Possible involvement of caspase-like family in maintenance of cytoskeleton integrity

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Caspases are key cysteine proteases regulating apoptosis.
• They are known to cleave cellular proteins and activate cytokines.
• Their role beyond apoptosis is less understood.

Purpose of the Study:

• To investigate a novel function of caspases in cell adhesion and spreading.
• To identify the specific caspases involved in regulating cell spreading.
• To elucidate the molecular mechanisms underlying caspase-mediated cell spreading.

Main Methods:

• Dose-dependent inhibition of cell spreading using Z-Asp-CH2-DCB (Z-Asp), a general caspase inhibitor.
• Assay of caspase 3-like and caspase 1-like activity in adherent and suspended cells.
• Testing specific caspase inhibitors (Z-DEVD, Z-YVAD) and activators (PMA, LPA, bradykinin, sphingosine-1-phosphate).
• Immunoprecipitation to assess focal adhesion kinase (FAK) protein expression.

Main Results:

• Z-Asp inhibited cell spreading on collagen-coated plates without affecting cell viability.
• Caspase 3-like activity was detected in adherent cells, inhibited by Z-Asp.
• Only Z-Asp, not specific inhibitors, suppressed cell spreading.
• Z-Asp's inhibitory effect was counteracted by PMA and LPA, suggesting Rho signaling involvement.
• Z-Asp downregulated FAK protein expression in adherent cells.

Conclusions:

• A novel role for caspases in maintaining cytoskeleton integrity via FAK protein expression is suggested.
• The study implies that unknown caspases, not caspase 1 or 3, are crucial for cell spreading.
• This finding expands the known functions of caspases beyond apoptosis.