Hereditary pancreatitis caused by mutation-induced misfolding of human cationic trypsinogen: A novel disease mechanism

Abstract

We investigated the biochemical properties and cellular expression of the c.346C>T (p.R116C) human cationic trypsinogen (PRSS1) mutant, which we identified in a German family with autosomal dominant hereditary pancreatitis. This mutation leads to an unpaired Cys residue with the potential to interfere with protein folding via incorrect disulfide bond formation. Recombinantly expressed p.R116C trypsinogen exhibited a tendency for misfolding in vitro. Biochemical analysis of the correctly folded, purified p.R116C mutant revealed unchanged activation and degradation characteristics compared to wild type trypsinogen. Secretion of mutant p.R116C from transfected 293T cells was reduced to ~20% of wild type. A similar secretion defect was observed with another rare PRSS1 variant, p.C139S, whereas mutants p.A16V, p.N29I, p.N29T, p.E79K, p.R122C, and p.R122H were secreted normally. All mutants were detected in cell extracts at comparable levels but a large portion of mutant p.R116C was present in an insoluble, protease-sensitive form. Consistent with intracellular retention of misfolded trypsinogen, the endoplasmic reticulum (ER) stress markers BiP and XBP1s were elevated in cells expressing mutant p.R116C. The results indicate that mutation induced misfolding and intracellular retention of human cationic trypsinogen causes hereditary pancreatitis in carriers of the p.R116C mutation. ER stress triggered by trypsinogen misfolding represents a new potential disease mechanism for chronic pancreatitis.

Genetics of Pancreatitis: The 2014 Update

“…CPA1 had no detectable effect on trypsinogen activation, trypsin activity or trypsinogen degradation by CTRC, indicating that CPA1 variants do not exert their effect via increasing the intrapancreatic trypsin activity. On the other hand, most of the loss-of-function CPA1 variants exhibit markedly reduced secretion, raising the possibility that CPA1 variants undergo misfolding in the ER and cause ER stress, as demonstrated previously for some PRSS1 and CTRC mutants (Kereszturi et al 2009b;Beer et al 2013). Indeed, the expression of p.N256K variant in AR42J rat pancreatic acinar cells resulted in ER stress, as evidenced by increased splicing of X-box binding protein 1 and elevated mRNA levels of the chaperons BiP and calreticulin.…”

Tauroursodeoxycholic acid reduces endoplasmic reticulum stress, trypsin activation, and acinar cell apoptosis while increasing secretion in rat pancreatic acini

“…It may further explain successful treatments of idiopathic and autoimmune pancreatitis by bile salts demonstrated in several case reports and small pilot studies in humans (38,46,49). Thus this treatment strategy may become important, even though a recent publication showed a connection between ER stress and hereditary pancreatitis (19).…”

Loss of acinar cell IKKα triggers spontaneous pancreatitis in mice

“…A pathogenic role for ER stress is supported by a mutation (p.R116C) that causes misfolding and intracellular retention of human PRSS1, but does not affect its activation (6). This mutation, which causes ER stress, results in chronic pancreatitis.…”