Ouabain increases gap junctional communication in epithelial cells.

Area of Science:

• Cell Biology
• Physiology
• Molecular Biology

Background:

• Endogenous ouabain functions as a hormone.
• Previous studies demonstrated ouabain's role in modulating cell-cell contacts like tight junctions and polarity.
• The current study investigates ouabain's impact on gap junction communication (GJC).

Purpose of the Study:

• To determine if physiological concentrations of ouabain affect gap junction communication (GJC).
• To elucidate the molecular mechanisms underlying ouabain's effect on GJC.

Main Methods:

• Neurobiotin diffusion assay in MDCK cells to quantify GJC.
• Electrical capacitance measurements.
• Inhibition assays using protein kinase inhibitors (c-Src, ERK1/2) and protein synthesis inhibitors (cycloheximide, actinomycin D).
• Gene silencing assays targeting connexins.

Main Results:

• 10 nM ouabain increased GJC by 475% within 1 hour in MDCK cells.
• The Na+-K+-ATPase serves as the ouabain receptor.
• Inhibition of c-Src and ERK1/2 blocked the ouabain-induced GJC enhancement.
• The effect was independent of new protein synthesis.
• Ouabain-induced GJC enhancement involves connexins 32 and 43.

Conclusions:

• Physiological ouabain (10 nM) significantly increases GJC in MDCK cells.
• The mechanism involves Na+-K+-ATPase, c-Src, ERK1/2, and connexins 32/43.
• Ouabain enhances GJC without requiring de novo protein synthesis.