MT1-MMP recognition by ERM proteins and its implication in CD44 shedding

Area of Science:

• Molecular Cell Biology
• Biochemistry
• Cancer Research

Background:

• Membrane type 1-matrix metalloproteinase (MT1-MMP) facilitates tumor invasion by shedding CD44.
• Ezrin/radixin/moesin (ERM) proteins link cell surface proteins to the actin cytoskeleton.
• CD44 shedding is crucial for tumor cell motility and invasion.

Purpose of the Study:

• To elucidate the molecular mechanism by which MT1-MMP interacts with ERM proteins and CD44.
• To investigate the role of radixin in recruiting MT1-MMP to CD44 for F-actin anchoring.
• To understand how ERM proteins mediate the interaction between MT1-MMP and its substrate CD44.

Main Methods:

• Co-immunoprecipitation assays to demonstrate protein interactions.
• Crystal structure analysis of the MT1-MMP cytoplasmic tail bound to radixin's FERM domain.
• Biochemical assays to confirm simultaneous binding of radixin to both MT1-MMP and CD44.

Main Results:

• The cytoplasmic tail of MT1-MMP directly binds to the FERM domain of radixin.
• Crystal structure reveals a unique binding interface between MT1-MMP and radixin subdomain A.
• Radixin simultaneously binds MT1-MMP and CD44, mediating their colocalization and F-actin anchoring.

Conclusions:

• ERM proteins, specifically radixin, act as crucial adaptors, linking MT1-MMP to CD44 and the F-actin cytoskeleton.
• This ERM protein-mediated interaction facilitates MT1-MMP recruitment to CD44, accelerating substrate shedding.
• The findings reveal a novel mechanism contributing to MT1-MMP-driven tumor cell invasion.