Direct observation of Piezo1 conformational states.

Abstract

PIEZOs are mechanosensitive ion channels that convert force into chemoelectrical signals. Mechanotransduction is thought to be initiated through the deformation of extensive arms of transmembrane domains emanating from a central ion-conducting pore. Structural studies show these arms adopt a symmetric bowl-shaped conformation, forming a dome of membrane that can be flatted and expanded by force. However, direct observation of channel conformation in a cell and an understanding of how the arms are engaged during mechanotransduction is lacking. Here, we use site-specific labeling and intramolecular fluorescent imaging to examine PIEZO1 conformation in a cell membrane. We show the arms of PIEZO1 are bent by the plasma membrane at rest and exhibit pronounced variation in flexibility along their length. Using stimuli which are known to modulate channel activity, we also show that the degree of arm extension from the central pore correlates with channel activation and inhibition. Our findings highlight how the cellular environment can shape PIEZO1 conformation and demonstrate a structure-function relationship between channel conformation and activation. More broadly, this study provides a basic understanding of how PIEZO1 senses mechanical force and presents a technical framework for the study of single-molecule protein conformation using direct nanoscopic imaging.