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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels

Published on: May 18, 2009

Functional properties of five Dictyostelium discoideum P2X receptors

Abigail Baines1, Katie Parkinson1, Joan A Sim2

  • 1From the Faculty of Life Sciences and.

The Journal of Biological Chemistry
|June 7, 2013
PubMed

Insights

Dictyostelium discoideum P2X receptors function as ATP-gated channels in the contractile vacuole. Four of five P2X receptors (P2XA, P2XB, P2XD, P2XE) are ATP-gated, with P2XA being specific for ATP and showing impaired function in P2XA-deficient cells.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biochemistry

Background:

  • The Dictyostelium discoideum genome encodes five proteins homologous to vertebrate P2X receptors.
  • Unlike their vertebrate counterparts, these Dictyostelium P2X receptors are localized to the contractile vacuole, not the cell surface.

Purpose of the Study:

  • To investigate the function of Dictyostelium P2X receptors (P2XA-E) as ATP-gated channels.
  • To determine the influence of ionic and proton environments on receptor activity.
  • To assess the role of P2X receptors in osmoregulation.

Main Methods:

  • Humanized cDNAs of P2XA-E were expressed in human embryonic kidney cells.
  • Whole-cell patch-clamp electrophysiology was used to record membrane currents.
  • Experiments involved altering extracellular ionic and proton concentrations.
  • Phenotypic analysis of Dictyostelium lacking P2XA receptors was performed, followed by rescue experiments.

Main Results:

  • Four Dictyostelium P2X receptors (P2XA, P2XB, P2XD, P2XE) functioned as ATP-gated channels.
  • P2XA exhibited high specificity for ATP as an agonist.
  • Extracellular sodium inhibited ATP responses for P2XB, P2XD, and P2XE.
  • Proton concentration affected the desensitization and current amplitude of various P2X receptors.
  • P2XA-deficient Dictyostelium displayed impaired regulatory volume decrease, which was rescued by P2XA and P2XD.

Conclusions:

  • Dictyostelium P2X receptors function as ATP-gated ion channels within the contractile vacuole system.
  • P2XA plays a critical role in the regulatory volume decrease response to hypotonic stress.
  • Functional redundancy among Dictyostelium P2X receptors is limited, with P2XA and P2XD being key players in osmoregulation.
Keywords:
ATPDictyosteliumIon ChannelsOsmoregulationP2X ReceptorPurinergic AgonistsPurinergic ReceptorVacuolar Acidification

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