diet consisting mainly of ants and termites. Our results will facilitate the preparation of artificial food for rescued pangolins and for those in captivity for conservation breeding efforts.

Chymotrypsin Reduces the Severity of Secretagogue-Induced Pancreatitis in Mice

Intrapancreatic activation of the digestive proteases trypsin and chymotrypsin is an early event in the development of pancreatitis. Human genetic studies indicate that chymotrypsin controls trypsin activity via degradation, but there is no evidence of this from animal models. We used CRISPR-Cas9 to disrupt the chymotrypsinogen B1 gene (Ctrb1) in C57BL/6N mice and induced pancreatitis in CTRB1-deficient and C57BL/6N (control) mice by administration of cerulein. CTRB1-deficient mice given cerulein had significant increases in intrapancreatic trypsin activity and developed more severe pancreatitis compared with control mice. CTRB1 therefore protects against secretagogue-induced pancreatitis by reducing trypsin activity. Protease inhibitors developed for treatment of pancreatitis should be designed to target trypsin but not chymotrypsin.

Scandinavian Journal of Gastroenterology - the editors-in-chief

The SJG has enjoyed a sequence of active and dynamic editors-in-chief following the initial period with Professor Myren in charge. This paper gives a short overview of the subsequent editors including their clinical and scientific merits.

Human pancreatic digestive enzymes

A primary function of the pancreas is to produce digestive enzymes that are delivered to the small intestine for the hydrolysis of complex nutrients. Much of our understanding of digestive enzymes comes from studies in animals. New technologies and the availability of the sequence of the human genome allow for a critical review of older reports and assumptions based on animal studies. This report updates our understanding of human pancreatic digestive enzymes with a focus on new insights into the biology of human proteases, lipases and amylases.

Identification of biomarkers of human pancreatic adenocarcinomas by expression profiling and validation with gene expression analysis in endoscopic ultrasound-guided fine needle aspiration samples

AIM: To compare gene expression profiles of pancreatic adenocarcinoma tissue specimens, human pancreatic and colon adenocarcinoma and leukemia cell lines and normal pancreas samples in order to distinguish differentially expressed genes and to validate the differential expression of a subset of genes by quantitative real-time RT-PCR (RT-QPCR) in endoscopic ultrasound-guided fine needle aspiration (EUS-guided FNA) specimens.

METHODS: Commercially dedicated cancer cDNA macroarrays (Atlas Human Cancer 1.2) containing 1176 genes were used. Different statistical approaches (hierarchical clustering, principal component analysis (PCA) and SAM) were used to analyze the expression data. RT-QPCR and immunohistochemical studies were used for validation of results.

RESULTS: RT-QPCR validated the increased expression of LCN2 (lipocalin 2) and for the first time PLAT (tissue-type plasminogen activator or tPA) in malignant pancreas as compared with normal pancreas. Immunohistochemical analysis confirmed the increased expression of LCN2 protein localized in epithelial cells of ducts invaded by carcinoma. The analysis of PLAT and LCN2 transcripts in 12 samples obtained through EUS-guided FNA from patients with pancreatic adenocarcinoma showed significantly increased expression levels in comparison with those found in normal tissues, indicating that a sufficient amount of high quality RNA can be obtained with this technique.

CONCLUSION: Expression profiling is a useful method to identify biomarkers and potential target genes. Molecular analysis of EUS-guided FNA samples in pancreatic cancer appears as a valuable strategy for the diagnosis of pancreatic adenocarcinomas.

A novel serine protease highly expressed in the pancreas is expressed in various kinds of cancer cells

We have isolated a cDNA that encodes a novel serine protease, prosemin, from human brain. The cDNA of human prosemin is 1306 bp, encoding 317 amino acids. It showed significant homology with the sequence of a chromosome 16 cosmid clone (accession no. NT_037887.4). The prosemin gene contains six exons and five introns. The amino acid sequence of prosemin shows significant homology to prostasin, gamma-tryptase, and testisin (43%, 41%, and 38% identity, respectively), the genes of which are also located on chromosome 16. Northern hybridization showed that prosemin is expressed predominantly in the pancreas and weakly in the prostate and cerebellum. However, western blot and RT-PCR analyses showed that prosemin is expressed and secreted from various kinds of cancer cells, such as glioma, pancreas, prostate, and ovarian cell lines. Prosemin is secreted in the cystic fluid of clinical ovarian cancers. Furthermore, immunohistochemistry showed prosemin protein localized in the apical parts of ovarian carcinomas. Recombinant prosemin was expressed in COS cells and was purified by immunoaffinity chromatography. Recombinant prosemin preferentially cleaved benzyloxycarbonyl (Z)-His-Glu-Lys-methylcoumaryl amidide (MCA) and t-butyloxycarbonyl (Boc)-Gln-Ala-Arg-MCA. Our results suggest that prosemin is a novel serine protease of the chromosome 16 cluster that is highly expressed in the pancreas. The usefulness of this serine protease as a candidate tumor marker should be further examined.

Characterization of PSKH1, a novel human protein serine kinase with centrosomal, golgi, and nuclear localization

We report here the characterization of PSKH1, a novel human protein serine kinase with multiple intracellular localizations. The gene consists of three exons distributed over 35 kb of genomic DNA in region 16q22.1. The 3.4-kb cDNA predicts a protein of 424 amino acids with a calculated molecular mass of 48.1 kDa and pI of 9.6. PSKH1 is expressed in all tissues and cell lines tested as shown by Northern blots, with the highest level of abundance in testis. PSKH1 displays the highest level of similarity with rat CaM kinase I (50. 2%) over 259 amino acids in the conserved catalytic region, but lacks significant homology with proteins in the database outside the catalytic core. Polyclonal antibodies have been raised, and indirect immunofluorescence microscopy of untransfected COS-1 cells suggests that PSKH1 is localized in the Brefeldin A-sensitive Golgi compartment, at centrosomes, in the nucleus with a somewhat speckle-like presence, and more diffusely in the cytoplasm. The presence in the centrosome appears to be enhanced during osmotic stress. Immunoisolated PSKH1 does not phosphorylate any of the common kinase substrates in vitro, but autophosphorylates exclusively serines within its COOH-terminal region in an intermolecular fashion. Furthermore, autophosphorylation activity is repressed upon addition of Ca(2+)/CaM, suggesting that PSKH1 activity depends on Ca(2+) concentration in vivo.

The differential specificity of chymotrypsin A and B is determined by amino acid 226

The A and B isoforms of the pancreatic serine proteinase, chymotrypsin are known to cleave substrates selectively at peptide bonds formed by some hydrophobic residues, like tryptophan, phenylalanine and tyrosine. We found, however, that the B forms of native bovine and recombinant rat chymotrypsins are two orders of magnitude less active on the tryptophanyl than on the phenylalanyl or tyrosyl substrates, while bovine chymotrypsin A cleaves all these substrates with comparable catalytic efficiency. Analysing the structure of substrate binding pocket of chymotrypsin A prompted us to perform an Ala226Gly substitution in rat chymotrypsin B. The specificity profile of the Ala226Gly rat chymotrypsin B became similar to that of bovine chymotrypsin A suggesting that only the amino acid at sequence position 226 is responsible for the differential specificities of chymotrypsin A and B isoenzymes.