Purification and amino-acid sequence of a nerve growth factor from the venom of Vipera russelli russelli

Transcriptomic and functional proteomics analyses to unveil the common and unique pathway(s) of neuritogenesis induced by Russell's viper venom nerve growth factor in rat pheochromocytoma neuronal cells

Background: The snake venom nerve growth factor (NGF)-induced signal transduction mechanism has never been explored.Research design and methods: Homology modeling and molecular dynamic studies of the interaction between Russell's viper venom NGF (RVV-NGFa) and mammalian tropomyosin-receptor kinase A (TrkA) was done by computational analysis. Transcriptomic and quantitative tandem mass spectrometry analyses determined the expression of intracellular genes and proteins, respectively, in RVV-NGFa-treated PC-12 neuronal cells. Small synthetic inhibitors of the signal transduction pathways were used to validate the major signaling cascades of neuritogenesis by RVV-NGFa.Results: A comparative computational analysis predicted the binding of RVV-NGFa, mouse 2.5S-NGF (conventional neurotrophin), and Nn-α-elapitoxin-1 (non-conventional neurotrophin) to different domains of the TrkA receptor in PC-12 cells. The transcriptomic and quantitative proteomic analyses in unison showed differential expressions of common and unique genes and intracellular proteins, respectively, in RVV-NGFa-treated cells compared to control (untreated) mouse 2.5S-NGF and Nn-α-elapitoxin-1-treated PC-12 cells. The RVV-NGFa primarily triggered the mitogen-activated protein kinase-1 (MAPK1) signaling pathway for inducing neuritogenesis; however, 36 pathways of neuritogenesis were uniquely expressed in RVV-NGFa-treated PC-12 cells compared to mouse 2.5S NGF or Nn-α-elapitoxin-1 treated cells.Conclusion: The common and unique intracellular signaling pathways of neuritogenesis by classical and non-classical neurotrophins were identified.

Molecular evolution of vertebrate neurotrophins: co-option of the highly conserved nerve growth factor gene into the advanced snake venom arsenalf

Neurotrophins are a diverse class of structurally related proteins, essential for neuronal development, survival, plasticity and regeneration. They are characterized by major family members, such as the nerve growth factors (NGF), brain-derived neurotrophic factors (BDNF) and neurotrophin-3 (NT-3), which have been demonstrated here to lack coding sequence variations and follow the regime of negative selection, highlighting their extremely important conserved role in vertebrate homeostasis. However, in stark contrast, venom NGF secreted as part of the chemical arsenal of the venomous advanced snake family Elapidae (and to a lesser extent Viperidae) have characteristics consistent with the typical accelerated molecular evolution of venom components. This includes a rapid rate of diversification under the significant influence of positive-selection, with the majority of positively-selected sites found in the secreted β-polypeptide chain (74%) and on the molecular surface of the protein (92%), while the core structural and functional residues remain highly constrained. Such focal mutagenesis generates active residues on the toxin molecular surface, which are capable of interacting with novel biological targets in prey to induce a myriad of pharmacological effects. We propose that caenophidian NGFs could participate in prey-envenoming by causing a massive release of chemical mediators from mast cells to mount inflammatory reactions and increase vascular permeability, thereby aiding the spread of other toxins and/or by acting as proapoptotic factors. Despite their presence in reptilian venom having been known for over 60 years, this is the first evidence that venom-secreted NGF follows the molecular evolutionary pattern of other venom components, and thus likely participates in prey-envenomation.

Transient signaling of Erk1/2, Akt and PLCgamma induced by nerve growth factor in brain capillary endothelial cells

Cumulative evidences suggest that nerve growth factor (NGF) promotes angiogenic effects such as proliferation and migration of endothelial cells (ECs) from different vascular beds, induces capillary sprouting in chorioallantoic membrane and improves in vivo vascularization in a hind-limb ischemic model. In the present study, we sought to investigate the signaling properties of NGF in a microcapillary ECs model compared to those of a neuronal model. NGF-induced phosphorylation of signaling molecules Erk1/2, Akt and PLCgamma were measured using Western blotting and compared between mouse NGF (mNGF) and snake venom NGF analogues. NGFs-induced signaling was TrkA mediated as evident by inhibition with the TrkA antagonist K252a. NGF and its analogues-induced signaling in ECs were characterized by a transient effect in contrast to a prolonged stimulation in neuronal cells. The potency of mouse, cobra and viper NGFs to induce Erk1/2 phosphorylation in ECs was higher than in neurons. In ECs, mNGF exhibited the highest efficacy of stimulation of Erk1/2 phosphorylation, followed by viper and cobra NGFs. The efficacy of stimulation of Erk1/2 phosphorylation measured with neurons was opposite from that in ECs. NGF-induced temporal signaling differences between ECs and neurons may explain the dual vascular and neurotrophic effects of this growth factor.

Nerve growth factor from Vipera lebetina venom

Nerve growth factor was isolated from the Vipera lebetina venom by a four-step procedure including gel filtration, ion exchange, heparin and hydrophobic chromatography. The purified protein is a glycosylated non-covalently bound homodimer with monomeric molecular mass of 14,380 Da. The cDNA encoding NGF is cloned and sequenced. The amino acid sequence translated from the cDNA comprises 117 or 119 amino acids depending on the N-terminus (truncated or not). The recombinant NGF (expressed in Escherichia coli) was used to prepare the anti-NGF antiserum. The antiserum interacted with the wild-type NGF and enabled to localize NGF during the purification procedure in parallel with MALDI-TOF analysis of tryptic peptides. The isolated NGF caused neurite outgrowth from PC12 cells in concentrations beginning from 2.5 ng/ml.

Post-translational modification accounts for the presence of varied forms of nerve growth factor in Australian elapid snake venoms

The Australian elapid snakes are amongst the most venomous snakes in the world, but much less is known about the overall venom composition in comparison to Asian and American snakes. We have used a combined approach of cDNA cloning and 2-DE with MS to identify nerve growth factor (NGF) in venoms of the Australian elapid snakes and demonstrate its neurite outgrowth activity. While a single 730 nucleotide ORF, coding for a 243 amino acid precursor protein was detected in all snakes, use of 2-DE identified NGF proteins with considerable variation in molecular size within and between the different snakes. The variation in size can be explained at least in part by N-linked glycosylation. It is possible that these modifications alter the stability, activity and other characteristics of the snake NGFs. Further characterisation is necessary to delineate the function of the individual NGF isoforms.

Two-step chromatographic method for separation and purification of nerve growth factor from venom of Chinese cobra

By selecting the different combination schemes, a simple, fast and highly efficient method for separation and purification of nerve growth factor (NGF) from venom of Chinese cobra is reported in this paper. This purification process consists of a two-step chromatographic separation on DEAE-Sepharose F.F. anion-exchange medium followed by a Sephadex G-50 gel filtration. On reducing and non-reducing sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), the nerve growth factor obtained with this process proved to be homogeneous and its molecular weight was separately estimated to be approximately 14.5 and 29.0kD, which was consistent with that reported in literature; and on high performance size-exclusion chromatography and reversed-phase chromatography, its purity was about 99%. The yield of this purification method was 0.51% and the nerve growth factor obtained had the activity of eliciting neurite outgrowth from chick embryonic dorsal root ganglia. The optimum concentration of nerve growth factor was 5-100ng/ml and the minimal concentration eliciting neurite outgrowth from chick embryonic dorsal root ganglia was 5.0 ng/ml.

Analysis of Lectin-Bound Glycoproteins in Snake Venom from the Elapidae and Viperidae Families

This paper describes an efficient method of studying the glycoproteins found in snake venom. The glycosylation profiles of the Elapidae and Viperidae snake families were analyzed using FITC-labeled lectin glycoconjugates. The Con A-agarose affinity enrichment technique was used to fractionate glycoproteins from the N. naja kaouthia venom. The results revealed a large number of Con A binding glycoproteins, most of which have moderate to high molecular weights. To identify the proteins, the isolated glycoprotein fractions were subjected to two-dimensional electrophoresis and MALDI-TOF MS. Protein sequences were compared with published protein databases to determine for their biological functions.

Characterization of nerve growth factors (NGFs) from snake venoms by use of a novel, quantitative bioassay utilizing pheochromocytoma (PC12) cells overexpressing human trkA receptors

Snake venoms are a very abundant source of nerve growth factors (NGF). NGFs of Elapidae showing 65% sequence homology with mouse or human NGF, while the Viperidae NGF shows N-glycosylation (Asn-21) typical of these mammalian NGFs. Snake NGF-induced neurite outgrowth (neurotropic activity) was measured in the past by using PC12 cell or dorsal root ganglion bioassays. The present study was aimed at comparing, by dose-response experiments, the neurotropic activity of cobra and vipera versus mammalian NGFs, by using a novel bioassay involving PC12 cells genetically engineered to overexpress NGF-trkA receptors of human origin. These cells respond to NGF by differentiation (morphologically expressed as neurite outgrowth) by a process mediated by NGF-trkA receptors. This process was evaluated by two different criteria: (1) elongation of neurites (E), and (2) Percentage of responsive cells (PRC) determined by digital acquisition of data and computer analysis. We found that snake venom NGFs were less potent than mouse NGF, and that cobra NGF was more potent than vipera NGF. These data indicate the following order of NGF activity towards recombinant human trkA receptors: recombinant human NGF>mouse NGF>cobra NGF>vipera NGF. The neurotropic efficacy of these NGFs was found to be similar, reaching 80-90% of maximal activity obtained with all NGF forms. Interestingly, cobra (but not vipera) NGF demonstrated prolonged neurotropic activity compared with mouse NGF. The results of the present study indicate that cobra and vipera venom NGFs represent natural agonists of human trkA-receptor of a lower potency, but of similar efficacy, compared with mammalian NGFs. These compounds are important pharmacological tools to characterize the trkA receptor structure-function relationship, and to develop novel neurotropic drugs.

cDNA sequence and molecular modeling of a nerve growth factor from Bothrops jararacussu venomous gland

The complete nucleotide sequence of a nerve growth factor precursor from Bothrops jararacussu snake (Bj-NGF) was determined by DNA sequencing of a clone from cDNA library prepared from the poly(A) + RNA of the venom gland of B. jararacussu. cDNA encoding Bj-NGF precursor contained 723 bp in length, which encoded a prepro-NGF molecule with 241 amino acid residues. The mature Bj-NGF molecule was composed of 118 amino acid residues with theoretical pI and molecular weight of 8.31 and 13,537, respectively. Its amino acid sequence showed 97%, 96%, 93%, 86%, 78%, 74%, 76%, 76% and 55% sequential similarities with NGFs from Crotalus durissus terrificus, Agkistrodon halys pallas, Daboia (Vipera) russelli russelli, Bungarus multicinctus, Naja sp., mouse, human, bovine and cat, respectively. Phylogenetic analyses based on the amino acid sequences of 15 NGFs separate the Elapidae family (Naja and Bungarus) from those Crotalidae snakes (Bothrops, Crotalus and Agkistrodon). The three-dimensional structure of mature Bj-NGF was modeled based on the crystal structure of the human NGF. The model reveals that the core of NGF, formed by a pair of beta-sheets, is highly conserved and the major mutations are both at the three beta-hairpin loops and at the reverse turn.

A nerve growth factor from the venom of Chinese cobra (Naja naja atra) and its effects on male reproductive system in rats

A nerve growth factor (NGF) was isolated from the venom of Chinese cobra (Naja naja atra) by ion exchange chromatography, gel filtration and fast protein liquid chromatography (FPLC). The N-terminal sequence of 22 amino acid residues was identical with other NGFs previously purified from the venom of the same genus. The NGF monomer molecular weight was estimated to be 13,500 by reducing SDS-PAGE and the isoelectric point was determined to be 7.2 by isoelectric focusing electrophoresis. NGF improved the epididymal sperm motility of male rats and increased the pregnancy rate and fetus number of mated female rats. The serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) of male rats administrated NGF + gossypol was lower than that of male rats administrated gossypol. Histological sections of testes and epididymides showed that NGF reduced the destructive effects of gossypol on rat testes.

Cloning of a cDNA encoding a nerve growth factor precursor from the Agkistrodon halys Pallas

Based on the high conservation in the 5' and 3' untranslated regions of NGF cDNAs, oligonucleotides complementary to all these known sequences were synthesized. By RT-PCR, we successfully isolated the complementary DNA encoding NGF precursor from the Agkistrodon halys Pallas (a Chinese snake strain). The nucleotide sequence which presents 90.5%, 88.6% and 63.4% homology to that of Krait Bungarus multicinctus, cobra and human NGF respectively, encoded a prepro-NGF molecule with 241 amino acids and a mature NGF molecule with 119 amino acids. The NGF cDNA inserts were subcloned into pCDNA3 expression vector and then transfected into COS-7 cells. The supernatant of the transfected cells turned out NGF biological activity as assayed by the survival rate of PC12 pheochromocytoma cells.

The affinity technology in downstream processing

The quality criteria imposed on several biochemicals are stringent, thus, high-separation purification technology is important to downstream processing. Affinity-based purification technologies are regarded as the finest available, and each one differs in its purifying ability, economy, processing speed and capacity. The most widely used affinity technology is classical affinity chromatography, however, other chromatography-based approaches have also been developed, for example, perfusion affinity chromatography, hyperdiffusion affinity chromatography, high-performance affinity chromatography, centrifugal affinity chromatography, affinity repulsion chromatography, heterobifunctional ligand affinity chromatography and the various chromatographic applications of 'affinity tails'. On the other hand, non-chromatographic affinity technologies aim at high throughput and seek to circumvent problems associated with diffusion limitations experienced with most chromatographic packings. Continuous affinity recycle extraction, aqueous two-phase affinity partitioning, membrane affinity filtration, affinity cross-flow ultrafiltration, reversible soluble affinity polymer separation and affinity precipitation are all non-chromatographic technologies. Several types of affinity ligands are used to different extents; antibodies and their fragments, receptors and their binding substances, avidin/biotin systems, textile and biomimetic dyes, (oligo)peptides, antisense peptides, chelated metal cations, lectins and phenylboronates, protein A and G, calmodulin, DNA, sequence-specific DNA, (oligo)nucleotides and heparin. Likewise, there are several support types developed and used; natural, synthetic, inorganic and composite materials.