Polyamines regulate Rho-kinase and myosin phosphorylation during intestinal epithelial restitution

Area of Science:

• Cell Biology
• Gastroenterology
• Molecular Biology

Background:

• Polyamines are vital for early mucosal restitution, involving epithelial cell migration.
• Previous work linked polyamines to increased RhoA activity via calcium (Ca2+) and membrane potential (Em).
• The role of Rho-kinase (ROK/ROCK) in this polyamine-mediated process remained unclear.

Purpose of the Study:

• To investigate if elevated cytosolic free Ca2+ ([Ca2+]cyt) and subsequent RhoA activation trigger Rho-kinase (ROK/ROCK) signaling.
• To determine if ROK/ROCK activation leads to myosin light chain (MLC) phosphorylation during intestinal epithelial restitution.
• To elucidate the role of the RhoA-ROCK-MLC pathway in polyamine-enhanced cell migration.

Main Methods:

• Experiments utilized differentiated intestinal epithelial cells (IEC-Cdx2L1).
• Manipulated [Ca2+]cyt levels through polyamine depletion, Ca2+-free medium, or ionomycin.
• Assessed RhoA, ROCK-1, ROKalpha protein levels, Rho-kinase activity, MLC phosphorylation, and cell migration.

Main Results:

• Reduced [Ca2+]cyt decreased RhoA, ROCK-1, ROKalpha, Rho-kinase activity, and MLC phosphorylation, inhibiting cell migration.
• Elevated [Ca2+]cyt increased GTP-bound RhoA, ROCK proteins, Rho-kinase activity, and MLC phosphorylation.
• Inhibiting RhoA or ROK/ROCK suppressed Rho-kinase activity, MLC phosphorylation, and cell migration.

Conclusions:

• Polyamines elevate [Ca2+]cyt, activating RhoA, which in turn activates Rho-kinase (ROK/ROCK) during intestinal epithelial restitution.
• Activated Rho-kinase phosphorylates MLC, promoting myosin stress fiber formation and enhancing cell migration.
• The polyamine-induced RhoA-ROCK-MLC pathway is critical for effective intestinal mucosal repair.