Inference of VEGFR2 dimerization kinetics on the cell surface by integrating single-molecule imaging and mathematical...

Area of Science:

• Cellular Biology
• Biophysics
• Biochemistry

Background:

• Receptor-receptor interactions are crucial for cell signaling initiation and modulation.
• Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) dimerization is essential for its signaling pathway.
• VEGFR2 interactions, including dimerization, occur even without ligand stimulation, necessitating kinetic quantification.

Purpose of the Study:

• To quantitatively determine the interaction kinetics of VEGFR2 on the cell surface in live cells.
• To compare the dimerization kinetics of full-length VEGFR2 (FLR2) with a truncated mutant (ECTM).
• To infer population-level receptor interaction kinetics from single-molecule imaging data.

Main Methods:

• Live-cell single-molecule imaging (SMI) to observe receptor interactions in real-time.
• Development of a stochastic mathematical model to simulate VEGFR2 diffusion and interactions.
• Model calibration using experimental measurements to determine kinetic parameters.

Main Results:

• A dimerization model sufficiently described VEGFR2 interactions in the absence of ligand.
• Full-length VEGFR2 (FLR2) exhibited a substantial fraction of dimers, while the truncated mutant (ECTM) was primarily monomeric.
• The dimer association rate constant was approximately ten times lower for ECTM compared to FLR2.

Conclusions:

• This study provides the first quantitative measurement of VEGFR2 interaction kinetics in live cells.
• The difference in dimerization between FLR2 and ECTM is mainly due to the dimer association rate.
• The combined approach of SMI and mathematical modeling is generalizable for in situ kinetic analysis of other cell surface proteins.