title: Mesotrypsin Signature Mutation in a Chymotrypsin C (CTRC) Variant Associated with Chronic Pancreatitis.
abstract: Human chymotrypsin C (CTRC) protects against pancreatitis by degrading trypsinogen and thereby curtailing harmful intra-pancreatic trypsinogen activation. Loss-of-function mutations in CTRC increase the risk for chronic pancreatitis. Here we describe functional analysis of eight previously uncharacterized natural CTRC variants tested for potential defects in secretion, proteolytic stability, and catalytic activity. We found that all variants were secreted from transfected cells normally, and none suffered proteolytic degradation by trypsin. Five variants had normal enzymatic activity, whereas variant p.R29Q was catalytically inactive due to loss of activation by trypsin and variant p.S239C exhibited impaired activity possibly caused by disulfide mispairing. Surprisingly, variant p.G214R had increased activity on a small chromogenic peptide substrate but was markedly defective in cleaving bovine β-casein or the natural CTRC substrates human cationic trypsinogen and procarboxypeptidase A1. Mutation p.G214R is analogous to the evolutionary mutation in human mesotrypsin, which rendered this trypsin isoform resistant to proteinaceous inhibitors and conferred its ability to cleave these inhibitors. Similarly to the mesotrypsin phenotype, CTRC variant p.G214R was inhibited poorly by eglin C, ecotin, or a CTRC-specific variant of SGPI-2, and it readily cleaved the reactive-site peptide bonds in eglin C and ecotin. We conclude that CTRC variants p.R29Q, p.G214R, and p.S239C are risk factors for chronic pancreatitis. Furthermore, the mesotrypsin-like CTRC variant highlights how the same natural mutation in homologous pancreatic serine proteases can evolve a new physiological role or lead to pathology, determined by the biological context of protease function.
authors.affiliation: From the Department of Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts 02118.
authors.forename: András
authors.initials: A
authors.lastname: Szabó
authors.affiliation: From the Department of Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts 02118, Pediatric Nutritional Medicine and Else Kröner-Fresenius-Zentrum (EKFZ) für Ernährungsmedizin, Technische Universität München (TUM), 85350 Munich, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Ludwig
authors.affiliation: the Second Department of Pediatrics, Comenius University Faculty of Medicine in Bratislava, University Children's Hospital in Bratislava, 833 40 Bratislava, Slovakia, and.
authors.forename: Eszter
authors.initials: E
authors.lastname: Hegyi
authors.affiliation: the Clinic of Children and Adolescents, Comenius University Jessenius Faculty of Medicine in Martin, Martin University Hospital, 036 01 Martin, Slovakia.
authors.forename: Renata
authors.initials: R
authors.lastname: Szépeová
authors.affiliation: Pediatric Nutritional Medicine and Else Kröner-Fresenius-Zentrum (EKFZ) für Ernährungsmedizin, Technische Universität München (TUM), 85350 Munich, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Witt
authors.affiliation: From the Department of Molecular and Cell Biology, Boston University Henry M. Goldman School of Dental Medicine, Boston, Massachusetts 02118, miklos@bu.edu.
authors.forename: Miklós
authors.initials: M
authors.lastname: Sahin-Tóth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014644:Genetic Variation; D057809:HEK293 Cells; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D050500:Pancreatitis, Chronic / Q000201:enzymology* / Q000235:genetics*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012307:Risk Factors; D013379:Substrate Specificity; D014357:Trypsin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014362:Trypsinogen / Q000737:chemistry / Q000378:metabolism
chemical_list: D002364:Caseins; D011994:Recombinant Proteins; D014362:Trypsinogen; D002918:Chymotrypsin; C117569:chymotrypsin C; C040749:PRSS3 protein, human; D014357:Trypsin
keywords: chronic pancreatitis; chymotrypsin C; mesotrypsin; pancreas; protease inhibitor; serine protease; serine protease inhibitor; trypsin