Identification of a tubulin binding motif on the P2X2 receptor

To isolate proteins interacting with P2X receptors, GST fusion proteins containing the intracellular C terminal tail of P2X2, P2X5, or P2X7 were used as bait to screen detergent extracts of rat brain synaptosomes. By SDS–PAGE combined with mass spectrometry, two interacting proteins were identified: βIII tubulin and myelin basic protein. While myelin basic protein bound to all three P2X subunits, βIII tubulin interacted exclusively with the P2X2 subunit. The tubulin binding domain could be confined to a proline-rich segment (amino acids 371–412) of the P2X2 subunit. Our results suggest a role for microtubules in the cellular localisation of the P2X2 receptor.