Regulation of the P2X7 receptor permeability to large molecules by extracellular Cl- and Na+

Qin Li, Xiang Luo, Shmuel Muallem

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Upon continuous stimulation, the pore of the monovalent cation-selective P2X7 receptor (P2X7R) expands to accommodate large molecules such as N-methyl-D-glucamine (NMDG+). How the change in P2X7R permeability is regulated is not known. Here we report that extracellular Cl- (Cl-o) regulates the outward current, whereas extracellular Na + (Na+ o) regulates the inward current of large molecules by P2X7Rs. The P2X7R-mediated current was measured in parotid acinar and duct cells of wild type and P2X7R-/- mice and in HEK293 cells expressing the human or mouse P2X7R isoforms. In symmetrical NaCl, triethylammonium chloride, and NMDG+ chloride solutions, the P2X7R current followed a linear current/voltage relationship. In symmetrical NaCl, removal of Cl- o reduced the inward Na+ current by ∼35% and the outward Na+ current by only 10%. By contrast, in the absence of Na+ i and the presence of Na + o or NMDG+ o, the removal of Cl - o reduced the inward Na+ or NMDG+ currents by 35% but the outward NMDG+ current by >95%. The effect of Cl- o was half-maximal at ∼60 mM. Reducing Cl - i from 150 to 10 mM did not reproduce the effects of Cl- o. All currents were eliminated in P2X7R-/- cells and reproduced by expressing the P2X7Rs in HEK cells. These findings suggest that Cl- o primarily regulates the outward P2X7R current of large molecules. When cells dialyzed with NMDG+ were stimulated in the presence of Na+ o, subsequent removal of Na+ o resulted in a strongly outward rectifying NMDG + current, indicating maintained high selectivity for Na+ over NMDG+. During continuous incubation in Na+-free medium, the permeability of the P2X7Rs to NMDG+ gradually increased. On the other hand, when the cells were incubated in symmetrical NMDG+ and only then stimulated with ATP, the NMDG+ current by P2X7Rs followed a linear current/voltage relationship and did not change with time. These findings suggest that the P2X7R has a "Na+ o memory" and that Na+ o regulates the inward permeability of P2X7Rs to large molecules. The novel regulation of P2X7R outward and inward permeability to large molecules by Cl- o and Na+ o, respectively, may have an important protective function, particularly in secretory epithelial cells.

Original languageEnglish (US)
Pages (from-to)26922-26927
Number of pages6
JournalJournal of Biological Chemistry
Volume280
Issue number29
DOIs
StatePublished - Jul 22 2005

Fingerprint

Purinergic P2X7 Receptors
Permeability
Molecules
Chlorides
Monovalent Cations
Acinar Cells
HEK293 Cells
Electric potential
Ducts
Protein Isoforms
Adenosine Triphosphate
Epithelial Cells
Cells

ASJC Scopus subject areas

  • Biochemistry

Cite this

Regulation of the P2X7 receptor permeability to large molecules by extracellular Cl- and Na+ . / Li, Qin; Luo, Xiang; Muallem, Shmuel.

In: Journal of Biological Chemistry, Vol. 280, No. 29, 22.07.2005, p. 26922-26927.

Research output: Contribution to journalArticle

@article{ee0f071a217d468db1bde351844476d1,
title = "Regulation of the P2X7 receptor permeability to large molecules by extracellular Cl- and Na+",
abstract = "Upon continuous stimulation, the pore of the monovalent cation-selective P2X7 receptor (P2X7R) expands to accommodate large molecules such as N-methyl-D-glucamine (NMDG+). How the change in P2X7R permeability is regulated is not known. Here we report that extracellular Cl- (Cl-o) regulates the outward current, whereas extracellular Na + (Na+ o) regulates the inward current of large molecules by P2X7Rs. The P2X7R-mediated current was measured in parotid acinar and duct cells of wild type and P2X7R-/- mice and in HEK293 cells expressing the human or mouse P2X7R isoforms. In symmetrical NaCl, triethylammonium chloride, and NMDG+ chloride solutions, the P2X7R current followed a linear current/voltage relationship. In symmetrical NaCl, removal of Cl- o reduced the inward Na+ current by ∼35{\%} and the outward Na+ current by only 10{\%}. By contrast, in the absence of Na+ i and the presence of Na + o or NMDG+ o, the removal of Cl - o reduced the inward Na+ or NMDG+ currents by 35{\%} but the outward NMDG+ current by >95{\%}. The effect of Cl- o was half-maximal at ∼60 mM. Reducing Cl - i from 150 to 10 mM did not reproduce the effects of Cl- o. All currents were eliminated in P2X7R-/- cells and reproduced by expressing the P2X7Rs in HEK cells. These findings suggest that Cl- o primarily regulates the outward P2X7R current of large molecules. When cells dialyzed with NMDG+ were stimulated in the presence of Na+ o, subsequent removal of Na+ o resulted in a strongly outward rectifying NMDG + current, indicating maintained high selectivity for Na+ over NMDG+. During continuous incubation in Na+-free medium, the permeability of the P2X7Rs to NMDG+ gradually increased. On the other hand, when the cells were incubated in symmetrical NMDG+ and only then stimulated with ATP, the NMDG+ current by P2X7Rs followed a linear current/voltage relationship and did not change with time. These findings suggest that the P2X7R has a {"}Na+ o memory{"} and that Na+ o regulates the inward permeability of P2X7Rs to large molecules. The novel regulation of P2X7R outward and inward permeability to large molecules by Cl- o and Na+ o, respectively, may have an important protective function, particularly in secretory epithelial cells.",
author = "Qin Li and Xiang Luo and Shmuel Muallem",
year = "2005",
month = "7",
day = "22",
doi = "10.1074/jbc.M504966200",
language = "English (US)",
volume = "280",
pages = "26922--26927",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "29",

}

TY - JOUR

T1 - Regulation of the P2X7 receptor permeability to large molecules by extracellular Cl- and Na+

AU - Li, Qin

AU - Luo, Xiang

AU - Muallem, Shmuel

PY - 2005/7/22

Y1 - 2005/7/22

N2 - Upon continuous stimulation, the pore of the monovalent cation-selective P2X7 receptor (P2X7R) expands to accommodate large molecules such as N-methyl-D-glucamine (NMDG+). How the change in P2X7R permeability is regulated is not known. Here we report that extracellular Cl- (Cl-o) regulates the outward current, whereas extracellular Na + (Na+ o) regulates the inward current of large molecules by P2X7Rs. The P2X7R-mediated current was measured in parotid acinar and duct cells of wild type and P2X7R-/- mice and in HEK293 cells expressing the human or mouse P2X7R isoforms. In symmetrical NaCl, triethylammonium chloride, and NMDG+ chloride solutions, the P2X7R current followed a linear current/voltage relationship. In symmetrical NaCl, removal of Cl- o reduced the inward Na+ current by ∼35% and the outward Na+ current by only 10%. By contrast, in the absence of Na+ i and the presence of Na + o or NMDG+ o, the removal of Cl - o reduced the inward Na+ or NMDG+ currents by 35% but the outward NMDG+ current by >95%. The effect of Cl- o was half-maximal at ∼60 mM. Reducing Cl - i from 150 to 10 mM did not reproduce the effects of Cl- o. All currents were eliminated in P2X7R-/- cells and reproduced by expressing the P2X7Rs in HEK cells. These findings suggest that Cl- o primarily regulates the outward P2X7R current of large molecules. When cells dialyzed with NMDG+ were stimulated in the presence of Na+ o, subsequent removal of Na+ o resulted in a strongly outward rectifying NMDG + current, indicating maintained high selectivity for Na+ over NMDG+. During continuous incubation in Na+-free medium, the permeability of the P2X7Rs to NMDG+ gradually increased. On the other hand, when the cells were incubated in symmetrical NMDG+ and only then stimulated with ATP, the NMDG+ current by P2X7Rs followed a linear current/voltage relationship and did not change with time. These findings suggest that the P2X7R has a "Na+ o memory" and that Na+ o regulates the inward permeability of P2X7Rs to large molecules. The novel regulation of P2X7R outward and inward permeability to large molecules by Cl- o and Na+ o, respectively, may have an important protective function, particularly in secretory epithelial cells.

AB - Upon continuous stimulation, the pore of the monovalent cation-selective P2X7 receptor (P2X7R) expands to accommodate large molecules such as N-methyl-D-glucamine (NMDG+). How the change in P2X7R permeability is regulated is not known. Here we report that extracellular Cl- (Cl-o) regulates the outward current, whereas extracellular Na + (Na+ o) regulates the inward current of large molecules by P2X7Rs. The P2X7R-mediated current was measured in parotid acinar and duct cells of wild type and P2X7R-/- mice and in HEK293 cells expressing the human or mouse P2X7R isoforms. In symmetrical NaCl, triethylammonium chloride, and NMDG+ chloride solutions, the P2X7R current followed a linear current/voltage relationship. In symmetrical NaCl, removal of Cl- o reduced the inward Na+ current by ∼35% and the outward Na+ current by only 10%. By contrast, in the absence of Na+ i and the presence of Na + o or NMDG+ o, the removal of Cl - o reduced the inward Na+ or NMDG+ currents by 35% but the outward NMDG+ current by >95%. The effect of Cl- o was half-maximal at ∼60 mM. Reducing Cl - i from 150 to 10 mM did not reproduce the effects of Cl- o. All currents were eliminated in P2X7R-/- cells and reproduced by expressing the P2X7Rs in HEK cells. These findings suggest that Cl- o primarily regulates the outward P2X7R current of large molecules. When cells dialyzed with NMDG+ were stimulated in the presence of Na+ o, subsequent removal of Na+ o resulted in a strongly outward rectifying NMDG + current, indicating maintained high selectivity for Na+ over NMDG+. During continuous incubation in Na+-free medium, the permeability of the P2X7Rs to NMDG+ gradually increased. On the other hand, when the cells were incubated in symmetrical NMDG+ and only then stimulated with ATP, the NMDG+ current by P2X7Rs followed a linear current/voltage relationship and did not change with time. These findings suggest that the P2X7R has a "Na+ o memory" and that Na+ o regulates the inward permeability of P2X7Rs to large molecules. The novel regulation of P2X7R outward and inward permeability to large molecules by Cl- o and Na+ o, respectively, may have an important protective function, particularly in secretory epithelial cells.

UR - http://www.scopus.com/inward/record.url?scp=22844435416&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=22844435416&partnerID=8YFLogxK

U2 - 10.1074/jbc.M504966200

DO - 10.1074/jbc.M504966200

M3 - Article

C2 - 15923180

AN - SCOPUS:22844435416

VL - 280

SP - 26922

EP - 26927

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 29

ER -