Quantification of integrin receptor agonism by fluorescence lifetime imaging

Area of Science:

• Cellular Biology
• Pharmacology
• Biophysics

Background:

• Assays for integrin-effector binding are lacking, hindering the development of effective integrin antagonists.
• Existing anti-integrin drugs have faced clinical failure due to secondary agonistic effects.

Purpose of the Study:

• To develop and validate a novel assay for quantifying integrin-effector interactions in living cells.
• To assess the response of these interactions to small molecule antagonists and identify potential agonistic activity.

Main Methods:

• Utilized fluorescence resonance energy transfer (FRET) combined with fluorescence lifetime imaging microscopy (FLIM).
• Expressed integrin-GFP and effector-mRFP pairs in living cells to measure protein-protein associations.
• Quantified the binding of talin to beta1 integrin and paxillin to alpha4 integrin.

Main Results:

• Demonstrated ligand and receptor activation-dependent association of integrins with effectors.
• Showed that small molecule RGD and LDV mimetics inhibit these interactions.
• Revealed agonistic activity of these small molecules, indicating potential for in vivo secondary effects.

Conclusions:

• The novel FRET-FLIM assay provides quantitative insights into integrin-effector binding dynamics.
• Findings highlight the importance of receptor conformation in the efficacy of small molecule integrin antagonists.
• The assay serves as a valuable tool for validating potential integrin antagonists and understanding their mechanisms of action.