Paxillin phosphorylation controls invadopodia/podosomes spatiotemporal organization

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Invadopodia are dynamic actin-rich structures involved in cell invasion and matrix degradation.
• In Rous sarcoma virus (RSV)-transformed baby hamster kidney (BHK) cells, invadopodia self-organize into rings and belts.
• This organization resembles podosome distribution during osteoclast differentiation.

Purpose of the Study:

• To investigate the regulatory mechanisms controlling invadopodia ring formation and disassembly.
• To elucidate the role of paxillin phosphorylation in invadopodia dynamics.
• To understand the functional significance of invadopodia ring expansion in extracellular matrix degradation and cell migration.

Main Methods:

• Utilized Rous sarcoma virus (RSV)-transformed baby hamster kidney (BHK) cells and primary osteoclasts.
• Employed ectopic expression of paxillin mutants (Y31F-Y118F).
• Performed paxillin knockdown, calpain inhibition, and extracellular signal-regulated kinase (Erk) inhibition.

Main Results:

• Invadopodia ring expansion is controlled by paxillin phosphorylations at tyrosine 31 and 118, which facilitate invadopodia disassembly.
• Ectopic expression of a non-phosphorylatable paxillin mutant (Y31F-Y118F) delayed invadopodia disassembly and impaired self-organization.
• Paxillin phosphorylation promotes Erk activation, which in turn activates calpain, suggesting these proteins are in the same regulatory pathway.
• Invadopodia/podosome ring expansion is essential for efficient extracellular matrix degradation and cell transmigration.

Conclusions:

• Paxillin phosphorylation is a key regulator of invadopodia disassembly and self-organization.
• The paxillin-Erk-calpain pathway governs invadopodia dynamics.
• Invadopodia ring expansion is crucial for extracellular matrix degradation and cell migration in both transformed cells and osteoclasts.