Secretagogue-induced pancreatitis in mice devoid of chymotrypsin.

The serine protease chymotrypsin protects the pancreas against pancreatitis by degrading trypsinogen, the precursor to the digestive protease trypsin. Taking advantage of previously generated mouse models with either the Ctrb1 gene (encoding chymotrypsin B1) or the Ctrl gene (encoding chymotrypsin-like protease) disrupted, here we generated the novel Ctrb1-del × Ctrl-KO strain in the C57BL/6N genetic background, which harbors a naturally inactivated Ctrc gene (encoding chymotrypsin C). The newly created mice are devoid of chymotrypsin, yet the animals develop normally, breed well, and show no spontaneous phenotype, indicating that chymotrypsin is dispensable under laboratory conditions. When given cerulein, the Ctrb1-del × Ctrl-KO strain exhibited markedly increased intrapancreatic trypsin activation and more severe acute pancreatitis, relative to wild-type C57BL/6N mice. After the acute episode, Ctrb1-del × Ctrl-KO mice spontaneously progressed to chronic pancreatitis, whereas C57BL/6N mice recovered rapidly. The cerulein-induced pancreas pathology in Ctrb1-del × Ctrl-KO mice was highly similar to that previously observed in Ctrb1-del mice; however, trypsin activation was more robust and pancreatitis severity was increased. Taken together, the results confirm and extend prior observations demonstrating that chymotrypsin safeguards the pancreas against pancreatitis by limiting pathologic trypsin activity. In mice, the CTRB1 isoform, which constitutes about 90% of the total chymotrypsin content, is responsible primarily for the anti-trypsin defenses and protection against pancreatitis; however, the minor isoform CTRL also contributes to an appreciable extent.NEW & NOTEWORTHY Chymotrypsins defend the pancreas against the inflammatory disorder pancreatitis by degrading harmful trypsinogen. This study demonstrates that mice devoid of pancreatic chymotrypsins are phenotypically normal but become sensitized to secretagogue hyperstimulation and exhibit increased intrapancreatic trypsin activation, more severe acute pancreatitis, and rapid progression to chronic pancreatitis. The observations confirm and extend the essential role of chymotrypsins in pancreas health.

Abamectin exposure causes chronic toxicity and trypsin/chymotrypsin damages in Chironomus kiiensis Tokunaga (Diptera: Chironomidae).

Abamectin has been extensively used in paddy fields to control insect pests. However, little information is available regarding its effects on non-target insects. In this study, we performed acute (3rd instar larvae) and chronic toxicity (newly hatched larvae <24 h) to determine the toxicity effects of abamectin on Chironomus kiiensis. The median lethal concentration (LC50) values of 24 h and 10 d were 0.57 mg/L and 68.12 µg/L, respectively. The chronic exposure significantly prolonged the larvae growth duration and inhibited pupation and emergence. The transcriptome and biochemical parameters were measured using 3rd instar larvae exposed to acute LC10 and LC25 for 24 h. Transcriptome data indicated that five trypsin and four chymotrypsin genes were downregulated, and RT-qPCR verified a significant expression decrease in trypsin3 and chymotrypsin1 genes. Meanwhile, abamectin could significantly inhibit the activities of the serine proteases trypsin and chymotrypsin. RNA interference showed that silencing trypsin3 and chymotrypsin1 genes led to higher mortality of C. kiiensis to abamectin. In conclusion, these findings indicated that trypsin and chymotrypsin are involved in the abamectin toxicity against C. kiiensis, which provides new insights into the mechanism of abamectin-induced ecotoxicity to chironomids.

Bowman-Birk Inhibitor Mutants of Soybean Generated by CRISPR-Cas9 Reveal Drastic Reductions in Trypsin and Chymotrypsin Inhibitor Activities.

Despite the high quality of soybean protein, raw soybeans and soybean meal cannot be directly included in animal feed mixtures due to the presence of Kunitz (KTi) and Bowman-Birk protease inhibitors (BBis), which reduces animal productivity. Heat treatment can substantially inactivate trypsin and chymotrypsin inhibitors (BBis), but such treatment is energy-intensive, adds expense, and negatively impacts the quality of seed proteins. As an alternative approach, we have employed CRISPR/Cas9 gene editing to create mutations in BBi genes to drastically lower the protease inhibitor content in soybean seed. Agrobacterium-mediated transformation was used to generate several stable transgenic soybean events. These independent CRISPR/Cas9 events were examined in comparison to wild-type plants using Sanger sequencing, proteomic analysis, trypsin/chymotrypsin inhibitor activity assays, and qRT-PCR. Collectively, our results demonstrate the creation of an allelic series of loss-of-function mutations affecting the major BBi gene in soybean. Mutations in two of the highly expressed seed-specific BBi genes lead to substantial reductions in both trypsin and chymotrypsin inhibitor activities.

Novel chymotrypsin C (CTRC) variants from real-world genetic testing of pediatric chronic pancreatitis cases.

BACKGROUND: Chymotrypsin C (CTRC) protects the pancreas against unwanted intrapancreatic trypsin activity through degradation of trypsinogen. Loss-of-function CTRC variants increase the risk for chronic pancreatitis (CP). The aim of the present study was to characterize novel CTRC variants found during genetic testing of CP cases at a pediatric pancreatitis center. METHODS: We used next-generation sequencing to screen patients. We analyzed the functional effects of CTRC variants in HEK 293T cells and using purified enzymes. RESULTS: In 5 separate cases, we detected 5 novel heterozygous CTRC variants: c.407C>T (p.Thr136Ile), c.550G>A (p.Ala184Thr), c.627Cdup (p.Ser210Leufs∗?, where the naming indicates a frame shift with no stop codon), c.628T>C (p.Ser210Pro), and c.779A>G (p.Asp260Gly). Functional studies revealed that with the exception of p.Ser210Leufs∗?, the CTRC variants were secreted normally from transfected cells. Enzyme activity of purified variants p.Thr136Ile, p.Ala184Thr, and p.Asp260Gly was similar to that of wild-type CTRC, whereas variant p.Ser210Pro was inactive. The frame-shift variant p.Ser210Leufs∗? was not secreted but accumulated intracellularly, and induced endoplasmic reticulum stress, as judged by elevated mRNA levels of HSPA5 and DDIT3, and increased mRNA splicing of XBP1. CONCLUSIONS: CTRC variants p.Ser210Pro and p.Ser210Leufs∗? abolish CTRC function and should be classified as pathogenic. Mechanistically, variant p.Ser210Pro directly affects the amino acid at the bottom of the substrate-binding pocket while the frame-shift variant promotes misfolding and thereby blocks enzyme secretion. Importantly, 3 of the 5 novel CTRC variants proved to be benign, indicating that functional analysis is indispensable for reliable determination of pathogenicity and the correct interpretation of genetic test results.

Pathogen-associated molecular patterns (PAMPs) derived from Leishmania and bacteria increase gene expression of antimicrobial peptides and gut surface proteins in sand flies.

The interaction between pathogens and vectors' physiology can impact parasite transmission. Studying this interaction at the molecular level can help in developing control strategies. We study leishmaniases, diseases caused by Leishmania parasites transmitted by sand fly vectors, posing a significant global public health concern. Lipophosphoglycan (LPG), the major surface glycoconjugate of Leishmania, has been described to have several roles throughout the parasite's life cycle, both in the insect and vertebrate hosts. In addition, the sand fly midgut possesses a rich microbiota expressing lipopolysaccharides (LPS). However, the effect of LPG and LPS on the gene expression of sand fly midgut proteins or immunity effectors has not yet been documented. We experimentally fed Lutzomyia longipalpis and Phlebotomus papatasi sand flies with blood containing purified LPG from Leishmania infantum, Leishmania major, or LPS from Escherichia coli. The effect on the expression of genes encoding gut proteins galectin and mucin, digestive enzymes trypsin and chymotrypsin, and antimicrobial peptides (AMPs) attacin and defensins was assessed by quantitative PCR (qPCR). The gene expression of a mucin-like protein in L. longipalpis was increased by L. infantum LPG and E. coli LPS. The gene expression of a galectin was increased in L. longipalpis by L. major LPG, and in P. papatasi by E. coli LPS. Nevertheless, the gene expression of trypsins and chymotrypsins did not significantly change. On the other hand, both L. infantum and L. major LPG significantly enhanced expression of the AMP attacin in both sand fly species and defensin in L. longipalpis. In addition, E. coli LPS increased the expression of attacin and defensin in L. longipalpis. Our study showed that Leishmania LPG and E. coli LPS differentially modulate the expression of sand fly genes involved in gut maintenance and defence. This suggests that the glycoconjugates from microbiota or Leishmania may increase the vector's immune response and the gene expression of a gut coating protein in a permissive vector.

Heliothis virescens chymotrypsin is translationally controlled by AeaTMOF binding ABC putative receptor.

Heliothis virescens larval chymotrypsin (GenBank accession number AF43709) was cloned, sequenced and its three dimensional (3D) conformation modeled. The enzyme's transcript was first detected 6 days after larval emergence and the transcript level was shown to fall between larval ecdysis periods. Comparisons between the activities of larval gut chymotrypsin and trypsin shows that chymotrypsin activity is only 16% of the total trypsin activity and the pH optimum of the larval chymotrypsin is between pH 9-10, however the enzyme also exhibited a broad activity between pH 4-6. Injections of AeaTMOF and several shorter analogues into 3rd instar larvae followed by Northern blot analyses showed that although the chymotrypsins activities were inhibited by 60%-80% the transcript level of the sequenced chymotrypsin was not reduced and was similar to controls in which the chymotrypsin activity was not inhibited, indicating that AeaTMOF and its analogues exert a translational control. Based on these observations a putative AeaTMOF receptor (ABCC4) homologous to the Ae. aegypti ABC receptor sequence was found in the H. virescens genome. 3D molecular modeling and docking of the AeaTMOF and several of its analogues to the ABCC4 receptor showed that it can bind AeaTMOF and its analogues as was shown before for the Ae. aegypti receptor.

Risk of chronic pancreatitis in carriers of the c.180C>T (p.Gly60=) CTRC variant: case-control studies and meta-analysis.

Chymotrypsin C (CTRC) is a digestive serine protease produced by the pancreas that regulates intrapancreatic trypsin activity and provides a defensive mechanism against chronic pancreatitis (CP). CTRC exerts its protective effect by promoting degradation of trypsinogen, the precursor to trypsin. Loss-of-function missense and microdeletion variants of CTRC are found in around 4% of CP cases and increase disease risk by approximately 3-7-fold. In addition, a commonly occurring synonymous CTRC variant c.180C>T (p.Gly60=) was reported to increase CP risk in various cohorts but a global analysis of its impact has been lacking. Here, we analyzed the frequency and effect size of variant c.180C>T in Hungarian and pan-European cohorts, and performed meta-analysis of the new and published genetic association data. When allele frequency was considered, meta-analysis revealed an overall frequency of 14.2% in patients and 8.7% in controls (allelic odds ratio (OR) 2.18, 95% confidence interval (CI) 1.72-2.75). When genotypes were examined, c.180TT homozygosity was observed in 3.9% of CP patients and in 1.2% of controls, and c.180CT heterozygosity was present in 22.9% of CP patients and in 15.5% of controls. Relative to the c.180CC genotype, the genotypic OR values were 5.29 (95% CI 2.63-10.64), and 1.94 (95% CI 1.57-2.38), respectively, indicating stronger CP risk in homozygous carriers. Finally, we obtained preliminary evidence that the variant is associated with reduced CTRC mRNA levels in the pancreas. Taken together, the results indicate that CTRC variant c.180C>T is a clinically relevant risk factor, and should be considered when genetic etiology of CP is investigated.

Cloning and characterization of Aedes aegypti blood downregulated chymotrypsin II.

Aedes aegypti adult and larval blood downregulated chymotrypsin II was cloned, sequenced and its 3D conformation modeled. Cloning of the enzymes from adult and larval guts indicated that both genes sit at the same location on Chromosome 2. Genomic analyses showed that larval and adult genes are the same and both have four exons and three introns that are located on an 8.32 Kb DNA in direction with the Ae. aegypti genome. The adult and larval transcript synthesis is controlled by alternative splicing explaining small difference in the amino acids sequences. Chymotrypsin II that was extracted from guts of sugar-fed and at 48 after blood feeding showed a pH optimum of 4-5 with a broad shoulder of activity from pH 6 to 10. Dot blot analyses show that the enzyme's transcript is downregulated after females take a blood meal and upregulated at 48 h after the blood meal. A Chymotrypsin II transcript was also detected in the larval gut during different times of larval developmental stages, indication that Ae. aegypti chymotrypsin II is synthesized by adults and larval guts. The possibility that JH III and 20HE play an active role in the regulation is discussed.

Mouse model of PRSS1 p.R122H-related hereditary pancreatitis highlights context-dependent effect of autolysis-site mutation.

Mutation p.R122H in human cationic trypsinogen (PRSS1) is the most frequently identified cause of hereditary pancreatitis. The mutation blocks protective degradation of trypsinogen by chymotrypsin C (CTRC), which involves an obligatory trypsin-mediated cleavage at Arg122. Previously, we found that C57BL/6N mice are naturally deficient in CTRC, and trypsinogen degradation is catalyzed by chymotrypsin B1 (CTRB1). Here, we used biochemical experiments to demonstrate that the cognate p.R123H mutation in mouse cationic trypsinogen (isoform T7) only partially prevented CTRB1-mediated degradation. We generated a novel C57BL/6N mouse strain harboring the p.R123H mutation in the native T7 trypsinogen locus. T7R123H mice developed no spontaneous pancreatitis, and severity parameters of cerulein-induced pancreatitis trended only slightly higher than those of C57BL/6N mice. However, when treated with cerulein for 2 days, more edema and higher trypsin activity was seen in the pancreas of T7R123H mice compared to C57BL/6N controls. Furthermore, about 40% of T7R123H mice progressed to atrophic pancreatitis in 3 days, whereas C57BL/6N animals showed full histological recovery. Taken together, the observations indicate that mutation p.R123H inefficiently blocks chymotrypsin-mediated degradation of mouse cationic trypsinogen, and modestly increases cerulein-induced intrapancreatic trypsin activity and pancreatitis severity. The findings support the notion that the pathogenic effect of the PRSS1 p.R122H mutation in hereditary pancreatitis is dependent on its ability to defuse chymotrypsin-dependent defenses.

Localization and pathogenic role of the cysteine protease dentipain in Treponema denticola.

The Msp protein complex and the serine protease dentilisin are the best-characterized virulence factors in Treponema denticola, the major etiological agent of chronic periodontitis. In addition to these outer sheath factors, the cysteine protease dentipain contributes to pathogenicity, but its secretion, processing, cellular localization, and role in T. denticola virulence are not fully understood. In this study, we found that full-sized dentipain (74-kDa) and the 52-kDa truncated form of the enzyme are located, respectively, in the outer sheath derived from T. denticola dentilisin- and the Msp-deficient mutants. Furthermore, dentipain was barely detected in the wild-type strain. These results suggest that dentilisin and Msp, the major outer sheath proteins, are involved in the secretion and maturation of dentipain. Inactivation of the dentipain gene slowed the growth of T. denticola, and the effect was more profound in serum-free medium than in serum-containing medium. Several genes, including those encoding transporters and methyl-accepting chemotaxis proteins, were differentially expressed in the dentipain-deficient mutant. Furthermore, the mutant strain was more hydrophobic than the wild-type strain. Finally, the mutant showed less autoaggregation activity and adhesion to IgG in a serum-free medium than the wild-type strain. These findings suggest that dentipain contributes to the virulence of T. denticola by facilitating adhesion and acquisition of nutrients essential for colonization and proliferation in the gingival crevice under serum-rich conditions.

Up-regulated serpin gene involved in Cry1Ac resistance in Helicoverpa armigera.

Insect resistance to Bacillus thuringiensis (Bt) is a critical limiting factor for applying the Bt crops. Some studies indicated that decreased protoxin activation because of lower enzymatic activities of trypsin and chymotrypsin and increased expression of serpin might involve in Bt resistance. Our previous study identified an endogenous serpin could inhibit the midgut proteases to activate Cry1Ac and reduce the insecticide activity to Helicoverpa armigera. We hypothesis that up-regulated serpin involve in resistance via inhibiting enzymatic activities of trypsin and chymotrypsin to decrease protoxin activation. Herein, we found the serpin-e gene relative expression in midgut was significantly higher in the LF30 resistant strain than that in the susceptible strain during all developmental stages. Importantly, RNAi-mediated silencing of serpin-e gene expression caused 4.46-fold mortality changes in LF30 strain, but the trypsin and chymotrypsin proteases activities were only changed 0.79-fold and 2.22-fold. In addition, although proteases activities were significantly lower in LF30 strain than that in the susceptible strain, the resistance ratios of LF30 to Cry1Ac protoxin and to activated Cry1Ac toxin were no difference. The results indicated serpins caused insect resistance to Cry1Ac protoxins partly through inhibiting the trypsin and chymotrypsin proteases activities, but it also existed other mechanisms in LF30.

Adaptation of Helicoverpa armigera to Soybean Peptidase Inhibitors Is Associated with the Transgenerational Upregulation of Serine Peptidases.

Molecular phenotypes induced by environmental stimuli can be transmitted to offspring through epigenetic inheritance. Using transcriptome profiling, we show that the adaptation of Helicoverpa armigera larvae to soybean peptidase inhibitors (SPIs) is associated with large-scale gene expression changes including the upregulation of genes encoding serine peptidases in the digestive system. Furthermore, approximately 60% of the gene expression changes induced by SPIs persisted in the next generation of larvae fed on SPI-free diets including genes encoding regulatory, oxidoreductase, and protease functions. To investigate the role of epigenetic mechanisms in regulating SPI adaptation, the methylome of the digestive system of first-generation larvae (fed on a diet with and without SPIs) and of the progeny of larvae exposed to SPIs were characterized. A comparative analysis between RNA-seq and Methyl-seq data did not show a direct relationship between differentially methylated and differentially expressed genes, while trypsin and chymotrypsin genes were unmethylated in all treatments. Rather, DNA methylation potential epialleles were associated with transcriptional and translational controls; these may play a regulatory role in the adaptation of H. armigera to SPIs. Altogether, our findings provided insight into the mechanisms of insect adaptation to plant antiherbivore defense proteins and illustrated how large-scale transcriptional reprograming of insect genes can be transmitted across generations.

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.

Identification and expression profiling of serine protease-related genes in Tenebrio molitor.

In insects, serine proteases and serine protease homologs (SPs/SPHs) are involved in a variety of physiological processes including digestion, development, and immunity. Here, we identified 112 SP and 88 SPH genes in the genome of the yellow mealworm, Tenebrio molitor. Based on the features of domain structure, they were divided into "S" group containing single Tryp-SPc or Tryp-SPHc domain, "C" group containing 1-4 CLIP domain (CLIPA-D) and "M" group containing the CBD, CUB, EGF, Fz, Gd, LDLa, PAN, SEA, SR, Sushi, and TSP domains, and have 115, 48, and 37 gene members, respectively. According to the active sites in the catalytic triad, the putative trypsin, chymotrypsin, or elastase-like enzyme specificity of the identified SPs/SPHs were predicted. Phylogenetic and genomic location analyses revealed that gene duplication exists in the large amount of SPs/SPHs. Gene expression profiling using RNA-seq data along with real time reverse transcription-polymerase chain reaction analysis showed that most SP/SPH genes display life stage specific expression patterns, indicating their important roles in development. Many SP/SPH genes are specifically or highly expressed in the gut, salivary gland, fat body, hemocyte, ovary, and testis, suggesting that they participate in digestion, immunity, and reproduction. The findings lay the foundation for further functional characterization of SPs/SPHs in T. molitor.

Loss-of-function variant in chymotrypsin like elastase 3B (CELA3B) is associated with non-alcoholic chronic pancreatitis.

BACKGROUND: Genetic alterations in digestive enzymes have been associated with chronic pancreatitis (CP). Recently, chymotrypsin like elastase 3B (CELA3B) emerged as a novel risk gene. Thus, we evaluated CELA3B in two European cohorts with CP. METHODS: We analyzed all 8 CELA3B exons in 550 German non-alcoholic CP (NACP) patients and in 241 German controls by targeted DNA sequencing. In addition, we analyzed exons 6 and 7 by Sanger sequencing and the c.129+1G>A variant by melting curve analysis in 1078 further German controls. As replication cohort, we investigated up to 243 non-German European NACP patients and up to 1665 controls originating from Poland, Hungary, and Sweden. We assessed the cellular secretion and the elastase activity of recombinant CELA3B variants. RESULTS: In the German discovery cohort, we detected a splice-site variant in intron 2, c.129+1G>A, in 9/550 (1.64%) CP patients and in 5/1319 (0.38%) controls (P=0.007, OR=4.4, 95% CI=1.5-13.0). In the European replication cohort, this variant was also enriched in patients (9/178 [5.06%]) versus controls (13/1247 [1.04%]) (P=0.001, OR=5.1, 95% CI=2.1-12.0). We did not find the two previously reported codon 90 variants, p.R90C and p.R90L. CONCLUSIONS: Our data indicate that CELA3B is a susceptibility gene for CP. In contrast to previous reports suggesting that increased CELA3B activity is associated with CP risk, the splice-site variant identified here is predicted to cause diminished CELA3B expression. How reduced CELA3B function predisposes to pancreatitis remains to be elucidated.

Risk of chronic pancreatitis in carriers of loss-of-function CTRC variants: A meta-analysis.

The digestive protease chymotrypsin C (CTRC) protects the pancreas against pancreatitis by degrading potentially harmful trypsinogen. Loss-of-function genetic variants in CTRC increase risk for chronic pancreatitis (CP) with variable effect size, as judged by the reported odds ratio (OR) values. Here, we performed a meta-analysis of published studies on four variants that alter the CTRC amino-acid sequence, are clinically relatively common (global carrier frequency in CP >1%), reproducibly showed association with CP and their loss of function phenotype was verified experimentally. We found strong enrichment of CTRC variants p.A73T, p.V235I, p.K247_R254del, and p.R245W in CP cases versus controls, yielding OR values of 6.5 (95% confidence interval (CI) 2.4-17.8), 4.5 (CI 2.2-9.1), 5.4 (CI 2.6-11.0), and 2.6 (CI 1.6-4.2), respectively. Subgroup analysis demonstrated disease association of variants p.K247_R254del and p.R245W in alcoholic CP with similar effect sizes as seen in the overall CP group. Homozygosity or compound heterozygosity were rare and seemed to be associated with higher risk. We also identified a so far unreported linkage disequilibrium between variant p.K247_R254del and the common c.180C>T (p.G60 =) haplotype. Taken together, the results indicate that heterozygous loss-of-function CTRC variants increase the risk for CP approximately 3-7-fold. This meta-analysis confirms the clinical significance of CTRC variants and provides further justification for the genetic screening of CP patients.

Chymotrypsin is a molecular target of insect resistance of three corn varieties against the Asian corn borer, Ostrinia furnacalis.

The Asian corn borer, Ostrinia furnacalis, is a serious insect pest that can infest corn leaves and stems. Due to its internal feeding behavior, its larvae are not exposed to insecticides that are usually sprayed for pest control. To minimize crop damage caused by O. furnacalis, improving insect resistance trait of corn has been considered as an optimal control tactic. This study screened 27 corn varieties for their insect resistance trait and selected three varieties of Ilmichal (IM), P3394, and Kwangpyeongok (KP) that showed insect resistance trait. O. furnacalis larvae did not show any significant difference in preference between these three insect-resistant corn varieties and a control susceptible variety. However, these resistant varieties after ingestion significantly interfered with larval development of O. furnacalis. This suggests that the insect resistance trait is induced by antibiosis, but not by antixenosis. Indeed, larvae fed with these varieties suffered from low chymotrypsin (CHY) activities in the midgut juice. To determine the target CHY inhibited by resistant corn varieties, a total of nine CHY genes (Of-CHY1~Of-CHY9) were predicted from the transcriptome of O. furnacalis. Six genes (Of-CHY1~Of-CHY6) were expressed in all developmental stages and tissues. Especially, Of-CHY3 was highly expressed in the midgut of O. furnacalis larvae. RNA interference (RNAi) using double-stranded RNA (dsRNA) specific to Of-CHY3 (2 µg of dsRNA injected to each L5 larva) resulted in significant reduction of Of-CHY3 expression level at 24 h post-treatment. Feeding L3 larvae with this dsRNA also significantly suppressed the expression level of Of-CHY3 and reduced its enzyme activity at 24 h post-treatment. A recombinant Escherichia coli expressing dsRNA specific to Of-CHY3 was constructed using L4440 vector. Feeding such recombinant bacteria suppressed the expression level of Of-CHY3 and prevented larval development of O. furnacalis. These results suggest that the three resistant varieties can produce a resistance factor(s) to inhibit the CHY activity of O. furnacalis and suppress larval growth. This study suggests that CHY might be an inhibition target in O. furnacalis for breeding insect-resistant corns.

A 584 bp deletion in CTRB2 inhibits chymotrypsin B2 activity and secretion and confers risk of pancreatic cancer.

Genome-wide association studies (GWASs) have discovered 20 risk loci in the human genome where germline variants associate with risk of pancreatic ductal adenocarcinoma (PDAC) in populations of European ancestry. Here, we fine-mapped one such locus on chr16q23.1 (rs72802365, p = 2.51 × 10-17, OR = 1.36, 95% CI = 1.31-1.40) and identified colocalization (PP = 0.87) with aberrant exon 5-7 CTRB2 splicing in pancreatic tissues (pGTEx = 1.40 × 10-69, ßGTEx = 1.99; pLTG = 1.02 × 10-30, ßLTG = 1.99). Imputation of a 584 bp structural variant overlapping exon 6 of CTRB2 into the GWAS datasets resulted in a highly significant association with pancreatic cancer risk (p = 2.83 × 10-16, OR = 1.36, 95% CI = 1.31-1.42), indicating that it may underlie this signal. Exon skipping attributable to the deletion (risk) allele introduces a premature stop codon in exon 7 of CTRB2, yielding a truncated chymotrypsinogen B2 protein that lacks chymotrypsin activity, is poorly secreted, and accumulates intracellularly in the endoplasmic reticulum (ER). We propose that intracellular accumulation of a nonfunctional chymotrypsinogen B2 protein leads to ER stress and pancreatic inflammation, which may explain the increased pancreatic cancer risk in carriers of CTRB2 exon 6 deletion alleles.

Knockdown of Helicoverpa armigera protease genes affects its growth and mortality via RNA interference.

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), the cotton bollworm, is a destructive pest which is famous for its resistance to a variety of insecticides. RNA interference is a posttranscriptional gene silencing mechanism that has become a popular tool to control insect pests, triggered by double-stranded RNAs (dsRNAs). The effect of ingestion and injection delivery methods of dsRNA related to some protease genes including Trypsin (Ha-TRY39 and Ha-TRY96), Chymotrypsin (Ha-CHY), and Cathepsin L (Ha-CAT) on growth and development of H. armigera was investigated in this study. All protease genes encoded full ORFs and were expressed in all H. armigera larvae stages and tissues. In both injection and feeding bioassays, Ha-RNAi CHY's performance outperformed that of other protease genes. CHY enzyme activity in the midgut of larvae was significantly reduced after treatment with ds-HaCHY. Oral administration of ds-CHY also resulted in significant mortality of H. armigera larvae. However, because of the high RNase activity in the midgut lumen of lepidoptera, a large amount of dsRNA was needed to effectively kill instars of H. armigera. To reduce dsRNA degradation, bacterial expression and dsRNA formulation were used. After oral administration, it was toxic to H. armigera larvae. Before oral administration, bacterial cells were sonicated to increase dsRNA release. The RNA interference efficiency of sonicated bacteria was significantly increased, resulting in higher larval mortality when administered orally. All of these findings point to Ha-CHY as a new candidate for developing an effective dsRNA-based pesticide for H. armigera control.