Raptor knockdown concurrently increases the electrical resistance and paracellular permeability of Caco-2 cell...

Area of Science:

• Cell biology
• Gastroenterology
• Molecular signaling

Background:

• The mechanistic target of rapamycin complex 1 (mTORC1) is a key regulator of nutrient sensing, growth, metabolism, and intestinal homeostasis.
• Intestinal barrier integrity is crucial for maintaining tissue homeostasis by controlling epithelial permeability.
• The precise role of mTORC1 in regulating intestinal barrier function and permeability requires further investigation.

Purpose of the Study:

• To investigate the effects of modulating mTORC1 signaling on intestinal barrier function and permeability.
• To elucidate the mechanisms by which mTORC1 influences epithelial barrier integrity.

Main Methods:

• Utilized lentivirus-mediated knockdown of mTORC1 signaling proteins Raptor and TSC2 in Caco-2 cell monolayers.
• Assessed changes in transepithelial electrical resistance (TEER) and dextran permeability.
• Analyzed tight junction protein expression, autophagy levels, and myosin light chain phosphorylation.

Main Results:

• Raptor knockdown increased TEER and paracellular permeability, leading to a leaky monolayer for dextran but retained ion resistance.
• Paracellular permeability was associated with reduced tight junction proteins and increased autophagy.
• Raptor depletion increased MYPT1 and decreased p-MYPT1 and p-MLC, indicating increased myosin light chain phosphatase activity and relaxation.

Conclusions:

• Epithelial paracellular permeability to small molecules like dextran is distinct from transepithelial electrical resistance.
• mTORC1 signaling, particularly via Raptor, plays a complex role in regulating intestinal barrier integrity and permeability.