Measuring ligand-receptor binding kinetics and dynamics using k-space image correlation spectroscopy

TL;DR

This paper extends the k-space image correlation spectroscopy (kICS) technique to measure binding kinetics of biomolecules, enabling analysis of ligand-receptor interactions and receptor state interconversions from fluorescence microscopy data.

Contribution

The authors develop a mathematical framework for kICS to quantify kinetic binding rates and demonstrate its application on real biological systems.

Findings

kICS can measure ligand-receptor binding rates.

The method accurately extracts molecular transport coefficients.

Application to real data shows kICS's effectiveness in biological systems.

Abstract

Accurate measurements of kinetic rate constants for interacting biomolecules is crucial for understanding the mechanisms underlying intracellular signalling pathways. The magnitude of binding rates plays a very important molecular regulatory role which can lead to very different cellular physiological responses under different conditions. Here, we extend the k-space image correlation spectroscopy (kICS) technique to study the kinetic binding rates of systems wherein: (a) fluorescently labelled, free ligands in solution interact with unlabelled, diffusing receptors in the plasma membrane and (b) systems where labelled, diffusing receptors are allowed to bind/unbind and interconvert between two different diffusing states on the plasma membrane. We develop the necessary mathematical framework for the kICS analysis and demonstrate how to extract the elevant kinetic binding parameters of the underlying molecular system from fluorescence video-microscopy image time-series. Finally, by examining real data for two model experimental systems, we demonstrate how kICS can be a powerful tool to measure molecular transport coefficients and binding kinetics.