Spider venoms inhibit L-glutamate binding to brain synaptic membrane receptors.

Abstract

The venoms from three spider species, Araneus gemma, Neoscona arabesca, and Argiope aurantia, were shown to inhibit the high-affinity, sodium-independent L-glutamate-binding sites in rat brain synaptic membranes. The same three venoms caused concentration-dependent inhibition of the activity of the glutamate-binding glycoprotein purified from rat brain synaptic membranes. The venom milked from the glands of Araneus gemma was the most active inhibitor of L-glutamate binding, causing 60-80% inhibition of both synaptic membrane and purified protein binding activity at 0.01 unit. The inhibitory activity of this venom was associated with a single protein peak obtained from gel permeation chromatography of the venom. Finally, the effect of the venom from Araneus gemma on the synaptic membrane glutamate-binding sites was slowly reversible. These observations indicate that the spider venoms have a direct effect on the recognition sites for L-glutamic acid in brain synaptic membranes and that these sites are related to the physiologic glutamate receptors.The characterization of specific receptor sites with which Lglutamic acid interacts to produce excitation in vertebrate and invertebrate central nervous system neurons and in invertebrate neuromuscular junctions has been impeded by the lack of selective and potent antagonists of the excitatory activity of glutamate. A better definition of glutamate receptor sites in neurons may soon be possible due to recent observations by of the presence in spider venoms of selective antagonists of the L-glutamate excitatory activity detected in invertebrate neuromuscular junction and mammalian brain neuronal synapses. In the studies reported by Kawai et al. (1-3) the venom from two species of spiders, Nephila clavata and Araneus ventricosus, produced nearly identical inhibition of both neuronal pathway and L-glutamate-induced excitation at the lobster neuromuscular junction (1-3), a synaptic junction at which glutamate is thought to be the excitatory transmitter (4, 5).Several research groups have recently attempted to correlate the binding activity and selectivity of L-[3H]glutamatebinding sites in neuronal membranes with the characteristics of the physiologic L-glutamate receptors (e.g., refs. 6-10). In our previous studies we have concentrated on characterizing both the glutamate-binding sites and the glutamate-activated Na+ channels in mammalian brain synaptic membranes (11-15). We have also explored the biochemical features and binding activity and selectivity of a glutamate-binding glycoprotein purified from brain synaptic membranes (11-13). The binding activity of this purified protein and its sensitivity to various chemical treatments are very similar to the activity and sensitivity of the high-affinity L-glutamate-binding sites in synaptic membranes (11)(12)(13) MATERIALS AND METHODS Preparation of Synaptic Membranes and Measurement of L-[3H]Glutamate Binding. The synaptic plasma membranes used in these studies were purified from rat (male, SpragueDawley, Charles Ri...

Effects of the paratemnus elongatus pseudoscorpion venom in the uptake and binding of the L‐glutamate and GABA from rat cerebral cortex

“…The most powerful of them was A. gemma. It was used at a concentration of 0.01 U (amount obtained from a single venom gland), and it caused 60-80% inhibition of 3 H-L-glu binding in GBP or in membranes, and it also was 25 times more powerful than the venom of N. arabesca [38].…”

“…Nonspecific binding was determined in the presence of nonlabeled L-glu or GABA (from 10 −4 to 10 −7 M or from 10 −7 to 100 × 10 −4 M, respectively). Specific binding was determined by the subtraction of the averages of nonspecific binding [37,38]. Results were expressed as averages ± SEM of percentages of controls.…”

Characterization of L‐Glutamate Binding Sites in Rat Spinal Cord Synaptic Membranes: Evidence for Multiple Chloride Ion‐Dependent Sites

“…Although the C1--dependent binding site has been difficult to localize by autoradiography because it is destroyed by freezing (Fagg et al, 1983), it is the most thoroughly studied of ~G l u binding sites. Prior to the description of the specific effect of anions on L-G~u binding , assays were typically done using 50 mM Tris-HC1 buffer (Roberts, 1974;Michaelis et al, 1974;Foster and Roberts, 1978;Baudry and Lynch, 1979a). Thus, much of the earlier work is based on a mixed population of C1-dependent (predominant) and Cl--independent binding sites.…”

Biologically active phenol and indole derivatives of terrestrial arthropods: electrophysiological and chemical characteristics

“…A number of publications were devoted to a study of the molecular mechanisms of toxins' interaction of with the receptors. A protein named GBP was obtained from synaptic membranes that was able to bind glutamate [67,68]. It was demonstrated that the glutamate binding to this protein was inhibited by the reagents of the FeS groups -NaN 3 , KCN, chelating agents like the o-phenanthroline.…”