Supervillin reorganizes the actin cytoskeleton and increases invadopodial efficiency

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Invadopodia and podosomes are actin-rich cell structures crucial for extracellular matrix (ECM) degradation and tissue invasion by tumor cells.
• Supervillin (SV) is a peripheral membrane protein known to interact with F-actin and myosin II, suggesting a role in cytoskeletal organization.

Purpose of the Study:

• To investigate the role of supervillin (SV) in the function of invadopodia and podosomes.
• To determine if SV influences actin cytoskeleton organization and ECM degradation by tumor cells.

Main Methods:

• Overexpression of enhanced green fluorescent protein (EGFP)-tagged SV in cultured cells.
• RNA interference (RNAi)-mediated knockdown of SV.
• Confocal microscopy to visualize F-actin, SV, and associated proteins (cortactin, Tks5, cdc42).
• ECM degradation assays using fluorescently labeled substrates.
• Cell invasion assays through ECM.

Main Results:

• Overexpressed SV induced the formation of dynamic F-actin punctae colocalizing with podosome/invadopodial proteins, including cortactin.
• SV directly binds cortactin in vitro, and cortactin is necessary for SV-induced punctae formation.
• SV localized to the core of podosomes and invadopodia in different cell types.
• EGFP-SV overexpression increased ECM degradation, while SV knockdown decreased it.
• Simultaneous knockdown of SV and gelsolin reduced ECM invasion.

Conclusions:

• Supervillin (SV) is a component of podosomes and invadopodia.
• SV potentiates invadopodial function, likely by mediating cortactin localization and/or dynamics of matrix-degrading enzymes.
• SV plays a significant role in tumor cell invasion through ECM degradation.