Piezo1 regulates mechanotransductive release of ATP from human RBCs

Abstract

Piezo proteins (Piezo1 and Piezo2) are recently identified mechanically activated cation channels in eukaryotic cells and associated with physiological responses to touch, pressure, and stretch. In particular, human RBCs express Piezo1 on their membranes, and mutations of Piezo1 have been linked to hereditary xerocytosis. To date, however, physiological functions of Piezo1 on normal RBCs remain poorly understood. Here, we show that Piezo1 regulates mechanotransductive release of ATP from human RBCs by controlling the shear-induced calcium (Ca 2+ ) influx. We find that, in human RBCs treated with Piezo1 inhibitors or having mutant Piezo1 channels, the amounts of shear-induced ATP release and Ca 2+ influx decrease significantly. Remarkably, a critical extracellular Ca 2+ concentration is required to trigger significant ATP release, but membrane-associated ATP pools in RBCs also contribute to the release of ATP. Our results show how Piezo1 channels are likely to function in normal RBCs and suggest a previously unidentified mechanotransductive pathway in ATP release. Thus, we anticipate that the study will impact broadly on the research of red cells, cellular mechanosensing, and clinical studies related to red cell disorders and vascular disease. Previous studies have shown that the addition of chemicals that stiffen RBC membranes decreases the amount of ATP released (9, 16), indicating that deformation of the cell membrane is a necessary trigger. In addition, biological mediators, such as cystic fibrosis transmembrane conductance regulator (CFTR) and pannexin-1 hemichannels, are involved in the release pathways of mechanotransductive ATP release from RBCs (9,14,17,18). Inhibition of CFTR leads to an impaired ATP release from deformed RBCs (14). Recent studies, including our previous findings, suggest that interactions between membrane-associated actin and CFTR play important roles in the mechanotransductive ATP release from RBCs (9, 17). Pannexin-1, however, is a channel-forming protein and has been suggested as a mechanosensing ATP release channel (18). Under osmotic stress, for example, ATP released from RBCs was attenuated by carbenoxolone, a highly effective pannexin channel blocker, suggesting that pannexin-1 might be one of the conductance channels responsible for the mechanotransductive release of ATP (18). Although progress has been made in understanding mechanotransductive ATP release from RBCs, many questions remain about the signal transduction pathways. For example, how does mechanical force transduce signals to ATP release channels? Are there any stretch-activated ion channels on RBCs that may sense mechanical forces and activate ATP release? If so, are there any secondary messengers that could be generated by mechanical stimuli and regulate ATP release?Piezo proteins (Piezo1 and Pizeo2) are recently identified mechanically activated cation channels in mammals (19,20) and can be fully activated without involvement of additional proteins (20, 21). Piezo-induced cationic currents were first observe...

Purinergic Signaling in the Cardiovascular System

“…ATP is released from human erythrocytes in response to mechanical deformation or hypoxia. 107 Erythrocytes are not only O 2 carriers but also ATP release via pannexin 1 hemichannels has a direct role in regulation of vascular tone.…”

New insights on hereditary erythrocyte membrane defects

“…This protein has been identified in the RBC membrane, and in mice it has been shown to form a tetramer of about 1.2 million daltons; it is therefore the largest ion channel identified to date, and moreover it regulates mechanotransductive release of ATP from human RBCs. [40][41][42][43] The identified mutations are missense and mainly located in the highly conserved C-terminus of the protein, recently described to form the pore of the channel. 44 Several electrophysiology studies demonstrated that the mutations cause a gain-of-function phenotype with delayed inactivation of the channel, 38,39,45 sugUpdate of the red cell membrane disorders haematologica | 2016; 101 (11)gesting increased cation permeability leads to DHS erythrocyte dehydration.…”

Endothelial cation channel PIEZO1 controls blood pressure by mediating flow-induced ATP release

“…Volume 126 Number 12 December 2016 studies using urothelial cells and red blood cells have also shown a PIEZO1-mediated mechanotransductive release of ATP, indicating that this is a cellular mechanism not restricted to endothelial cells (48,49). However, the process of PIEZO1-mediated ATP release from endothelial cells appears to involve additional mechanisms that still need to be fully explored.…”