Variants in CPA1 are strongly associated with early onset chronic pancreatitis

Abstract

Chronic pancreatitis is an inflammatory disorder of the pancreas. We analyzed CPA1 encoding carboxypeptidase A1 in subjects with non-alcoholic chronic pancreatitis and controls in a German discovery cohort and three replication cohorts. Functionally impaired variants were present in 29/944 (3.1%) German patients and in 5/3,938 (0.1%) controls (odds ratio [OR] = 24.9; P = 1.5 × 10-16). The association was strongest in subjects aged ≤10 years (9.7%; OR = 84.0; P = 4.1 × 10-24). In the replication cohorts, defective CPA1 variants were observed in 8/600 (1.3%) patients and in 9/2,432 (0.4%) controls from Europe (P = 0.01), in 5/230 (2.2%) patients and 0/264 controls from India (P = 0.02), and in 5/247 (2.0%) patients but 0/341 controls from Japan (P = 0.013). The mechanism of increased pancreatitis risk by CPA1 variants may involve misfolding-induced endoplasmic reticulum stress rather than elevated trypsin activity as seen with other genetic risk factors.

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]. The majority of impaired CPA1 variants exhibited a secretion defect due to intracellular misfolding and retention.…”

Complex Formation of Human Proelastases with Procarboxypeptidases A1 and A2

“…The physiological significance of complex formation has never been solved, although coordination of zymogen activation seemed a plausible possibility (14 -17). Our interest turned to these older studies when we identified that loss-of-function CPA1 mutations increased risk for chronic pancreatitis in children and we were searching for possible mechanisms to explain pathogenesis (6). We realized that complex formation among pancreatic protease zymogens has never been studied using post-genomic era tools.…”

“…Plasmid Construction and Mutagenesis-Construction of expression plasmids for human CELA3A, CELA3B, CTRC, CTRB1, CTRB2, CTRL1, CPA1, CPA2, and CPB1 in the pcDNA3.1(Ϫ) vector was described previously (2,6,8,9,49,50). C-terminal His 10 tags were engineered to the proelastase and chymotrypsinogen expression plasmids using gene synthesis (GenScript, Piscataway, NJ).…”

“…Full activation of human procarboxypeptidases A1 (proCPA1) 2 and A2 (proCPA2) requires additional cleavages by chymotrypsin C (CTRC) to facilitate dissociation of the inhibitory activation peptide (2). Renewed interest in digestive protease physiology was spurred by the recognition that mutations in cationic trypsinogen (PRSS1), the pancreatic secretory trypsin inhibitor (SPINK1), CTRC and CPA1 are strongly associated with chronic pancreatitis in humans (3)(4)(5)(6). At the same time, information obtained from genome and pancreatic transcriptome sequencing allowed correct annotation of the full complement of digestive protease isoforms and opened up avenues for investigations using genetically-defined recombinant enzymes.…”

“…At the same time, information obtained from genome and pancreatic transcriptome sequencing allowed correct annotation of the full complement of digestive protease isoforms and opened up avenues for investigations using genetically-defined recombinant enzymes. These studies, in turn, led to novel insight into digestive protease function such as the central role of CTRC in the regulation of human trypsinogen (7-9) and procarboxypeptidase activation (2), the role of mesotrypsin (PRSS3) in degrading trypsin inhibitors (10, 11), and the significance of mutation-induced digestive protease misfolding in acinar cell stress and chronic pancreatitis (6,12,13).A long known yet still unsolved enigma in digestive protease biochemistry is the physiological function of complex formation. Although most zymogens are secreted in their monomeric forms, ternary and binary complexes have also been identified (for reviews, see Refs.…”