ARGIOTOXIN DETECTS MOLECULAR DIFFERENCES IN AMPA RECEPTOR CHANNELS

Argiotoxin, a component of the spider venom from Argiope lobata, block s AMPA receptor channels expressed in homomeric and heteromeric config uration in Xenopus oocytes. Argiotoxin acts as an open channel blocker in a voltage-dependent manner and discriminates between the functiona lly diverse AMPA receptors. Importantly, a transmembrane region 2 dete rminant for divalent cation permeability also determines argiotoxin se nsitivity. Subunit-specific differences in the time courses of block a nd recovery demonstrate that heteromeric AMPA receptors can assemble i n variable ratios. Thus, argiotoxin can be used as a tool in analyzing the subunit composition of AMPA receptors in native membranes.