Improved methods for separation of human cytokeratins

Area of Science:

• Biochemistry
• Cell Biology
• Proteomics

Background:

• Cytokeratins are intermediate filament proteins crucial for epithelial cell structure and function.
• Human bladder and esophageal epithelia express specific cytokeratin profiles relevant to tissue differentiation and disease.

Purpose of the Study:

• To isolate and characterize acidic cytokeratins from human bladder and esophageal epithelia.
• To investigate the heterogeneity of these cytokeratins based on their hydrophobic properties.

Main Methods:

• Extraction of cytokeratins from autopsy tissue using differential salt buffers.
• Solubilization of cytokeratin pellets using urea and imidazole.
• Separation and fractionation using DEAE ion exchange chromatography and reverse-phase High-Performance Liquid Chromatography (HPLC).
• Analysis of fractions using one- and two-dimensional electrophoresis and Western blotting.

Main Results:

• Urea and imidazole facilitated cytokeratin solubilization, while reducing agents were ineffective.
• DEAE chromatography yielded three fractions, with the third containing acidic cytokeratins.
• Reverse-phase HPLC of acidic cytokeratins from esophagus produced seven distinct peaks.
• Western blotting confirmed that all seven HPLC peaks contained an epitope specific to cytokeratin 13.
• Significant variations in hydrophobic characteristics were observed among the isolated peptide products.

Conclusions:

• The developed chromatographic methods effectively isolated and separated acidic cytokeratins from human epithelial tissues.
• The isolated peptides, while sharing a common cytokeratin 13 epitope, display a range of hydrophobic properties.
• This suggests post-translational modifications or degradation leading to peptides with altered hydrophobicity but conserved antigenic sites.