Molecular Diversity of Peptide Toxins in the Venom of Spider as Revealed by cDNA Library and Transcriptome Sequencing Analysis.

The venoms of toxic animals are chemical pools composed of various proteins, peptides, and small organic molecules used for predation and defense, in which the peptidic toxins have been intensively pursued mining modulators targeting disease-related ion channels and receptors as valuable drug pioneers. In the present study, we uncovered the molecular diversity of peptide toxins in the venom of the spider by using a combinatory strategy of venom gland cDNA library and transcriptome sequencing (RNA-seq). An amount of 991 high-quality expressed sequence tags (ESTs) were identified from 1138 generated sequences, which fall into three categories, such as the toxin-like ESTs (531, 53.58%), the cellular component ESTs (255, 25.73%), and the no-match ESTs (205, 20.69%), as determined by gene function annotations. Of them, 190 non-redundant toxin-like peptides were identified and can be artificially grouped into 13 families based on their sequence homology and cysteine frameworks (families A-M). The predicted mature toxins contain 2-10 cysteines, which are predicted to form intramolecular disulfide bonds to stabilize their three-dimensional structures. Bioinformatics analysis showed that toxins from venom have high sequences variability and the biological targets for most toxins are unpredictable due to lack of homology to toxins with known functions in the database. Furthermore, RP-HPLC and MALDI-TOF analyses have identified a total of 110 different peptides physically existing in the venom, and many RP-HPLC fractions showed potent inhibitory activity on the heterologously expressed NaV1.7 channel. Most importantly, two novel NaV1.7 peptide antagonists, µ-Sparatoxin-Hp1 and µ-Sparatoxin-Hp2, were characterized. In conclusion, the present study has added many new members to the spider toxin superfamily and built the foundation for identifying novel modulators targeting ion channels in the venom.