Granzyme B-induced and caspase 3-dependent cleavage of gelsolin by mouse cytotoxic T cells modifies cytoskeleton dynamics

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Granule-associated perforin and granzymes (gzms) are crucial effector molecules for cytotoxic T lymphocytes (Tc cells) and natural killer cells.
• While gzms are traditionally viewed for their cytotoxic activity, emerging evidence suggests diverse non-cytotoxic functions, including pro-inflammatory cytokine stimulation and anti-viral roles.

Purpose of the Study:

• To investigate the non-cytotoxic functions of granzyme B (gzmB) in target cell manipulation.
• To elucidate the mechanism by which gzmB affects the actin cytoskeleton within target cells.

Main Methods:

• In vitro cleavage assays using isolated mouse gzmB and mouse cytoplasmic gelsolin (c-gelsolin).
• Delivery of gzmB to intact target cells via ex vivo immune Tc cells.
• Analysis of caspase activation and actin cytoskeleton integrity following gzmB delivery.

Main Results:

• Isolated mouse gzmB cleaves mouse c-gelsolin in vitro.
• When delivered by Tc cells, gzmB induces c-gelsolin proteolysis through caspase 3/7 activation.
• The N-terminal c-gelsolin fragment severs actin filaments without causing cell death, disrupting the actin cytoskeleton.

Conclusions:

• GzmB secreted by Tc cells initiates a caspase cascade that disintegrates the target cell's actin cytoskeleton.
• This intracellular actin cytoskeleton remodeling by gzmB may represent a novel mechanism for anti-viral host defense.