Rapid signal transduction in living cells is a unique feature of mechanotransduction

TLDR

Mechanotransduction is thought to begin at the force–membrane interface through protein conformational changes, but prior studies have lacked the temporal resolution to test this hypothesis. The authors used a FRET‑based cytosolic Src reporter and nanometer‑scale cytoskeletal deformation imaging to show that integrin‑activated stress rapidly activates Src via microtubule‑mediated transmission. They found that mechanical stress (<0.3 s) triggers remote Src activation dependent on cytoskeletal prestress, whereas soluble EGF does not, and that a 1.8‑Pa stress elicits Src activation comparable to 0.4 ng/ml EGF over minutes, demonstrating rapid, unique signal transduction through the prestressed cytoskeleton.

Abstract

It is widely postulated that mechanotransduction is initiated at the local force–membrane interface by inducing local conformational changes of proteins, similar to soluble ligand-induced signal transduction. However, all published reports are limited in time scale to address this fundamental issue. Using a FRET-based cytosolic Src reporter in a living cell, we quantified changes of Src activities as a local stress via activated integrins was applied. The stress induced rapid (&lt;0.3 s) activation of Src at remote cytoplasmic sites, which depends on the cytoskeletal prestress. In contrast, there was no Src activation within 12 s of soluble epidermal growth factor (EGF) stimulation. A 1.8-Pa stress over a focal adhesion activated Src to the same extent as 0.4 ng/ml EGF at long times (minutes), and the energy levels for mechanical stimulation and chemical stimulation were comparable. The effect of both stress and EGF was less than additive. Nanometer-scale cytoskeletal deformation analyses revealed that the strong activation sites of Src by stress colocalized with large deformation sites of microtubules, suggesting that microtubules are essential structures for transmitting stresses to activate cytoplasmic proteins. These results demonstrate that rapid signal transduction via the prestressed cytoskeleton is a unique feature of mechanotransduction.