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Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region.

ABSTRACT: Ligand-gated ion channels are partially activated by their ligands, resulting in currents lower than the currents evoked by the physiological full agonists. In the case of P2X purinergic receptors, a cation-selective pore in the transmembrane region expands upon ATP binding to the extracellular ATP-binding site, and the currents evoked by ?,?-methylene ATP are lower than the currents evoked by ATP. However, the mechanism underlying the partial activation of the P2X receptors is unknown although the crystal structures of zebrafish P2X4 receptor in the apo and ATP-bound states are available. Here, we observed the NMR signals from M339 and M351, which were introduced in the transmembrane region, and the endogenous alanine and methionine residues of the zebrafish P2X4 purinergic receptor in the apo, ATP-bound, and ?,?-methylene ATP-bound states. Our NMR analyses revealed that, in the ?,?-methylene ATP-bound state, M339, M351, and the residues that connect the ATP-binding site and the transmembrane region, M325 and A330, exist in conformational equilibrium between closed and open conformations, with slower exchange rates than the chemical shift difference (<100 s(-1)), suggesting that the small population of the open conformation causes the partial activation in this state. Our NMR analyses also revealed that the transmembrane region adopts the open conformation in the state bound to the inhibitor trinitrophenyl-ATP, and thus the antagonism is due to the closure of ion pathways, except for the pore in the transmembrane region: i.e., the lateral cation access in the extracellular region.

SUBMITTER: Minato Y

PROVIDER: S-EPMC4855573 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region.

Minato Yuichi Y Suzuki Shiho S Hara Tomoaki T Kofuku Yutaka Y Kasuya Go G Fujiwara Yuichiro Y Igarashi Shunsuke S Suzuki Ei-Ichiro E Nureki Osamu O Hattori Motoyuki M Ueda Takumi T Shimada Ichio I

Proceedings of the National Academy of Sciences of the United States of America 20160411 17

Ligand-gated ion channels are partially activated by their ligands, resulting in currents lower than the currents evoked by the physiological full agonists. In the case of P2X purinergic receptors, a cation-selective pore in the transmembrane region expands upon ATP binding to the extracellular ATP-binding site, and the currents evoked by α,β-methylene ATP are lower than the currents evoked by ATP. However, the mechanism underlying the partial activation of the P2X receptors is unknown although ...[more]

PMID: 27071117

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Dataset Information

Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region.

Publications

Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region.

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