P2X Receptors

The main points: The P2X receptor is ionotropic. When ATP binds to a P2X receptor, Ca2+ rushes into the cell.

The structure of P2X receptors (ionotropic) is unusually simple. Each subunit has only two transmembrane domains, and only three of these subunits are required to form a trimeric receptor.

[Image: wikipedia]

Seven separate genes coding for P2X subunits, named P2X₁ through P2X₇, have been identified. Only some combinations of three subunits are used to build this trimeric receptor, e.g. P2X₇ homomeric, and P2X_1/5 heteromeric receptors. Functional P2X6 homomeric and P2X7 heteromeric receptor cannot be formed.

Although the P2X pore forms a nonselective cation channel, it is especially permeable to calcium.

This receptor mediates excitatory postsynaptic responses.

They are widely distributed in CNS and PNS neurons.

P2X receptors are also present on astrocytes.

They may play a role in mechanosensation and pain in sensory nerves, but their function in most other cells is not known.