Structural and biological consequences of increased vimentin expression in simple epithelial cell types

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Cytoskeletal intermediate filaments (IFs) are diverse proteins with tissue-specific expression patterns.
• Vimentin IFs are typically found in mesenchymal cells but can be expressed in other cell types during various biological processes.
• Understanding vimentin's role in non-mesenchymal cells is crucial for comprehending cellular differentiation and disease.

Purpose of the Study:

• To investigate the impact of elevated vimentin expression on the phenotype of simple epithelial cells.
• To model early extraembryonic epithelial differentiation using HR9 and F9 cell lines.

Main Methods:

• Transfection of murine HR9 endoderm and F9 embryonal carcinoma cell lines with a human vimentin cDNA expression vector.
• Characterization of stable clones expressing varying levels of human vimentin using immunofluorescence and biochemical analysis.

Main Results:

• High vimentin levels in epithelial cells led to aberrant vimentin structures and co-collapse of keratin K8/K18 filaments.
• Reduced keratin protein levels and mislocalization of desmosomal proteins (DP I/II) were observed in F9 cells.
• Excess intracellular vimentin caused nuclear distortion, slowed cell proliferation, and delayed cell spreading, with a threshold effect noted.

Conclusions:

• Wild-type vimentin can induce significant phenotypic changes in epithelial cells when present at high intracellular concentrations, acting akin to a mutant protein.
• These findings highlight the importance of balanced intermediate filament expression for maintaining normal cellular structure and function.