Balsamin, a novel ribosome-inactivating protein from the seeds of Balsam apple Momordica balsamina

High-quality Momordica balsamina genome elucidates its potential use in improving stress resilience and therapeutic properties of bitter gourd

Introduction

Momordica balsamina is the closest wild species that can be crossed with an important fruit vegetable crop, Momordica charantia, has immense medicinal value, and placed under II subclass of primary gene pool of bitter gourd. M. balsamina is tolerant to major biotic and abiotic stresses. Genome characterization of Momordica balsamina as a wild relative of bitter gourd will contribute to the knowledge of the gene pool available for improvement in bitter gourd. There is potential to transfer gene/s related to biotic resistance and medicinal importance from M. balsamina to M. charantia to produce high-quality, better yielding and stress tolerant bitter gourd genotypes.

Methods

The present study provides the first and high-quality chromosome-level genome assembly of M. balsamina with size 384.90 Mb and N50 30.96 Mb using sequence data from 10x Genomics, Nanopore, and Hi-C platforms.

Results

A total of 6,32,098 transposons elements; 2,15,379 simple sequence repeats; 5,67,483 transcription factor binding sites; 3,376 noncoding RNA genes; and 41,652 protein-coding genes were identified, and 4,347 disease resistance, 67 heat stress-related, 05 carotenoid-related, 15 salt stress-related, 229 cucurbitacin-related, 19 terpenes-related, 37 antioxidant activity, and 06 sex determination-related genes were characterized.

Conclusion

Genome sequencing of M. balsamina will facilitate interspecific introgression of desirable traits. This information is cataloged in the form of webgenomic resource available at http://webtom.cabgrid.res.in/mbger/. Our finding of comparative genome analysis will be useful to get insights into the patterns and processes associated with genome evolution and to uncover functional regions of cucurbit genomes.

Recent advances of bioactive proteins/polypeptides in the treatment of breast cancer

Proteins do not only serve as nutrients to fulfill the demand for food, but also are used as a source of bioactive proteins/polypeptides for regulating physical functions and promoting physical health. Female breast cancer has the highest incidence in the world and is a serious threat to women's health. Bioactive proteins/polypeptides exert strong anti-tumor effects and exhibit inhibition of multiple breast cancer cells. This review discussed the suppressing effects of bioactive proteins/polypeptides on breast cancer in vitro and in vivo, and their mechanisms of migration and invasion inhibition, apoptosis induction, and cell cycle arrest. This may contribute to providing a basis for the development of bioactive proteins/polypeptides for the treatment of breast cancer.

Graphical abstract

Identification of a Novel Anti-HIV-1 Protein from Momordica balsamina Leaf Extract

Our lab investigates the anti-HIV-1 activity in Momordica balsamina (M. balsamina) leaf extract. Traditional Senegalese healers have used M. balsamina leaf extract as a part of a plant-based treatment for HIV/AIDS infections. Our overall goal is to define and validate the scientific basis for using M. balsamina leaf extract as a part of the traditional Senegalese treatment. As an initial characterization of this extract, we used activity-guided fractionation to determine the active ingredient's solubility and relative size. We found that M. balsamina leaf extract inhibits HIV-1 infection by >50% at concentrations of 0.02 mg/mL and above and is not toxic over its inhibitory range (0-0.5 mg/mL). We observed significantly more antiviral activity in direct water and acetonitrile extractions (p ≤ 0.05). We also observed significantly more antiviral activity in the aqueous phases of ethyl acetate, chloroform, and diethyl ether extractions (p ≤ 0.05). Though most of the antiviral activity partitioned into the aqueous layers, some antiviral activity was present in the organic layers. We show that the active agent in the plant extracts is at least 30 kD in size. Significantly more antiviral activity was retained in 3, 10, and 30 kD molecular weight cutoff filters (p ≤ 0.05). In contrast, most of the antiviral activity passed through the 100 kD filter (p ≤ 0.05). Because the active anti-HIV-1 agent presented as a large, amphiphilic molecule we ran the purified extract on an SDS-page gel. We show that the anti-HIV-1 activity in the leaf extracts is attributed to a 30 kDa protein we call MoMo30. This article describes how MoMo30 was determined to be responsible for its anti-HIV-1 activity.

Effect of the combination of Leptadenia hastata (pers) decne and Momordica balsamina linn leaf extracts on lipid profile of streptozotocin-induced diabetic rats

Background

Changes in blood lipid level (dyslipidemia) play a central role in the onset and pathogenesis of macrovascular complications of diabetes mellitus. Traditional herbal healers commonly use anti-diabetic polyherbal formulations to provide a multi-therapeutic approach for the treatment of diabetes mellitus and its associated complications. The effect of the aqueous leaf extracts of Leptadenia hastata (pers) Decne, Momordica balsamina Linn and their combination on lipid profile of streptozotocin (STZ)-induced diabetic rats was therefore evaluated in the present study.

Results

We evaluated the serum lipid profile and blood glucose level of STZ-induced diabetic rats (60 mg/kg body weight) treated with the aqueous leaf extracts of L. hastata (400 mg/kg) and M. balsamina (200 mg/kg) alone and in combination (400 + 200 mg/kg) after a period of 4 weeks. A significantly decreased (p < 0.05) level of total cholesterol (TC), triglyceride (TG), very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterol levels and increased (p < 0.05) level of high-density lipoprotein (HDL) cholesterol was observed in all the treated groups when compared to the untreated diabetic rats. Furthermore, the combination treatment was potentially a more effective blood lipid-lowering (p < 0.05) agent when compared to the single treatments.

Conclusion

Results from this study demonstrated the blood lipid-lowering potential of the aqueous leaf extracts of L. hastata, M. balsamina, and their combination. However, the polyherbal combination could be more potent in controlling diabetes mellitus, associated dyslipidemia, and its complications.

Therapeutic Potential of Medicinal Plant Proteins: Present Status and Future Perspectives

Biologically active molecules obtained from plant sources, mostly including secondary metabolites, have been considered to be of immense value with respect to the treatment of various human diseases. However, some inevitable limitations associated with these secondary metabolites like high cytotoxicity, low bioavailability, poor absorption, low abundance, improper metabolism, etc., have forced the scientific community to explore medicinal plants for alternate biologically active molecules. In this context, therapeutically active proteins/peptides from medicinal plants have been promoted as a promising therapeutic intervention for various human diseases. A large number of proteins isolated from the medicinal plants have been shown to exhibit anti-microbial, anti-oxidant, anti-HIV, anticancerous, ribosome-inactivating and neuro-modulatory activities. Moreover, with advanced technological developments in the medicinal plant research, medicinal plant proteins such as Bowman-Birk protease inhibitor and Mistletoe Lectin-I are presently under clinical trials against prostate cancer, oral carcinomas and malignant melanoma. Despite these developments and proteins being potential drug candidates, to date, not a single systematic review article has documented the therapeutical potential of the available biologically active medicinal plant proteome. The present article was therefore designed to describe the current status of the therapeutically active medicinal plant proteins/peptides vis-à-vis their potential as future protein-based drugs for various human diseases. Future insights in this direction have also been highlighted.

Combination of Balsamin and Flavonoids Induce Apoptotic Effects in Liver and Breast Cancer Cells

Flavonoids such as naringenin, quercetin, and naringin are known to exhibit anticancer properties. In this study, we examined the effects of these flavonoids on cell viability and apoptotic pathways of cancer cells, either singly or in combination with the type 1 ribosome inactivating protein, Balsamin. Treatment with flavonoids (naringenin, quercetin, and naringin) plus Balsamin for 48 h reduced HepG2 and MCF-7 cell viability, increased the activation of caspase-3 and -8, and induced apoptosis through up-regulation of pro-apoptotic genes and down-regulation of anti-apoptotic genes. Out of the three flavonoids tested, the Balsamin-Naringenin and Balsamin-Quercetin combinations appeared to be most effective compared to the Balsamin-Naringin combination. Balsamin combined with flavonoids also activated endoplasmic reticulum (ER)-stress–mediated apoptosis in breast cancer (MCF-7) cells, which was not activated by Balsamin treatment alone. These experimental results showed that Balsamin combined with flavonoids can reduce HepG2 and MCF-7 cells viability and induce apoptosis, which could be considered as a promising therapeutic approach to sensitize cells to Balsamin treatment, thereby improving its efficacy in breast or liver cancer therapy.

Purification and functional characterization of recombinant balsamin, a ribosome-inactivating protein from Momordica balsamina

Balsamin, a type I ribosome-inactivating protein (RIP), has been shown to inhibit HIV-1 replication at the translation step. Our recent studies have shown that balsamin also possess anti-tumor, antibacterial and DNase-like activity, however, the amount of natural balsamin in Momordica balsamina seeds is limited and preclinical studies require large quantities of pure, bioactive balsamin. Therefore, in this study, we cloned the balsamin gene, expressed it in E.coli BL21 (DE3) strain and purified it by nickel affinity chromatography. Functional analysis indicated that balsamin exhibits both RNA N-glycosidase activity, releasing the Endo-fragment from rabbit reticulocyte rRNA, and DNase-like activity, converting the supercoiled form of a plasmid into the linear form in a concentration-dependent manner. Analysis of secondary structure revealed that recombinant balsamin mainly consisted of α-helical and random coiled with minimal turns and β-sheets. Recombinant balsamin was found to be stable in the temperature range of 20-60 °C and pH range of 6-9. Antimicrobial assays showed that the minimum inhibitory concentrations of recombinant balsamin for various pathogens ranged between 1.56 and 12.5 μg/ml. Heterologous expression and purification of balsamin carries great importance as it provides an alternative approach for large-scale preparation of biologically active recombinant balsamin, which is difficult from its natural source.

The Plant Ribosome-Inactivating Proteins Play Important Roles in Defense against Pathogens and Insect Pest Attacks

Ribosome-inactivating proteins (RIPs) are toxic N-glycosidases that depurinate eukaryotic and prokaryotic rRNAs, thereby arresting protein synthesis during translation. RIPs are widely found in various plant species and within different tissues. It is demonstrated in vitro and in transgenic plants that RIPs have been connected to defense by antifungal, antibacterial, antiviral, and insecticidal activities. However, the mechanism of these effects is still not completely clear. There are a number of reviews of RIPs. However, there are no reviews on the biological functions of RIPs in defense against pathogens and insect pests. Therefore, in this report, we focused on the effect of RIPs from plants in defense against pathogens and insect pest attacks. First, we summarize the three different types of RIPs based on their physical properties. RIPs are generally distributed in plants. Then, we discuss the distribution of RIPs that are found in various plant species and in fungi, bacteria, algae, and animals. Various RIPs have shown unique bioactive properties including antibacterial, antifungal, antiviral, and insecticidal activity. Finally, we divided the discussion into the biological roles of RIPs in defense against bacteria, fungi, viruses, and insects. This review is focused on the role of plant RIPs in defense against bacteria, fungi, viruses, and insect attacks. The role of plant RIPs in defense against pathogens and insects is being comprehended currently. Future study utilizing transgenic technology approaches to study the mechanisms of RIPs will undoubtedly generate a better comprehending of the role of plant RIPs in defense against pathogens and insects. Discovering additional crosstalk mechanisms between RIPs and phytohormones or reactive oxygen species (ROS) against pathogen and insect infections will be a significant subject in the field of biotic stress study. These studies are helpful in revealing significance of genetic control that can be beneficial to engineer crops tolerance to biotic stress.

Curcin C, a novel type I ribosome-inactivating protein from the post-germinating cotyledons of Jatropha curcas

A novel type I ribosome-inactivating protein (RIP), designated as curcin C, was purified from Jatropha curcas, an important feedback source of bio-fuel. Molecular mass and isoelectric point of curcin C were 31.398 kDa and 7.12 as detected by MALTI-TOF assay and capillary electrophoresis assay, respectively. N-terminal sequence and LC-MS/MS analyses confirmed that curcin C is a type I RIP having high homology, but not the exactly the same with curcin, another type 1 RIP isolated from the endosperm of J. curcas. It exhibited N-glycosidase activity and in vitro translation inhibition activity. Moreover, curcin C displayed a strong selectively anti-tumor activity on human cancer cells. Its cytotoxicity against osteosarcoma cell line U20S is even higher than that of Paclitaxel with IC₅₀ of 0.019 μM. Purification and identification of curcin C not only suggested its potential in natural anticancer drug development, but also provide chance to understanding different cytotoxic action among different RIPs.

Balsamin induces apoptosis in breast cancer cells via DNA fragmentation and cell cycle arrest

Breast cancer is the second most common cancer causing death worldwide with metastasis and disease relapse being the major drawbacks in current treatments. Therefore, development of novel drugs is needed. Balsamin, a 28 kDa Type I ribosome-inactivating protein, is rich in the seeds of Momordica balsamina. In this study, the molecular mechanism and the possible effects of balsamin on the two key hallmarks of cancer were investigated. Firstly, the induction of apoptosis in human breast cancer MCF-7 and BT549 cells showed that balsamin-induced apoptosis involved increases in caspase-3 and caspase-8 activity, upregulation of Bax, Bid, and Bad, and downregulation of BCL-2 and BCL-XL. Furthermore, balsamin inhibited the proliferation of breast cancer cells in a dose-dependent manner with IC₅₀ values of 24.53 and 32.79 µg/ml for MCF-7 and BT549 cells, respectively. Moreover, flow cytometric analysis revealed that balsamin induced S-/G-phase cell cycle arrest. Our studies show that balsamin has anti-tumor activity and could be used as a neutraceutical for the treatment of breast cancer.

The Roles of Alpha-Momorcharin and Jasmonic Acid in Modulating the Response of Momordica charantia to Cucumber Mosaic Virus

Alpha-momorcharin (α-MMC) is a type-I ribosome inactivating protein with a molecular weight of 29 kDa that is found in Momordica charantia, and has been shown to be effective against a broad range of human viruses as well as having anti-tumor activities. However, the role of endogenous α-MMC under viral infection and the mechanism of the anti-viral activities of α-MMC in plants are still unknown. To study the effect of α-MMC on plant viral defense and how α-MMC increases plant resistance to virus, the M. charantia–cucumber mosaic virus (CMV) interaction system was investigated. The results showed that the α-MMC level was positively correlated with the resistance of M. charantia to CMV. α-MMC treatment could alleviate photosystem damage and enhance the ratio of glutathione/glutathione disulfide in M. charantia under CMV infection. The relationship of α-MMC and defense related phytohormones, and their roles in plant defense were further investigated. α-MMC treatment led to a significant increase of jasmonic acid (JA) and vice versa, while there was no obvious relevance between salicylic acid and α-MMC. In addition, reactive oxygen species (ROS) were induced in α-MMC-pretreated plants, in a similar way to the ROS burst in JA-pretreated plants. The production of ROS in both ibuprofen (JA inhibitor) and (α-MMC+ibuprofen)-pretreated plants was reduced markedly, leading to a greater susceptibility of M. charantia to CMV. Our results indicate that the anti-viral activities of α-MMC in M. charantia may be accomplished through the JA related signaling pathway.

Isolation and partial characterization of 3 nontoxic d-galactose-specific isolectins from seeds of Momordica balsamina

Three isolectins denoted hereforth MBaL-30, MBaL-60, and MBaL-80 were isolated from seeds extract of Momordica balsamina by 30%, 60%, and 80% ammonium sulfate saturations, respectively. The native molecular weights of these lectins, as judged by gel filtration, were 108, 56, and 160 kDa, respectively. On SDS-PAGE, under reduced condition, 27 kDa band was obtained for all isolectins. The lectins hemagglutinating activities were variably inhibited by d-galactose (minimum inhibitory concentrations = 12.5mM, 50mM, and 0.391mM, respectively). MBaL-30 and -60 could agglutinate all human blood types with slight preference for the A and O blood groups, whereas MBaL-80 did not agglutinate B and AB blood types. The 3 isolectins were purified from crude seeds extract, collectively, in a single step on the affinity matrix Lactamyl-Seralose 4B; this purified lectin fraction, which contains all isolectins, is termed MBaL. The N-terminal of MBaL till the 25th amino acid was NLSLSELDFSADTYKSFIKNLRKQL, which shares 88% sequence identity with Momordica charantia lectin type-2 ribosomal inactivating protein from Momordica charantia and 50% with momordin II from Momordica balsamina. MBaL retained 100% activity at up to 50°C for 30 minutes. MBaL-30 and MBaL-60 exhibited maximum activities in the pH range between 4 and 8, while MBaL-80 was showing maximum activity in the pH range between 3 and 5. Treatment of MBaL-30 and MBaL-60 with EDTA completely abolished their hemagglutinating activities. Addition of Zn and Fe ions to the ethylenediaminetetraacetic acid-treated MBaL-30 and MBaL-60 lectins did not only regained the loss of activity but also resulted in 200% to 300% increase in activity, respectively. MBaL-30 and -60 agglutinated gram positive Listeria monocytogenes and Staphylococcus aureus, whereas MBaL-30 could merely agglutinate Escherichia coli. None of these lectins could arrest bacterial growth. Addition of MBaL to cancer cell lines (Gastric cancer cell line (AGS) and Gastric cencer cell line (MKN45), Glioblastoma (ECV-304), and Human urinary bladder cancer cell line (U87-MG)) at varying concentrations did not cause statistically significant changes on cell growth and viability.

Functional Analysis of a Type-I Ribosome Inactivating Protein Balsamin from Momordica balsamina with Anti-Microbial and DNase Activity

Ribosome inactivating proteins (RIPs) have received considerable attention in biomedical research because of their unique activities towards tumor and virus-infected cells. We extracted balsamin, a type-I RIP, from Momordica balsamina. In the present study, a detailed investigation on DNase activity, antioxidant capacity and antibacterial activity was conducted using purified balsamin. DNase-like activity of balsamin towards plasmid DNA was pH, incubation time and temperature dependent. Moreover, the presence of Mg(2+) (10-50 mM) influenced the DNA cleavage activity. Balsamin also demonstrated reducing power and a capacity to scavenge free radicals in a dose dependent manner. Furthermore, the protein exhibited antibacterial activity against Staphylococcus aureus, Salmonella enterica, Staphylococcus epidermidis and Escherichia coli, which suggests potential utility of balsamin as a nutraceutical.

Ribosome-inactivating proteins (RIPs) and their important health promoting property

Ribosome-inactivating proteins (RIPs), widely present in plants, certain fungi and bacteria, can inhibit protein synthesis by removing one or more specific adenine residues from the large subunit of ribosomal RNAs (rRNAs).

Ribosome-inactivating and related proteins

Ribosome-inactivating proteins (RIPs) are toxins that act as N-glycosidases (EC 3.2.2.22). They are mainly produced by plants and classified as type 1 RIPs and type 2 RIPs. There are also RIPs and RIP related proteins that cannot be grouped into the classical type 1 and type 2 RIPs because of their different sizes, structures or functions. In addition, there is still not a uniform nomenclature or classification existing for RIPs. In this review, we give the current status of all known plant RIPs and we make a suggestion about how to unify those RIPs and RIP related proteins that cannot be classified as type 1 or type 2 RIPs.

PEGylation alleviates the non-specific toxicities of Alpha-Momorcharin and preserves its antitumor efficacy in vivo

Alpha-Momorcharin (α-MMC) is a ribosome inactivating protein from Momordica charantia with anti-tumor activity. Previously, we had observed that modification of α-MMC with polyethylene glycol (PEG) could reduce toxicity, but it also reduces its anti-tumor activity in vitro. This study aims to investigate whether the metabolism-extended properties of α-MMC resulting from PEGylation could preserve its anti-tumor efficacy in vivo through pharmacokinetics and antitumor experiments. The pharmacokinetics experiments were conducted in rats using the TCA (Trichloroacetic Acid) method. Antitumor activity in vivo was investigated in murine mammary carcinoma (EMT-6) and human mammary carcinoma (MDA-MB-231) transplanted tumor mouse models. The results showed that PEGylation increased the plasma half-life of α-MMC in rats from 6.2-7.5 h to 52-87 h. When administered at 1 mg/kg, α-MMC-PEG and α-MMC showed similar anti-tumor activities in vivo, with a T/C% of 38.56% for α-MMC versus 35.43% for α-MMC-PEG in the EMT-6 tumor model and 36.30% for α-MMC versus 39.88% for α-MMC-PEG in the MDA-MB-231 tumor model (p > 0.05). Importantly, at the dose of 3 mg/kg, all the animals treated with α-MMC died while the animals treated with α-MMC-PEG exhibited only moderate toxic reactions, and α-MMC-PEG exhibited improved anti-tumor efficacy with a T/C% (relative tumor growth rate) of 25.18% and 21.07% in the EMT-6 and MDA-MB-231 tumor models, respectively. The present study demonstrates that PEGylation extends the half-life of α-MMC and alleviates non-specific toxicity, thereby preserving its antitumor efficacy in vivo, and a higher lever of dosage can be used to achieve better therapeutic efficacy.

Inhibition of HIV-1 replication by balsamin, a ribosome inactivating protein of Momordica balsamina

Ribosome-inactivating proteins (RIPs) are endowed with several medicinal properties, including antiviral activity. We demonstrate here that the recently identified type I RIP from Momordica balsamina also possesses antiviral activity, as determined by viral growth curve assays and single-round infection experiments. Importantly, this activity is at play even as doses where the RIP has no cytotoxic effect. In addition, balsamin inhibits HIV-1 replication not only in T cell lines but also in human primary CD4⁺ T cells. This antiviral compound exerts its activity at a viral replicative step occurring later than reverse-transcription, most likely on viral protein translation, prior to viral budding and release. Finally, we demonstrate that balsamin antiviral activity is broad since it also impedes influenza virus replication. Altogether our results demonstrate that type I RIP can exert a potent anti-HIV-1 activity which paves the way for new therapeutic avenues for the treatment of viral infections.

Macromolecular interactions of triterpenoids and targeted toxins: role of saponins charge

Macromolecular interaction of protein toxins with certain plant triterpenoids holds potential for application in tumor therapy. The ability of only certain saponins to enhance the endosomal escape of toxins specifically in tumor cells was evaluated and set into correlation with the electrophoretic mobility. Saponins from Saponaria officinalis Linn, were selected as a lead to understand this evolutionarily conserved principle in detail. Agarose gel electrophoresis was utilized to procure pure saponin fractions with different electrophoretic mobility, which were tested for their ability to enhance the toxicity by live cell monitoring. Five fractions (SOG1-SOG5) were isolated with a relative electrophoretic mobility of (-0.05, 0.41, 0.59, 0.75 and 1.00) and evaluated using thin layer chromatography, HPLC, and mass spectroscopic analysis. Cytotoxicity experiments revealed highest effectiveness with SOG3. Live cell imaging experiments with SOG3 revealed that this saponin with a specific REM of 0.59 could assist in the lyso/endosomal release of the toxic payload without affecting the integrity of plasma membrane and could lead to the induction of apoptosis. This charge dependent enhancement was also found to be highly specific to type I ribosome inactivating proteins compared to bacterial toxins. Charge interaction of plant toxins and saponins with tumor cells, plays a major role in toxin specific modulation of response. The finding opens up newer ways of finding protein saponin interaction conserved evolutionarily and to test their role in endosomal escape of therapeutic molecules.

Ribosome inactivating proteins from plants inhibiting viruses

Many plants contain ribosome inactivating proteins (RIPs) with N-glycosidase activity, which depurinate large ribosomal RNA and arrest protein synthesis. RIPs so far tested inhibit replication of mRNA as well as DNA viruses and these proteins, isolated from plants, are found to be effective against a broad range of viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV) and herpes simplex virus (HSV). Most of the research work related to RIPs has been focused on antiviral activity against HIV; however, the exact mechanism of antiviral activity is still not clear. The mechanism of antiviral activity was thought to follow inactivation of the host cell ribosome, leading to inhibition of viral protein translation and host cell death. Enzymatic activity of RIPs is not limited to depurination of the large rRNA, in addition they can depurinate viral DNA as well as RNA. Recently, Phase I/II clinical trials have demonstrated the potential use of RIPs for treating patients with HIV disease. The aim of this review is to focus on various RIPs from plants associated with anti-HIV activity.