Philanthotoxin

Philanthotoxins are components of the venom of the Egyptian solitary wasp Philanthus triangulum, commonly known as the European beewolf. Philanthotoxins are polyamine toxins, a group of toxins isolated from the venom of wasps and spiders which immediately but reversibly paralyze their prey. δ-philanthotoxin, also known as PhTX-433, is the most active philanthotoxin that can be refined from the venom. PhTX-433 functions by non-selectively blocking excitatory neurotransmitter ion channels, including nicotinic acetylcholine receptors (nAChRs) and ionotropic glutamate receptors (iGluRs). Synthetic analogues, including PhTX-343 and PhTX-12, have been developed to improve selectivity. While the IC50 values of philanthotoxins varies between analogues and receptor subunit composition, the IC50 value of PhTX-433 at the iGluR AMPA receptor naturally expressed in locust leg muscle is 18 μM and the IC50 value at rat nAChRs is 1 μM.

== Biological context == thumb|European beewolf female with paralyzed prey intended for her offspring|alt=|left Nesting female Philanthus triangulum wasps utilize philanthotoxin-containing venom to paralyze prey (generally working honey bees Apis mellifera though other species may be collected) by stinging directly behind the front legs through the articular membranes. The female then carries the paralyzed prey to her nest burrow to be fed to her brood. The ability of the philanthotoxins in the venom to paralyze insect skeletal muscle through the blocking of glutamate receptor ion channels allows for this process to occur. Larval wasps rely on the paralyzed bees as a food source when they emerge. Paralyzed bee-prey may be stored for some length of time within the burrow and are regularly provisioned by the mother wasp to avoid spoiling due to fungal or bacterial infestation. In other predatory wasp species that paralyze instead of immediately killing the prey they provide their offspring, spoilage is deferred significantly by the chemical process of paralysis. Analysis of the provisioning of bee-prey by Beewolves, however, found that paralysis alone was not sufficient to prevent spoilage, and that additional preservation methods were associated with treatment by the female wasp.