Pannexin 1 is the conduit for low oxygen tension-induced ATP release from human erythrocytes

Abstract

is the conduit for low oxygen tension-induced ATP release from human erythrocytes. Am J Physiol Heart Circ Physiol 299: H1146 -H1152, 2010. First published July 9, 2010; doi:10.1152/ajpheart.00301.2010.-Erythrocytes release ATP in response to exposure to the physiological stimulus of lowered oxygen (O 2) tension as well as pharmacological activation of the prostacyclin receptor (IPR). ATP release in response to these stimuli requires activation of adenylyl cyclase, accumulation of cAMP, and activation of protein kinase A. The mechanism by which ATP, a highly charged anion, exits the erythrocyte in response to lowered O 2 tension or receptor-mediated IPR activation by iloprost is unknown. It was demonstrated previously that inhibiting pannexin 1 with carbenoxolone inhibits hypotonically induced ATP release from human erythrocytes. Here we demonstrate that three structurally dissimilar compounds known to inhibit pannexin 1 prevent ATP release in response to lowered O 2 tension but not to iloprost-induced ATP release. These results suggest that pannexin 1 is the conduit for ATP release from erythrocytes in response to lowered O 2 tension. However, the identity of the conduit for iloprost-induced ATP release remains unknown.iloprost; carbenoxolone; probenecid; red blood cell; cystic fibrosis transmembrane conductance regulator ERYTHROCYTES CONTRIBUTE to the regulation of vascular caliber by virtue of their ability to release adenosine 5=-triphosphate (ATP) (14 -17, 48, 50). ATP released from erythrocytes binds to purinergic receptors on the vascular endothelium, which leads to the local formation of endothelium-derived vasodilators such as nitric oxide, prostaglandins, and endotheliumderived hyperpolarizing factor (20,46,50).Erythrocytes release ATP in response to mechanical deformation and exposure to lowered oxygen (O 2 ) tension and in response to incubation with pharmacological agents such as the prostacyclin analog iloprost (Ilo) (5,44,45). ATP release in response to these various stimuli requires activation of adenylyl cyclase, accumulation of cAMP, and activation of PKA (3,43,47). Although several components of the signaling pathway for ATP release from erythrocytes have been investigated, the identity of the conduit by which ATP exits these cells is not fully characterized. In other cell types, several membrane channels, including connexin hemichannels, voltage-dependent anion channels, volume-regulated anion channels, and ATP-binding cassette proteins, have been implicated as conduits for ATP release (2,27,29,37,40,41). In addition, the cystic fibrosis transmembrane conductance regulator (CFTR), an ATP-binding cassette protein required for ATP release from erythrocytes in response to mechanical deformation (25, 45), was once considered to be a possible ATP conduit in cells. However, more recent studies demonstrate that CFTR is not likely to serve as an ATP conduit itself but rather regulates other channels that serve that role (1,7,19,24,51).Recently, the protein family of pannexins, orthologs of the invert...

Pannexin channels are not gap junction hemichannels

“…natural conditions in cells endogenously expressing Panx1 such as CNS pyramidal 17,35 and Purkinje neurons, 18 erythrocytes, [19][20][21] T-cells, 22 astrocytes, 23 airway epithelial cells, 24 taste cells 25 and cochlear supporting cells. 26 Functional properties previously attributed to connexin hemichannels may be valid, but may need to be re-addressed in light of these pannexin findings.…”

Pannexins in ischemia-induced neurodegeneration

“…ATP efflux from erythrocytes through Px1 channels under hypoxic conditions may induce vasodilation (13,14). In apoptotic lymphocytes, ATP release through Px1 channels was reported to serve as a "find-me" signal for attracting macrophages (15).…”

Bacterial RTX Toxins Allow Acute ATP Release from Human Erythrocytes Directly through the Toxin Pore

“…Several ATP exit pathways have been suggested for non-lytic ATP release from erythrocytes including the cystic fibrosis transmembrane conductance regulator (CFTR) 2 (10,15), pannexin 1 (9,16), and recently, the voltage-dependent anion channel (VDAC) (14). Hence, hypotonic stress and low O 2 tensioninduced ATP release from human erythrocytes were described to depend on pannexin 1 (9,16).…”

“…Hence, hypotonic stress and low O 2 tensioninduced ATP release from human erythrocytes were described to depend on pannexin 1 (9,16). CFTR has been suggested to be necessary for ATP release upon mechanical deformation (10) as well as low O 2 and prostacyclin stimulation (16).…”

“…Hence, hypotonic stress and low O 2 tensioninduced ATP release from human erythrocytes were described to depend on pannexin 1 (9,16). CFTR has been suggested to be necessary for ATP release upon mechanical deformation (10) as well as low O 2 and prostacyclin stimulation (16). It is, however, now recognized that CFTR is more likely to regulate other channels and not being directly involved in ATP release itself (17)(18)(19)(20)(21).…”