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Naja atra Cardiotoxin 3 Elicits Autophagy and Apoptosis in U937 Human Leukemia Cells through the Ca2+/PP2A/AMPK Axis.

ABSTRACT: Cardiotoxins (CTXs) are suggested to exert their cytotoxicity through cell membrane damage. Other studies show that penetration of CTXs into cells elicits mitochondrial fragmentation or lysosome disruption, leading to cell death. Considering the role of AMPK-activated protein kinase (AMPK) in mitochondrial biogenesis and lysosomal biogenesis, we aimed to investigate whether the AMPK-mediated pathway modulated Naja atra (Taiwan cobra) CTX3 cytotoxicity in U937 human leukemia cells. Our results showed that CTX3 induced autophagy and apoptosis in U937 cells, whereas autophagic inhibitors suppressed CTX3-induced apoptosis. CTX3 treatment elicited Ca2+-dependent degradation of the protein phosphatase 2A (PP2A) catalytic subunit (PP2Ac?) and phosphorylation of AMPK?. Overexpression of PP2Ac? mitigated the CTX3-induced AMPK? phosphorylation. CTX3-induced autophagy was via AMPK-mediated suppression of the Akt/mTOR pathway. Removal of Ca2+ or suppression of AMPK? phosphorylation inhibited the CTX3-induced cell death. CTX3 was unable to induce autophagy and apoptosis in U937 cells expressing constitutively active Akt. Met-modified CTX3 retained its membrane-perturbing activity, however, it did not induce AMPK activation and death of U937 cells. These results conclusively indicate that CTX3 induces autophagy and apoptosis in U937 cells via the Ca2+/PP2A/AMPK axis, and suggest that the membrane-perturbing activity of CTX3 is not crucial for the cell death signaling pathway induction.

SUBMITTER: Chiou JT

PROVIDER: S-EPMC6784133 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Naja atra Cardiotoxin 3 Elicits Autophagy and Apoptosis in U937 Human Leukemia Cells through the Ca2+/PP2A/AMPK Axis.

Chiou Jing-Ting JT Shi Yi-Jun YJ Wang Liang-Jun LJ Huang Chia-Hui CH Lee Yuan-Chin YC Chang Long-Sen LS

Toxins 20190912 9

Cardiotoxins (CTXs) are suggested to exert their cytotoxicity through cell membrane damage. Other studies show that penetration of CTXs into cells elicits mitochondrial fragmentation or lysosome disruption, leading to cell death. Considering the role of AMPK-activated protein kinase (AMPK) in mitochondrial biogenesis and lysosomal biogenesis, we aimed to investigate whether the AMPK-mediated pathway modulated Naja atra (Taiwan cobra) CTX3 cytotoxicity in U937 human leukemia cells. Our res ...[more]

PMID: 31547294

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Project description:Naja atra subsp. atra cardiotoxin 1 (CTX-1), produced by Chinese cobra snakes, belonging to Elapidae family, is included in the three-finger toxin family and exerts high cytotoxicity and antimicrobial activity too. Using as template mainly the tip and the subsequent β-strand of the first "finger" of this toxin, different sequences of 20 amino acids linear peptides have been designed in order to avoid toxic effects but to maintain or even strengthen the partial antimicrobial activity already seen for the complete toxin. As a result, the sequence NCP-0 (Naja Cardiotoxin Peptide-0) was designed as ancestor and subsequently 4 other variant sequences of NCP-0 were developed. These synthesized variant sequences have shown microbicidal activity towards a panel of reference and field strains of Gram-positive and Gram-negative bacteria. The sequence named NCP-3, and its variants NCP-3a and NCP-3b, have shown the best antimicrobial activity, together with low cytotoxicity against eukaryotic cells and low hemolytic activity. Bactericidal activity has been demonstrated by minimum bactericidal concentration (MBC) assay at values below 10 μg/ml for most of the tested bacterial strains. This potent antimicrobial activity was confirmed even for unicellular fungi Candida albicans, Candida glabrata and Malassezia pachydermatis (MBC 50-6.3 μg/ml), and against the fast-growing mycobacteria Mycobacterium smegmatis and Mycobacterium fortuitum. Moreover, NCP-3 has shown virucidal activity on Bovine Herpesvirus 1 (BoHV1) belonging to Herpesviridae family. The bactericidal activity is maintained even in a high salt concentration medium (125 and 250 mM NaCl) and phosphate buffer with 20% Mueller Hinton (MH) medium against E. coli, methicillin resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa reference strains. Considering these in vitro obtained data, the search for active sequences within proteins presenting an intrinsic microbicidal activity could provide a new way for discovering a large number of novel and promising antimicrobial peptides families.

Dataset Information

Naja atra Cardiotoxin 3 Elicits Autophagy and Apoptosis in U937 Human Leukemia Cells through the Ca2+/PP2A/AMPK Axis.

Publications

<i>Naja atra</i> Cardiotoxin 3 Elicits Autophagy and Apoptosis in U937 Human Leukemia Cells through the Ca<sup>2+</sup>/PP2A/AMPK Axis.

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