Pore properties and pharmacological features of the P2X receptor channel in airway ciliated cells.
Airway ciliated cells express an ATP-gated P2X receptor channel of unknown subunit composition (P2X(cilia)) which is modulated by Na+ and by long exposures to ATP. P2X(cilia) was investigated by recording currents from freshly dissociated rabbit airway ciliated cells with the patch-clamp technique in the whole-cell configuration. During the initial continuous exposure to extracellular ATP, P2X(cilia) currents gradually increase in magnitude (priming), yet the permeability to N-methyl-D-glucamine (NMDG) does not change, indicating that priming does not arise from a progressive change in pore diameter. Na+, which readily permeates P2X(cilia) receptor channels, was found to inhibit the channel extracellular to the electric field. The rank order of permeability to various monovalent cations is: Li+, Na+, K+, Rb+, Cs+, NMDG+ and TEA+, with a relative permeability of 1.35, 1.0, 0.99, 0.91, 0.79, 0.19 and 0.10, respectively. The rank order for the alkali cations follows an Eisenman series XI for a high-strength field site. Ca2+ has been estimated to be 7-fold more permeant than Na+. The rise in [Ca2+]i in ciliated cells, induced by the activation of P2X(cilia), is largely inhibited by either Brilliant Blue G or KN-62, indicating that P2X7 may be a part of P2X(cilia). P2X(cilia) is augmented by Zn2+ and by ivermectin, and P2X4 receptor protein is detected by immunolabelling at the basal half of the cilia, strongly suggesting that P2X4 is a component of P2X(cilia) receptor channels. Taken together, these results suggest that P2X(cilia) is either assembled from P2X4 and P2X7 subunits, or formed from modified P2X4 subunits.
Ma
Weiyuan
W
Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva.
Korngreen
Alon
A
Weil
Simy
S
Cohen
Enbal Ben-Tal
EB
Priel
Avi
A
Kuzin
Liubov
L
Silberberg
Shai D
SD
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002586:Cesium / Q000378:metabolism; D002923:Cilia / Q000187:drug effects / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism; D007559:Ivermectin / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D012964:Sodium / Q000378:metabolism; D014132:Trachea / Q000187:drug effects / Q000378:metabolism*
D007473:Ion Channels; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D002586:Cesium; C063302:KN 62; D007559:Ivermectin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium