Huwentoxin

Huwentoxins (HWTX) are a group of neurotoxic peptides found in the venom of the Chinese bird spider Haplopelma schmidti.

[1] While structural similarity can be found among several of these toxins, HWTX as a group possess high functional diversity.

[13] Cytosolic Ca2+ overload is one of the primary factors for inflammatory cells activation, therefore Ca2+ channel blockers can have a potential role as an anti-inflammatory drug.

[15] HWTX-X shows little homology with other huwentoxins, however, it can cause reversible blockage of N-type Ca2+ channels in rat dorsal root ganglion cells under whole-cell voltage clamp conditions.

It does show more than 50% homology with the toxin Ptu1 from the assassin bug Peirates turpis and ω-conotoxin SVIA from the Conus striatus, two N-type Ca2+ blockers.

HWTX-X specifically blocks GVIA-sensitive, N-type Ca2+ channels in rat dorsal root ganglion cells.

[15] HWTX-II is an insecticidal peptide and is structurally unusual compared to the other HWTX in that it lacks the typical ICK motif.

[19] HWTX-II blocks neuromuscular transmission in the isolated mouse nerve diaphragm preparation and acts cooperatively to potentiate the activity of HWTX I.

HWTX-III showed no effect on the activation and inactivation kinetics of the insect neuron VGSCs, and also no change in the ion selectivity of the channels.

[21] HWTX-III is able to enhance smooth muscle reactions elicited by nerve stimulation of the isolated rat vas deferens.

HWTX-IV comprises 35 amino acid residues, with three disulfide bridges, belonging to the ICK motif structural family.

HWTX-IV inhibits these channels by binding to receptor site 4 and trapping the domain II voltage sensor in the closed configuration.

[23] HWTX-VII and HWTX-VIII are insecticidal peptides with amino acid sequences and bioactivities similar to that of HWTX-II.

[24] Both HWTX-VII and HWTX-VIII block neuromuscular transmission in the isolated mouse phrenic nerve-diaphraghm preparation and act cooperatively with HWTX-I.