Cytotoxic Effects and Intracellular Localization of Bin Toxin from Lysinibacillus sphaericus in Human Liver Cancer Cell Line

Abstract

Binary toxin (Bin toxin), BinA and BinB, produced by Lysinibacillus sphaericus has been used as a mosquito-control agent due to its high toxicity against the mosquito larvae. The crystal structures of Bin toxin and non-insecticidal but cytotoxic parasporin-2 toxin share some common structural features with those of the aerolysin-like toxin family, thus suggesting a common mechanism of pore formation of these toxins. Here we explored the possible cytotoxicity of Bin proteins (BinA, BinB and BinA + BinB) against Hs68 and HepG2 cell lines. The cytotoxicity of Bin proteins was evaluated using the trypan blue exclusion assay, MTT assay, morphological analysis and LDH efflux assay. The intracellular localization of Bin toxin in HepG2 cells was assessed by confocal laser scanning microscope. HepG2 cells treated with BinA and BinB (50 µg/mL) showed modified cell morphological features and reduced cell viability. Bin toxin showed no toxicity against Hs68 cells. The EC50 values against HepG2 at 24 h were 24 ng/mL for PS2 and 46.56 and 39.72 µg/mL for BinA and BinB, respectively. The induction of apoptosis in treated HepG2 cells was confirmed by upregulation of caspase levels. The results indicated that BinB mediates the translocation of BinA in HepG2 cells and subsequently associates with mitochondria. The study supports the possible development of Bin toxin as either an anticancer agent or a selective delivery vehicle of anticancer agents to target mitochondria of human cancer cells in the future.

Random Mutational Analysis Targeting Residue K155 within the Transmembrane β-Hairpin of the Mosquitocidal Mpp46Ab Toxin

“…Both BinA and BinB are members of aerolysintype β-PFTs and share some structural features with Mpp46Aa (PS2Aa) [11]. Potential application to cancer therapy has been assessed and it has been demonstrated that a high concentration of trypsin-activated Bin toxin (particularly BinB subunit) inhibited cell proliferation of human cancer cell lines [31,32]. Comparative analysis, particularly associated with receptor binding, may help to explore the determinants of the specificity of Mpp46Ab as well as Bin toxins.…”

The Combined Antioxidant Effects of N-Acetylcysteine, Vitamin D3, and Glutathione from the Intestinal–Neuronal In Vitro Model

“…A total of 2 × 10 5 cells were plated on Transwell ® system to perform the LA quantification and permeability assay by 0.04% fluorescein (Merck Life Science, Rome, Italy). A total of 2 ×10 4 cells were plated in 96-well plates for the analysis of cell viability by MTT test (Merck Life Science, Rome, Italy) [ 33 ].…”

Mosquito-larvicidal Binary (BinA/B) proteins for mosquito control programs —advancements, challenges, and possibilities

“…The binary toxin is also being studied for its therapeutic role as a potential anti-cancer agent (Luo et al., 2014) . Reportedly, the binary toxin induces apoptotic events in human cancer lines (Chankamngoen, Janvilisri, Promdonkoy and Boonserm, 2020) and targets the mitochondria (Kanwal, Abeysinghe, Srisaisup and Boonserm, 2021) .…”