Purotoxin-1 – Ion Channels and Transporters

Purotoxin-1 (PT-1) is a peptide originally isolated from the Central Asian spider Geolycosa sp. Purotoxin-1 was shown to inhibit selectively P2X3 receptor channels at a 100 nM concentration. Studies were carried-out on cultured rat DRG neurons. Patch-clamp experiments did not show any inhibitory effect of PT-1 on voltage-gated channels (potentials range tested from -100 to 20 mV), neither on TRPV1 (after activation with 500 nM capsaicin). The selectivity of Purotoxin-1 for P2X3 was highlighted by activating this receptor with 10 μM ATP and 100 μM α, β Methylene-ATP. Indeed, unlike P2X3, P2X2 and heterodimer P2X2/3 are known to be not sensitive to such concentrations. Moreover, P2X3, P2X2, and P2X2/3 are the only known ATP-sensitive receptors expressed in plasma membranes of DRG neurons. So, the observed effect seems to be well related to a selective inhibition of P2X3. P2X3-mediated current was fully inhibited with 100 nM Purotoxin-1, making it the most potent and selective ligand for P2X3.

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