Ethanol Enhances TGF-β Activity by Recruiting TGF-β Receptors From Intracellular Vesicles/Lipid Rafts/Caveolae to...

Area of Science:

• Cellular biology
• Molecular signaling
• Biochemistry

Background:

• Ethanol consumption has dual effects on health, benefiting atherosclerotic cardiovascular disease (ASCVD) but causing alcoholic liver disease (ALD).
• The underlying molecular mechanisms for ethanol's beneficial and detrimental effects remain unclear.
• Transforming growth factor-beta (TGF-β) signaling is implicated in both ASCVD and ALD.

Purpose of the Study:

• To investigate how ethanol influences canonical TGF-β signaling pathways.
• To elucidate the role of ethanol in the cellular localization of TGF-β receptors.
• To understand the molecular basis for ethanol's opposing effects on ASCVD and ALD.

Main Methods:

• Utilized Mv1Lu cells with a luciferase reporter gene dependent on Smad2.
• Measured TGF-β-stimulated luciferase activity and P-Smad2 levels in response to ethanol.
• Assessed cell-surface TGF-β receptor expression and localization using I(125)-TGF-β cross-linking, Western blot, sucrose density gradient ultracentrifugation, and immunofluorescence staining.

Main Results:

• Ethanol (0.5-1%) enhanced TGF-β-stimulated luciferase activity.
• Low ethanol concentrations (0.5%) increased P-Smad2 levels and cell-surface TβR-II expression.
• Ethanol displaced TGF-β receptors (TβR-I and TβR-II) from lipid rafts, promoting their translocation to non-raft signaling domains.

Conclusions:

• Ethanol enhances canonical TGF-β signaling by altering the localization of TGF-β receptors.
• This mechanism may explain ethanol's beneficial effects on ASCVD and harmful effects on ALD.
• Ethanol's disruption of lipid raft-dependent signaling platforms may contribute to pathologies in various tissues.