SerpinI2 (pancpin) is an inhibitory serpin targeting pancreatic elastase and chymotrypsin

Biochim Biophys Acta Proteins Proteom. 2017 Feb;1865(2):195-200. doi: 10.1016/j.bbapap.2016.10.013. Epub 2016 Oct 27.

Abstract

SerpinI2/Pancpin/MEPI is a 46kDa member of the serpin (serine protease inhibitor) superfamily. It is downregulated in pancreatic and breast cancer, and associated with acinar cell apoptosis and pancreatic insufficiency when absent in mice. However, the target protease and protein properties of serpinI2 are previously uncharacterised. We have expressed and purified recombinant serpin I2 in E. coli. The protein exhibited thermal instability typical of inhibitory serpins, which was lost following RCL cleavage. SerpinI2 did not inhibit trypsin, but was found to inhibit pancreatic chymotrypsin and elastase with Kass values >105M-1s-1, and with stoichiometry of inhibition of 1.4 and 1.7 respectively. Mutagenesis of the predicted critical hinge region residue Ser344 abolished inhibitory activity, and a cleavage site C-terminal to Met358 was identified. The protein is also prone to polymerisation/aggregation at 45°C, a characteristic of serpins associated with disease. This study therefore reveals a function for serpinI2 and supports the hypothesis that this protein can protect pancreatic cells from prematurely activated zymogens.

Keywords: Chymotrypsin; Elastase; Pancpin; Pancreatic insufficiency; Serpin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cell Line
  • Chymotrypsin / antagonists & inhibitors*
  • Escherichia coli / metabolism
  • Neoplasm Proteins / pharmacology
  • Pancreatic Elastase / antagonists & inhibitors*
  • Recombinant Proteins / pharmacology
  • Sequence Homology, Amino Acid
  • Serine Proteinase Inhibitors / pharmacology*
  • Serpins / pharmacology*
  • Somatostatin-Secreting Cells / drug effects
  • Somatostatin-Secreting Cells / metabolism
  • Substrate Specificity
  • Trypsin / metabolism

Substances

  • Neoplasm Proteins
  • Recombinant Proteins
  • Serine Proteinase Inhibitors
  • Serpins
  • Chymotrypsin
  • Pancreatic Elastase
  • Trypsin