# The Notch1 intracellular domain orchestrates mechanotransduction of fluid shear stress

## TL;DR

This study reveals how fluid shear stress activates the Notch1 receptor through a unique mechanism involving receptor polarization and endocytosis.

## Contribution

The paper identifies a flow-specific Notch1 activation mechanism distinct from canonical ligand trans-endocytosis.

## Key findings

- Unidirectional flow polarizes Notch1 receptors into microdomains, leading to cis-endocytosis.
- The Notch1 intracellular domain is essential for flow-induced receptor polarization and cleavage.
- Shear stress enhances interactions with annexin A2 and caveolar proteins to drive Notch1 activation.

## Abstract

Fluid shear stress mechanotransduction by Notch1: flow stimulates Notch1 intracellular domain interactions to polarize receptors into microdomains, driving endocytosis and proteolytic activation.

Hemodynamic shear stress regulates endothelial phenotype through activation of Notch1 signaling, yet the mechanistic basis for this activation is unclear. Here, we establish a fluid shear stress–dependent mechanism of Notch1 activation that is distinct from canonical ligand trans-endocytosis. Application of unidirectional laminar flow triggers the rapid spatial polarization of full-length Notch1 heterodimers into downstream membrane microdomains. Unlike canonical transactivation, Notch1 receptors are cis-endocytosed into the receptor-bearing cell within polarized microdomains. We discover that the Notch1 intracellular domain critically orchestrates receptor polarization and proteolytic cleavage in response to flow, but is dispensable for canonical ligand transactivation. Shear stress increases intracellular domain interaction with annexin A2 and caveolar proteins, which control Notch1 cis-endocytosis and proteolytic activation. These findings define a flow-specific Notch1 mechanotransduction mechanism linking receptor polarization and endocytosis with proteolytic activation and illuminate a new pathway by which mechanical forces integrate with Notch receptor activation.