The complex of Fas-associated factor 1 with Hsp70 stabilizes the adherens junction integrity by suppressing RhoA...

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Fas-associated factor 1 (FAF1) is a scaffolding protein implicated in various diseases, including cancers.
• FAF1 possesses multiple ubiquitin-related domains that mediate interactions with specific partners.
• The interaction between FAF1's UBL1 domain and heat shock protein 70 (Hsp70) is linked to tumor formation, but its mechanism is unclear.

Purpose of the Study:

• To elucidate the molecular mechanism underlying the interaction between FAF1 and Hsp70.
• To investigate the role of the FAF1-Hsp70 complex in regulating cell-cell junctions and RhoA activation.
• To determine the implications of FAF1 function in cancer progression and metastasis.

Main Methods:

• Structural analysis to identify key residues involved in FAF1-Hsp70 interaction.
• Biochemical assays to assess the formation and function of the FAF1-Hsp70-IQGAP1 complex.
• 3D spheroid cell culture models to evaluate the impact of FAF1 depletion on cell invasion.

Main Results:

• Structural analysis identified Histidine 160 (His160) of FAF1 as crucial for Hsp70 binding.
• The FAF1-Hsp70 complex formation is essential for subsequent interaction with IQGAP1.
• FAF1, through the FAF1-Hsp70-IQGAP1 complex, negatively regulates RhoA activation, thereby stabilizing cell-to-cell junctions.
• FAF1 depletion enhanced collective invasion in 3D spheroid models, indicating a role in suppressing metastasis.

Conclusions:

• FAF1 is a critical regulator of adherens junction integrity during tissue homeostasis and morphogenesis.
• The FAF1-Hsp70 complex acts as a novel suppressor of RhoA activation, preventing downstream signaling that disrupts cell junctions.
• The FAF1-Hsp70 complex presents a potential therapeutic target for inhibiting tumorigenesis and metastasis.