InterAKTions with FKBPs--mutational and pharmacological exploration

Area of Science:

• Molecular Biology
• Cell Signaling
• Cancer Research

Background:

• FKBP51 is an Hsp90 co-chaperone regulating kinases and steroid receptors.
• FKBP51 recruits PHLPP to dephosphorylate Akt, reducing chemoresistance in pancreatic cancer.
• The interaction between FKBP51 and Akt is crucial for cellular signaling pathways.

Purpose of the Study:

• To investigate the direct binding of FKBP51 and other FKBP family members to Akt.
• To elucidate the domains and conditions governing the FKBP51-Akt interaction.
• To determine the efficacy of FKBP51 inhibitors on the Akt-FKBP-PHLPP network.

Main Methods:

• Co-immunoprecipitation assays to detect protein complexes.
• Site-directed mutagenesis and domain mapping to identify interaction sites.
• Inhibition studies using FK506 analogs, Akt active site inhibitors, and allosteric Akt inhibitor VIII.
• Western blotting to assess Akt phosphorylation and downstream signaling.

Main Results:

• Multiple FKBP family members, including FKBP51, bind directly to Akt.
• FKBP51 interacts with Akt via multiple domains, independent of Akt's activation or phosphorylation status.
• FKBP51-Akt interaction is sensitive to Akt1 conformation but not FKBP51's FK506-binding pocket; allosteric Akt inhibitor VIII disrupted the interaction.
• FKBP51 inhibitors did not affect AktS473 phosphorylation or downstream targets.

Conclusions:

• FKBP51 directly binds Akt, both independently and via Hsp90.
• The FKBP51-Akt interaction is conformation-dependent and does not rely on the FKBP51 FK506-binding pocket.
• FKBP inhibitors are unlikely to modulate the Akt-FKBP-PHLPP signaling network effectively.