Relationship between cell surface protease activity and doubling time in various normal and transformed cells

Area of Science:

• Biochemistry
• Cell Biology
• Enzymology

Background:

• Cell surface proteases play roles in various biological processes.
• Quantifying cell surface protease activity is crucial for understanding cell behavior.

Purpose of the Study:

• To develop a sensitive method for measuring cell surface and secreted protease activity.
• To investigate the characteristics and regulation of cell surface proteases.

Main Methods:

• A radioassay using 3H-labelled casein as a substrate was developed.
• Proteolytic degradation products were measured as trichloracetic acid soluble peptides.
• Cell lines were cultured, synchronized, and their surface protease activity quantified.

Main Results:

• All cultured cell lines exhibited cell surface protease activity not secreted into the media.
• Transformed mouse epidermal cells showed significantly higher protease activity than normal cells.
• Surface protease activity increased during mitosis and correlated inversely with cell doubling times.

Conclusions:

• Cell surface proteases, distinct from plasminogen activator or plasmin, are present in cultured cells.
• Elevated surface protease activity in transformed cells and during mitosis suggests a role in cell proliferation.
• Cell surface proteases may be key regulators of cell growth rates in culture.