Ethanol selectively impairs clathrin-mediated internalization in polarized hepatic cells

Area of Science:

• Hepatology
• Cell Biology
• Molecular Toxicology

Background:

• Alcoholic liver disease (ALD) is a significant health concern, yet its molecular underpinnings remain unclear.
• Previous studies suggested ethanol selectively impairs clathrin-mediated endocytosis in liver cells (WIF-B).
• Understanding ethanol's effect on cellular transport is crucial for ALD pathogenesis.

Purpose of the Study:

• To investigate the selective impact of ethanol on various endocytic pathways in liver cells.
• To elucidate the molecular mechanisms by which ethanol induces hepatotoxicity via endocytosis disruption.
• To determine if ethanol affects the internalization of proteins lacking known internalization signals.

Main Methods:

• Utilized WIF-B cells treated with ethanol.
• Assessed the internalization of various marker proteins and compounds via clathrin-mediated, caveolae/raft-mediated, and fluid phase endocytosis.
• Examined the localization of clathrin heavy chain and dynamin-2.
• Investigated the effect of dominant-negative dynamin-2 on protein internalization.

Main Results:

• Ethanol selectively impaired the internalization of markers utilizing clathrin-mediated endocytosis.
• Internalization via caveolae/raft-mediated, fluid phase, or non-vesicular pathways remained unaffected.
• Ethanol caused clathrin heavy chain accumulation and reduced dynamin-2 membrane association.
• Internalization of apical proteins lacking known signals was also disrupted, suggesting clathrin-mediated uptake.

Conclusions:

• Ethanol selectively disrupts hepatic clathrin-mediated endocytosis.
• The primary mechanism involves the prevention of vesicle fission from the plasma membrane.
• This impairment of clathrin-mediated internalization contributes to alcohol-induced hepatotoxicity.