Measuring Integrin Force Loading Rates Using a Two-Step DNA Tension Sensor.

Area of Science:

• Cell biology
• Biophysics
• Molecular mechanotransduction

Background:

• Cell-extracellular matrix (ECM) forces are mediated by integrin receptors and crucial for cell functions.
• Molecular Tension Fluorescence Microscopy (MTFM) measures integrin-ECM forces but struggles to characterize force dynamics like loading rate.
• Understanding force loading rate is vital for receptor signaling and adhesion formation.

Purpose of the Study:

• To develop a novel probe for measuring the force loading rate (LR) of integrin-ECM interactions in live cells.
• To characterize the force dynamics and bond lifetime of engaged integrin receptors.

Main Methods:

• Engineered a DNA probe with two distinct force-induced mechanical transitions (4.7 pN and 47 pN).
• Utilized single-molecule fluorescence microscopy to observe probe transitions in live cells.
• Applied automated analysis to thousands of force events across multiple cells.

Main Results:

• Quantified integrin bond lifetime decaying exponentially (τ = 45.6 s) for forces >4.7 pN.
• Identified a subset of interactions maturing to >47 pN with a median loading rate of 1.1 pN s⁻¹.
• Observed these higher force events primarily at the cell periphery.

Conclusions:

• The developed LR probe successfully measures force loading rates in live cells.
• This tool provides new insights into the dynamics of cell-matrix force transmission.
• The modular probe design can be adapted for studying various mechanoreceptors and cell models.