Significance of trypsin inhibitor gene mutation in the predisposition to pancreatitis

Abstract

Pancreatic secretory trypsin inhibitor (PSTI) is a potent natural inhibitor of trypsin. We proposed a hypothesis: if the function of PSTI is impaired by its genetic mutation, trypsin may easily promote autodigestion causing pancreatitis, and performed mutational analysis of PSTI gene in patients with pancreatitis. Two exonic mutations (N34S and R67C) were suggested to be associated with the predisposition to pancreatitis. N34S mutation was co-segregated with two intronic mutations, IVS1-37T>C and IVS3-69insTTTT. Although we analyzed the function of recombinant N34S protein, we could not demonstrate the loss of function of this protein. Intronic mutations rather than N34S itself (IVS1-37T>C+N34S+IVS3-69insTTTT complex) may be associated with the decreased function of PSTI. Alternatively, increased digestion of N34S in vivo may be applicable. As for R67C, the conformational alteration of the protein by forming intramolecular or intermolecular disulfide bonds with 67Cys was strongly suggested. These results, along with the brand new findings in PSTI knockout mice, suggest that genetic mutation of PSTI is one of the important mechanisms for predisposition to pancreatitis by lowering the trypsin inhibitory function.