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Tan CH, Tan KY, Ng TS, Tan NH, Chong HP. De Novo Venom Gland Transcriptome Assembly and Characterization for Calloselasma rhodostoma (Kuhl, 1824), the Malayan Pit Viper from Malaysia: Unravelling Toxin Gene Diversity in a Medically Important Basal Crotaline. Toxins (Basel) 2023; 15:toxins15050315. [PMID: 37235350 DOI: 10.3390/toxins15050315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 04/24/2023] [Accepted: 04/26/2023] [Indexed: 05/28/2023] Open
Abstract
In Southeast Asia, the Malayan Pit Viper (Calloselasma rhodostoma) is a venomous snake species of medical importance and bioprospecting potential. To unveil the diversity of its toxin genes, this study de novo assembled and analyzed the venom gland transcriptome of C. rhodostoma from Malaysia. The expression of toxin genes dominates the gland transcriptome by 53.78% of total transcript abundance (based on overall FPKM, Fragments Per Kilobase Million), in which 92 non-redundant transcripts belonging to 16 toxin families were identified. Snake venom metalloproteinase (SVMP, PI > PII > PIII) is the most dominant family (37.84% of all toxin FPKM), followed by phospholipase A2 (29.02%), bradykinin/angiotensin-converting enzyme inhibitor-C-type natriuretic peptide (16.30%), C-type lectin (CTL, 10.01%), snake venom serine protease (SVSP, 2.81%), L-amino acid oxidase (2.25%), and others (1.78%). The expressions of SVMP, CTL, and SVSP correlate with hemorrhagic, anti-platelet, and coagulopathic effects in envenoming. The SVMP metalloproteinase domains encode hemorrhagins (kistomin and rhodostoxin), while disintegrin (rhodostomin from P-II) acts by inhibiting platelet aggregation. CTL gene homologues uncovered include rhodocytin (platelet aggregators) and rhodocetin (platelet inhibitors), which contribute to thrombocytopenia and platelet dysfunction. The major SVSP is a thrombin-like enzyme (an ancrod homolog) responsible for defibrination in consumptive coagulopathy. The findings provide insight into the venom complexity of C. rhodostoma and the pathophysiology of envenoming.
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Affiliation(s)
- Choo Hock Tan
- Department of Pharmacology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Kae Yi Tan
- Department of Molecular Medicine, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Tzu Shan Ng
- Department of Molecular Medicine, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Nget Hong Tan
- Department of Molecular Medicine, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
| | - Ho Phin Chong
- Department of Pharmacology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Malaysia
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Liu CC, Wu CJ, Hsiao YC, Yang YH, Liu KL, Huang GJ, Hsieh CH, Chen CK, Liaw GW. Snake venom proteome of Protobothrops mucrosquamatus in Taiwan: Delaying venom-induced lethality in a rodent model by inhibition of phospholipase A 2 activity with varespladib. J Proteomics 2020; 234:104084. [PMID: 33359941 DOI: 10.1016/j.jprot.2020.104084] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 12/01/2020] [Accepted: 12/20/2020] [Indexed: 12/26/2022]
Abstract
Protobothrops mucrosquamatus, also known as the brown spotted pit viper or Taiwanese habu, is a medically significant venomous snake in Taiwan, especially in the northern area. To more fully understand the proteome profile of P. mucrosquamatus, we characterized its venom composition using a bottom-up proteomic approach. Whole venom components were fractionated by RP-HPLC and then analyzed by SDS-PAGE. Each protein band in gels was excised and subjected to protein identification by LC-MS/MS. A subsequent proteomic analysis revealed the presence of 61 distinct proteins belonging to 19 families in P. mucrosquamatus venom. Snake venom metalloproteinase (SVMP; 29.4%), C-type lectin (CLEC; 21.1%), snake venom serine protease (SVSP; 17.6%) and phospholipase A2 (PLA2; 15.9%) were the most abundant protein families, whereas several low-abundance proteins, categorized into eight protein families, were demonstrated in P. mucrosquamatus venom for the first time. Because PLA2 is known to make a major contribution to venom lethality, we evaluated whether the known PLA2 inhibitor, varespladib, was capable of preventing the toxic effects of P. mucrosquamatus venom. This small-molecule drug demonstrated the ability to inhibit PLA2 activity in vitro (IC50 = 101.3 nM). It also blunted lethality in vivo, prolonging survival following venom injection in a mouse model, but it showed limited potency against venom-induced local hemorrhage in this model. Our findings provide essential biological and pathophysiological insights into the composition of P. mucrosquamatus venom and suggest PLA2 inhibition as an adjunctive or alternative therapeutic strategy in the clinical management of P. mucrosquamatus envenoming in emergency medicine. SIGNIFICANCE: P. mucrosquamatus envenomation is a significant medical concern in Taiwan, especially in the northern region. Although antivenom is commonly used for rescuing P. mucrosquamatus envenoming, severe clinical events still occur, with more than 20% of cases requiring surgical intervention. Small-molecule therapy offers several advantages as a potential adjunctive, or even alternative, to antivenom treatment, such as heat stability, low antigenicity and ease of administration, among others. A deeper understanding of the venom proteome of P. mucrosquamatus would aid in the discovery of small-molecule drugs that could be repurposed to target specific venom proteins. Here, we applied a bottom-up proteomic approach to characterize the protein profile of P. mucrosquamatus venom. Varespladib, a small-molecule drug used to treat inflammatory disease, was repurposed to inhibit the toxicity of P. mucrosquamatus venom, and was shown to reduce the lethal effects of P. mucrosquamatus envenomation in a rodent model. Varespladib might be used as a first-aid therapeutic against P. mucrosquamatus envenoming in the pre-referral period and/or as an adjunctive agent administered together with anti-P. mucrosquamatus antivenom.
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Affiliation(s)
- Chien-Chun Liu
- Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan
| | - Cho-Ju Wu
- Department of Emergency Medicine, Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan
| | - Yung-Chin Hsiao
- Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan; Liver Research Center, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan
| | - Ya-Han Yang
- School of Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Kuei-Lin Liu
- Faculty of Biotechnology and Laboratory Science in Medicine, School of Medical Technology and Engineering, National Yang-Ming University, Taipei, Taiwan
| | - Guo-Jen Huang
- Department and Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Cheng-Hsien Hsieh
- Department of Emergency Medicine, En Chu Kong Hospital, New Taipei City, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chun-Kuei Chen
- Department of Emergency Medicine, Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan.
| | - Geng-Wang Liaw
- Department of Emergency Medicine, Yeezen General Hospital, Taoyuan, Taiwan.
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Abstract
p67 is a type I transmembrane glycoprotein of the terminal lysosome of African trypanosomes. Its biosynthesis involves transport of an initial gp100 ER precursor to the lysosome, followed by cleavage to N-terminal (gp32) and C-terminal (gp42) subunits that remain non-covalently associated. p67 knockdown is lethal, but the only overt phenotype is an enlarged lysosome (~250 to >1000 nm). Orthologues have been characterized in Dictyostelium and mammals. These have processing pathways similar to p67, and are thought to have phospholipase B-like (PLBL) activity. The mouse PLBD2 crystal structure revealed that the PLBLs represent a subgroup of the larger N-terminal nucleophile (NTN) superfamily, all of which are hydrolases. NTNs activate by internal autocleavage mediated by a nucleophilic residue, i.e. Cys, Ser or Thr, on the upstream peptide bond to form N-terminal α (gp32) and C-terminal β (gp42) subunits that remain non-covalently associated. The N-terminal residue of the β subunit is then catalytic in subsequent hydrolysis reactions. All PLBLs have a conserved Cys/Ser dipeptide at the α/β junction (Cys241/Ser242 in p67), mutation of which renders p67 non-functional in RNAi rescue assays. p67 orthologues are found in many clades of parasitic protozoa, thus p67 is the founding member of a group of hydrolases that likely play a role broadly in the pathogenesis of parasitic infections.
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