Chymotrypsin C (CTRC) variants that diminish activity or secretion are associated with chronic pancreatitis

Abstract

Chronic pancreatitis is a persistent inflammatory disease of the pancreas. The digestive protease trypsin plays a fundamental role in the pathogenesis. Here we analyzed the gene encoding the trypsindegrading enzyme chymotrypsin C (CTRC) in German subjects with idiopathic or hereditary chronic pancreatitis. Two alterations, p.R254W and p.K247_R254del, were significantly overrepresented in the pancreatitis group and were present in 30/901 (3.3%) affected individuals but only in 21/2,804 (0.7%) controls (OR=4.6; CI=2.6−8.0; P=1.3×10 −7 ). A replication study identified these two variants in 10/348 (2.9%) individuals with alcoholic chronic pancreatitis but only in 3/432 (0.7%) subjects with alcoholic liver disease (OR=4.2; CI=1.2−15.5; P=0.02). CTRC variants were also found in 10/71 (14.1%) Indian subjects with tropical pancreatitis but only in 1/84 (1.2%) control (OR=13.6; CI=1.7 −109.2; P=0.0028). Functional analysis of the CTRC variants revealed impaired activity and/or reduced secretion. The results indicate that loss-of-function alterations in CTRC predispose to pancreatitis by diminishing its protective trypsin-degrading activity.Chronic pancreatitis is a continuing inflammatory disorder characterized by permanent destruction of the pancreatic parenchyma leading to maldigestion and diabetes mellitus due to exocrine and endocrine insufficiency. Penetrating insight into the pathomechanism came from relatively recent studies investigating the genes encoding cationic trypsinogen (PRSS1; OMIM 276000), anionic trypsinogen (PRSS2; OMIM 601564), and the pancreatic secretory trypsin inhibitor (SPINK1; OMIM 167790). Gain-of-function variants in PRSS1 have been linked to autosomal dominant hereditary pancreatitis and subsequently also to idiopathic chronic pancreatitis 1-4 . Recently, triplication of the PRSS1 locus has been observed in a subset of families with hereditary pancreatitis 5 . In vitro biochemical studies revealed that the majority of disease predisposing PRSS1 variants increase autocatalytic conversion of trypsinogen to active trypsin and probably promote premature intrapancreatic trypsin activation in vivo 6,7 . Consistent with the central pathophysiological role of trypsin, p.N34S and other loss-offunction alterations in the trypsin inhibitor SPINK1 predispose to idiopathic, tropical, and alcoholic chronic pancreatitis 8-15 . In contrast to pathogenic PRSS1 and SPINK1 variations, the p.G191R PRSS2 variant affords protection against chronic pancreatitis due to rapid autodegradation 16 . Taken together, genetic and biochemical evidence defines a pathological pathway in which a sustained imbalance between intrapancreatic trypsinogen activation and trypsin inactivation results in the development of chronic pancreatitis ( Supplementary Fig. 1).Because trypsin degradation serves as a protective mechanism against pancreatitis, we hypothesized that loss of function in trypsin degrading enzymes increases the risk for pancreatitis. We recently demonstrated that chymotrypsin C (CTRC) degrades all human tryps...

Tighter Control by Chymotrypsin C (CTRC) Explains Lack of Association between Human Anionic Trypsinogen and Hereditary Pancreatitis

“…The most common hereditary pancreatitis-associated mutations alter these cleavages resulting in more robust activation and higher trypsin levels (10). Even in the absence of trypsinogen mutations, the protective effect of CTRC against pancreatitis can be compromised by loss-of-function mutations in CTRC, which increase risk for sporadic chronic pancreatitis (31). As our mechanistic insight into how PRSS1 mutations cause hereditary pancreatitis advanced, the nagging question why PRSS2 mutations are not associated with the disease has remained unanswered.…”

Genetic Analysis of Human Chymotrypsin-Like Elastases 3A and 3B (CELA3A and CELA3B) to Assess the Role of Complex Formation between Proelastases and Procarboxypeptidases in Chronic Pancreatitis

“…Mutations in the best characterized risk genes PRSS1 (cationic trypsinogen), SPINK1 (pancreatic secretory trypsin inhibitor), and CTRC (chymotrypsin C) stimulate activation of trypsinogen and result in elevated trypsin activity in the pancreas [4][5][6][7][8][9]. More recently, loss-of-function variants in the CPA1 gene encoding carboxypeptidase A1 were shown to increase risk for early onset CP [10].…”

Relationship of strain-dependent susceptibility to experimentally induced acute pancreatitis with regulation of Prss1 and Spink3 expression

“…23 We earlier showed that Spink3 (mouse homolog of human SPINK1) has dual functions for trypsin inhibition: one as a trypsin inhibitor by direct binding to trypsin 24 and another as a suppressor of autophagy, which is involved in trypsinogen activation. 25,26 In summary, mutations in PRSS1 27 and SPINK1 19 genes are acknowledged as genetic risk factors for pancreatitis in human patients.…”