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Related Concept Videos

Caspases01:24

Caspases

Caspase, a family of cysteine proteases, serve as effectors in apoptosis. The ced3 gene in C.elegans was first identified to be involved in apoptosis. This gene encodes the ced-3 caspase that is similar to the interleukin-1-beta converting enzyme or ICE in mammals. In addition to apoptosis, caspases also function in the inflammatory response. Inflammatory caspases are essential in activating pro-inflammatory cytokines that recruit immune cells and block the replication of pathogens inside cells.
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Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of polypeptide chains. After polypeptide chains are broken into individual amino acids by a series of digestive enzymes, the amino acids are transported to the liver via the bloodstream to produce energy.
Tight Junctions01:29

Tight Junctions

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Protein Absorption01:12

Protein Absorption

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Pathophysiology of Peptic Ulcer Disease: Injurious Factors01:22

Pathophysiology of Peptic Ulcer Disease: Injurious Factors

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Acute Pancreatitis II: Pathophysiology

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Related Experiment Video

Updated: Jun 23, 2026

Demonstration of Proteolytic Activation of the Epithelial Sodium Channel (ENaC) by Combining Current Measurements with Detection of Cleavage Fragments
08:56

Demonstration of Proteolytic Activation of the Epithelial Sodium Channel (ENaC) by Combining Current Measurements with Detection of Cleavage Fragments

Published on: July 5, 2014

Serine proteases decrease intestinal epithelial ion permeability by activation of protein kinase Czeta.

Veronica A Swystun1, Bernard Renaux, France Moreau

  • 1Inflammation Research Network, Department of Physiology and Pharmacology, University of Calgary, Calgary T2N 4N1, Canada.

American Journal of Physiology. Gastrointestinal and Liver Physiology
|May 23, 2009
PubMed
Summary
This summary is machine-generated.

Digestive serine proteases enhance intestinal epithelial barrier function by increasing tight junction protein occludin. This process, independent of protease-activated receptors, involves protein kinase C zeta (PKCzeta) activation.

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Area of Science:

  • Gastroenterology
  • Cell Biology
  • Epithelial Physiology

Background:

  • Epithelial permeability is crucial for gut fluid balance, and its disruption leads to intestinal diseases.
  • Digestive serine proteases are key enzymes in nutrient breakdown within the gut.

Purpose of the Study:

  • To investigate the impact of digestive serine proteases on intestinal epithelial paracellular permeability.
  • To elucidate the molecular mechanisms underlying protease-mediated changes in epithelial barrier function.

Main Methods:

  • Utilized polarized intestinal epithelial cell monolayers to assess transepithelial resistance (R(TE)) and ion/dextran permeability.
  • Employed enzyme activity assays, protease-activated receptor (PAR) activators, and isoform-specific inhibitors (PKCzeta inhibitor, Ca2+ chelators).
  • Analyzed occludin and zonula occludin-1 (ZO-1) localization and interaction via immunostaining and co-immunoprecipitation.

Main Results:

  • Trypsin, chymotrypsin, and elastase increased R(TE), decreasing paracellular conductances and permeability to large molecules.
  • Protease effects were enzyme-dependent but independent of known PARs.
  • PKCzeta activation was critical, as its inhibition blocked protease-induced R(TE) increases.
  • Protease treatment enhanced occludin-ZO-1 complex formation in the cell junctional complex, an effect dependent on PKCzeta.

Conclusions:

  • Digestive serine proteases enhance intestinal epithelial barrier function.
  • This enhancement is mediated by PKCzeta activation, independent of PARs.
  • Increased occludin localization to tight junctions contributes to improved epithelial barrier integrity.