Insecticidal toxins from black widow spider venom

Area of Science:

• Biochemistry
• Neuroscience
• Toxicology

Background:

• Latrodectus spider venom exhibits similar biological effects across diverse animal phyla.
• These effects are mediated by distinct phylum-specific neurotoxins, collectively termed latrotoxins, with molecular masses of 110–140 kDa.

Purpose of the Study:

• To investigate the structural and functional characteristics of latrotoxins.
• To understand the mechanisms by which latrotoxins interact with nerve terminals and cell membranes.

Main Methods:

• Analysis of latrotoxin structures, including three-dimensional (3D) structure determination.
• Investigation of toxin-receptor interactions and membrane pore formation.

Main Results:

• Five insecticidal toxins (latroinsectotoxins, LITs), a vertebrate-specific neurotoxin (alpha-latrotoxin, alpha-LTX), and a crustacean toxin (alpha-latrocrustatoxin, alpha-LCT) have been identified.
• Latotoxins stimulate massive neurotransmitter release by binding receptors and forming ion-permeable pores.
• Elucidated LTX structures (alpha-LIT, delta-LIT, alpha-LTX, alpha-LCT) show high homology with a unique N-terminal sequence and ankyrin repeats.
• Alpha-LTX forms dimers and tetramers; only tetramers insert into membranes and form pores.
• Preliminary 3D reconstruction of delta-LIT monomer shows spatial similarity to alpha-LTX monomer.

Conclusions:

• Latotoxins share conserved structural features and mechanisms of action, despite phylum-specific targeting.
• The dimeric and tetrameric nature of latotoxins is crucial for their membrane pore-forming activity.
• Understanding latotoxin function provides insights into neurotoxin action and potential therapeutic targets.