Heteromeric channels with different phenotypes are generated when coexpressing two P2X2 receptor isoforms.

Area of Science:

• Molecular Biology
• Neuroscience
• Biophysics

Background:

• P2X2 receptors are ligand-gated ion channels involved in neurotransmission.
• Alternative splicing of P2X2 receptors generates different isoforms with potentially distinct properties.
• Understanding heteromeric channel formation is crucial for elucidating receptor function.

Purpose of the Study:

• To investigate the formation of heteromeric channels from P2X2 receptor isoforms during co-expression.
• To determine if co-expression leads to novel channel stoichiometries with altered ATP sensitivity.
• To explore the functional consequences of P2X2 receptor isoform assembly.

Main Methods:

• Heterologous co-expression of P2X2 receptor isoforms in Xenopus laevis oocytes.
• Two-electrode voltage-clamp technique to measure ATP-induced currents.
• Analysis of ATP sensitivity (EC50) and Hill coefficients to characterize channel properties.

Main Results:

• Co-expression of P2X2-1a and P2X2-2bm isoforms resulted in two distinct populations of oocytes with differing ATP sensitivities and Hill coefficients.
• These populations corresponded to specific heteromeric stoichiometries (2:1 and 1:2 isoform ratios).
• Homomeric channel expression did not account for the observed differences, supporting heteromeric assembly.

Conclusions:

• Two distinct heteromeric P2X2 receptor channels can be assembled from the P2X2-1a and P2X2-2bm isoforms.
• The findings support a model where ATP activation of two subunits opens P2X2 channels.
• PPADS inhibition suggests binding to all three subunits of P2X2 receptors.