An angstrom scale interaction between plasma membrane ATP-gated P2X 2 and α4β2 nicotinic channels measured with fluorescence resonance energy transfer and total internal reflection fluorescence microscopy

Abstract

Structurally distinct nicotinic and P2X channels interact functionally, such that coactivation results in cross-inhibition of one or both channel types. It is hypothesized, but not yet proven, that nicotinic and P2X channels interact at the plasma membrane. Here, we show that plasma membrane α4β2 nicotinic and P2X2 channels form a molecular scale partnership and also influence each other when coactivated, resulting in nonadditive cross-inhibitory responses. Total internal reflection fluorescence and fluorescence resonance energy transfer microscopy between fluorescently labeled P2X2 and α4β 2 nicotinic channels demonstrated close spatial arrangement of the channels in human embryonic kidney cells and in hippocampal neuron membranes. The data suggest that P2X2 and α4β2 channels may form a dimer, with the channels ∼80 Å apart. The measurements also show that P2X2 subunits interact specifically and robustly with the β2 subunits in α4β 2 channels. The data provide direct evidence for the close spatial apposition of full-length P2X2 and α4β 2 channels within 100 nm of the plasma membrane of living cells. Copyright © 2005 Society for Neuroscience.