PIEZO1 functions as a potential oncogene by promoting cell proliferation and migration in gastric carcinogenesis

Mechanotransduction plays a crucial role in physiology. Biological processes including sensing touch and sound waves require yet unidentified cation channels that detect pressure. Mouse piezo1 (mpiezo1) and mpiezo2 induce mechanically activated cationic currents in cells; however, it is unknown if piezos are pore-forming ion channels or modulate ion channels. We show that Drosophila piezo (dpiezo) also induces mechanically activated currents in cells, but through channels with remarkably distinct pore properties including sensitivity to the pore blocker ruthenium red and single channel conductances. mpiezo1 assembles as a ~1.2 million-Dalton tetramer, with no evidence of other proteins in this complex. Finally, purified mpiezo1 reconstituted into asymmetric lipid bilayers and liposomes forms ruthenium red-sensitive ion channels. These data demonstrate that piezos are an evolutionarily conserved ion channel family involved in mechanotransduction.

Despite acting as a barrier for the organs they encase, epithelial cells turnover at some of the fastest rates in the body. Yet, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How do the number of dying cells match those dividing to maintain constant numbers? We previously found that when epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die 1 . Conversely, what controls epithelial cell division to balance cell death at steady state? Here, we find that cell division occurs in regions of low cell density, where epithelial cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the same Piezo1 channel. To do so, stretch triggers cells paused in early G2 to activate calcium-dependent ERK1/2 phosphorylation that activates cyclin B transcription necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at steady state, the type of mechanical force controls the outcome: stretch induces cell division whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated since it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions where cells divide, Piezo1 localizes to the plasma membrane and cytoplasm whereas in dense regions where cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion/apoptosis in crowded regions and cell division in sparse regions.

Arterial blood pressure is controlled by vasodilatory factors such as nitric oxide (NO) that are released from the endothelium under the influence of fluid shear stress exerted by flowing blood. Flow-induced endothelial release of ATP and subsequent activation of Gq/G11-coupled purinergic P2Y2 receptors have been shown to mediate fluid shear stress-induced stimulation of NO formation. However, the mechanism by which fluid shear stress initiates these processes is unclear. Here, we have shown that the endothelial mechanosensitive cation channel PIEZO1 is required for flow-induced ATP release and subsequent P2Y2/Gq/G11-mediated activation of downstream signaling that results in phosphorylation and activation of AKT and endothelial NOS. We also demonstrated that PIEZO1-dependent ATP release is mediated in part by pannexin channels. The PIEZO1 activator Yoda1 mimicked the effect of fluid shear stress on endothelial cells and induced vasorelaxation in a PIEZO1-dependent manner. Furthermore, mice with induced endothelium-specific PIEZO1 deficiency lost the ability to induce NO formation and vasodilation in response to flow and consequently developed hypertension. Together, our data demonstrate that PIEZO1 is required for the regulation of NO formation, vascular tone, and blood pressure.