Structure and Mechanogating of the Mechanosensitive PIEZO Channel

Abstract

The evolutionarily conserved PIEZO family of proteins, including PIEZO1 and PIEZO2, forms the long-sought bona fide mammalian mechanosensitive cation channel, and plays critical roles in various mechanotransduction processes such as touch, proprioception, tactile pain, vascular development and blood pressure regulation. Taking a multidisciplinary approach combining protein engineering and purification, cryo-EM, electrophysiology and drug screening, we have determined the three-bladed, propeller-like trimeric structures of both PIEZO1 and PIEZO2 that comprises 114 transmembrane helices (38 per protomer). Transmembrane helices 1-36 (TM1-36) are folded into nine tandem transmembrane helical units (THU) of four TMs each to form the unusual non-planar blades. The three blades are collectively curved into a nano-bowl shape of 28-nm diameter and 10-nm depth, with an extracellular cap-like structure embedded in the centre and a 9-nm-long intracellular beam connecting to the central pore. TM38 and the C-terminal domain are surrounded with the anchor domain and TM37, and enclose the central pore with both transmembrane and cytoplasmic constriction sites. Structural comparison between PIEZO1 and PIEZO2 has revealed that the transmembrane constriction site might act as a transmembrane gate. Structural and functional analyses have suggested that the PIEZO channel might employ the top cap to control the transmembrane gate, while the blade-beam might function as a lever-like apparatus to allosterically control the putative cytosolic gate, indicating a dual-gating mechanism. Together, our studies provide insights into the structure and mechanogating mechanism of PIEZO channels.