Neuroactive Toxins of Spider Venoms

Abstract

A variety of neuroactive toxins have been found in the venom of spiders. The venom of Latrodectus mactans(black widow spider) is known as a potent neurotoxin, fatal to humans and animals. The effective component, α-latrotoxin (Mr=130,000) acts on the nerve terminals, causing massive release of transmitters and depletion of the synaptic vesicles, by inducing influx of cations such as Ca²⁺and Na⁺through the channels existing in the presynaptic nerve terminals.

In the venom of Araneidspiders, a different type of toxin from the black widow spider venom was found. Joro spider toxin (JSTX) from Nephila clavat, NSTX from Nephila maculata, and argiopine (argiotoxin) from Argiope lobataact postsynaptically on glutamate receptors. These toxins share a common structure of a phenolic moiety connected to a polyamine. Chemical synthesis of these low molecular weight toxins has enabled morphological and biochemical studies of the glutamate receptors.

Recently, a third group of neurotoxins was found in genus Agelenidae. A number of toxins isolated from the venom of Agelenopsis aperta, Hololena curtaand Agelena opulentawere found to block synaptic transmission by a presynaptic mechanism. The structures of a number of Agelenidaetoxins have been characterized, and it has been shown that they block presynaptic calcium channels. These toxins should serve as useful tools for isolating and characterizing neuronal calcium channel proteins.