Novel Bradykinin-Potentiating Peptides and Three-Finger Toxins from Viper Venom: Combined NGS Venom Gland Transcriptomics and Quantitative Venom Proteomics of the Azemiops feae Viper

Abstract

Feae’s viper Azemipos feae belongs to the Azemiopinae subfamily of the Viperidae family. The effects of Viperidae venoms are mostly coagulopathic with limited neurotoxicity manifested by phospholipases A2. From A. feae venom, we have earlier isolated azemiopsin, a novel neurotoxin inhibiting the nicotinic acetylcholine receptor. To characterize other A. feae toxins, we applied label-free quantitative proteomics, which revealed 120 unique proteins, the most abundant being serine proteinases and phospholipases A2. In total, toxins representing 14 families were identified, among which bradykinin-potentiating peptides with unique amino acid sequences possessed biological activity in vivo. The proteomic analysis revealed also basal (commonly known as non-conventional) three-finger toxins belonging to the group of those possessing neurotoxic activity. This is the first indication of the presence of three-finger neurotoxins in viper venom. In parallel, the transcriptomic analysis of venom gland performed by Illumina next-generation sequencing further revealed 206 putative venom transcripts. Together, the study unveiled the venom proteome and venom gland transciptome of A. feae, which in general resemble those of other snakes from the Viperidae family. However, new toxins not found earlier in viper venom and including three-finger toxins and unusual bradykinin-potentiating peptides were discovered.

De Novo Genome Assembly Highlights the Role of Lineage-Specific Gene Duplications in the Evolution of Venom in Fea's Viper (Azemiops feae)

“…Each of these PLA 2 genes had transcript per million values >42,000 inferred using StringTie ( supplementary table S3, Supplementary Material online). This is in contrast to previous work that identified several PLA 2 isoforms, only a few of which were thought to be expressed in the venom gland ( Tsai et al 2016 ; Babenko et al 2020 ). It is possible that differences in the number of PLA 2 genes identified between these studies and here could reflect gene copy number polymorphism within A. feae .…”

“…2 A ). Previous studies have found that PLA 2 s are the most dominant toxin in Azemiops venom gland transcriptomes, however, the frequencies of other toxin components differ between our study and published Azemiops venom gland transcriptomes ( Babenko et al 2020 ). Variation in venom composition within populations and between species is commonly documented in snakes ( Schenberg 1959 ; Glenn and Straight 1989 ); additional sampling and studies are necessary to fully understand the variation present in Azemiops venom composition as well as the molecular mechanisms underlying this variation.…”

Old World Vipers—A Review about Snake Venom Proteomics of Viperinae and Their Variations

“…This finding, as well as the nearly complete absence of svMP and the high abundance of 3FTx (15%) is uncommon within venoms of this genus [ 77 ]. Even 3FTx have been extensively characterized from Elapidae, only few are described for Viperinae, like D. russelii and V. nikolskii , and the occurrence in such high amounts is considered as atypical and a rare toxin family in viper venoms [ 190 , 209 , 210 , 211 , 212 , 213 ].…”

Cardiovascular Effects of Snake Toxins: Cardiotoxicity and Cardioprotection

“…The BPPs R-BPP and Y-BPP, which we uncovered in the venom of the viper Azemiops feae ( Fig. 1 ) [ 26 ], are more similar to peptides exhibiting specificity for the ACE C domain and may be considered as a basis for the development of C domain-selective drugs, which would differ structurally from captopril.…”