A novel role for FAK as a protease-targeting adaptor protein: regulation by p42 ERK and Src

Area of Science:

• Cell biology
• Molecular biology
• Biochemistry

Background:

• Cell migration relies on the dynamic turnover of integrin-dependent adhesions.
• Nonreceptor tyrosine kinases like Src and FAK, and ERK/MAP kinase-activated Calpain 2, are implicated in focal-adhesion turnover.
• The precise interplay between FAK, Src, and Calpain 2 in this process remains unclear.

Purpose of the Study:

• To elucidate the role of FAK in focal-adhesion turnover and cell migration.
• To investigate the potential link between FAK, Calpain 2, and ERK/MAP kinase signaling in focal adhesion dynamics.
• To identify novel functions of FAK beyond its kinase activity.

Main Methods:

• Utilized cell migration assays and biochemical analyses.
• Employed site-directed mutagenesis to disrupt FAK-Calpain 2 interaction.
• Investigated protein complex formation and localization using cell-based assays.
• Assessed the impact of FAK mutations on Calpain 2/p42ERK complex assembly and MEK/ERK activity.

Main Results:

• Identified a novel, kinase-independent function of FAK as an adaptor molecule.
• Demonstrated that FAK mediates the assembly of a complex involving Calpain 2 and p42ERK.
• Showed that mutations in FAK's proline-rich region disrupt Calpain 2 binding and complex formation.
• Linked complex formation and MEK/ERK activity to FAK proteolysis, focal adhesion turnover, and cell migration.
• Confirmed FAK's necessity in recruiting Calpain 2 and p42ERK to adhesion sites.

Conclusions:

• FAK functions as a crucial adaptor, integrating Calpain 2 and ERK/MAPK signaling for focal adhesion turnover.
• This FAK-mediated complex formation is essential for regulating cell migration.
• FAK's role extends beyond kinase activity, highlighting its importance as a scaffold in cell adhesion dynamics.