Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 277, Issue 24, Pages 21389-21396Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M200878200
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- NIDDK NIH HHS [DK58088] Funding Source: Medline
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The lysosomal cysteine protease cathepsin B is thought to play a central role in intrapancreatic trypsinogen activation and the onset of experimental pancreatitis. Recent in vitro studies have suggested that this mechanism might be of pathophysiological relevance in hereditary pancreatitis, a human inborn disorder associated with mutations in the cationic trypsinogen gene. In the present study evidence is presented that cathepsin B is abundantly present in the secretory compartment of the human exocrine pancreas, as judged by immunogold electron microscopy. Moreover, pro-cathepsin B and mature cathepsin B are both secreted together with trypsinogen and active trypsin into the pancreatic juice of patients with sporadic pancreatitis or hereditary pancreatitis. Finally, cathepsin B-catalyzed activation of recombinant human cationic trypsinogen with hereditary pancreatitis-associated mutations N291, N29T, or R122H were characterized. In contrast to a previous report, cathepsin B-mediated activation of wild type and all three mutant trypsinogen forms was essentially identical under a wide range of experimental conditions. These observations confirm the presence of active cathepsin B in the human pancreatic secretory pathway and are consistent with the notion that cathepsin B-mediated trypsinogen activation might play a pathogenic role in human pancreatitis. On the other hand, the results clearly demonstrate that hereditary pancreatitis-associated mutations do not lead to increased or decreased trypsinogen activation by cathepsin B. Therefore, mutation-dependent alterations in cathepsin B-induced trypsinogen activation are not the cause of hereditary pancreatitis.
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