Essential control of an endothelial cell ISOC by the spectrin membrane skeleton

Endothelial responses to mechanical stress: where is the mechanosensor?

OBJECTIVE

The endothelium is normally subjected to mechanical deformation resulting from shear stress and from strain associated with stretch of the vessel wall. These stimuli are detected by a mechanosensor that initiates a variety of signaling systems responsible for triggering the functional responses. The identity of the mechanosensor has not been established. This article discusses the different mechanisms of mechanosensing that have been proposed and reviews the literature with respect to signaling systems that are activated in response to stress and strain in endothelium.

DATA SOURCES

Published literature related to mechanotransduction, signal transduction pathways initiated by strain in endothelium, and pathophysiologic effects of abnormal shear forces in diseases.

DATA EXTRACTION AND SYNTHESIS

Proposed mechanisms of mechanosensing include stretch-sensitive ion channels, protein kinases associated with the cytoskeleton, integrin-cytoskeletal interactions, cytoskeletal-nuclear interactions, and oxidase systems capable of generating reactive oxygen species. However, the molecular identity of the mechanosensor is not known, nor is it clear whether multiple sensing mechanisms exist.

CONCLUSIONS

Many responses are initiated in cells subjected to mechanical deformation, including alterations in ion channel conductance, activation of signal transduction pathways, and altered expression of specific genes. Future progress in this field will require a critical distinction between cell systems that become activated during mechanical strain and the identity of the cellular mechanosensor that triggers subsequent responses.

Ion transport proteins anchor and regulate the cytoskeleton

Structurally diverse ion transport proteins anchor the spectrin-actin cytoskeleton to the plasma membrane by binding directly to linker proteins of the ankyrin and protein 4.1 families. Cytoskeletal anchoring regulates cell shape and restricts the activity of ion transport proteins to specialised membrane domains. New directions are being forged by recent findings that localised anchoring by ion transport proteins regulates the ordered assembly of actin filaments and the actin-dependent processes of cell adhesion and motility.