title: Mode of action of parasporin-4, a cytocidal protein from Bacillus thuringiensis.
abstract: Parasporin-4 (PS4) is a cytotoxic protein produced by Bacillus thuringiensis strain A1470. It exhibits specific cytotoxicity against human cancer cell lines, CACO-2, Sawano, and MOLT-4 cells, in particular. When cells were administrated with PS4, cell swelling and nuclear shrinkage were induced, and, the ballooned cells burst within 24 h. PSI-BLAST search showed that the protein shared homology not only with B. thuringiensis Cry toxins but also with aerolysin-type β-pore-forming toxins. Circular dichroism measurements suggested that PS4 was a β-sheet-rich protein. PS4 aggregated into oligomers on the plasma membrane of PS4-susceptible CACO-2 cells, but not on that of PS4-resistant HeLa cells. Leakage of lactate dehydrogenase and influx of extracellular FITC-dextrans were observed only in susceptible cells. The activation of effectors caspase 3 and/or 7 was not observed in PS4-treated CACO-2 cells. It was shown that cytotoxicity of the PS4 against CACO-2 cells was exhibited when treated by cyclodextrin which induces cholesterol depletion. These results suggest that PS4 is a unique β-pore-forming toxin with a cholesterol-independent activity.
authors.affiliation: Fukuoka Industrial Technology Centre, 1465-5 Aikawa, Kurume, Fukuoka 839-0861, Japan. sokumura@fitc.pref.fukuoka.jp
authors.forename: Shiro
authors.initials: S
authors.lastname: Okumura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saitoh
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Kuniyo
authors.initials: K
authors.lastname: Inouye
authors.forename: Eiichi
authors.initials: E
authors.lastname: Mizuki
mesh_terms: D000924:Anticholesteremic Agents / Q000494:pharmacology; D001413:Bacillus thuringiensis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D018938:Caco-2 Cells; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000378:metabolism; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D020014:K562 Cells; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008148:Lovastatin / Q000494:pharmacology; D008858:Microscopy, Phase-Contrast; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding; D055503:Protein Multimerization
chemical_list: D000924:Anticholesteremic Agents; D001426:Bacterial Proteins; D004731:Endotoxins; C412914:parasporin; C559658:parasporin-4, Bacillus thuringiensis; D002784:Cholesterol; D008148:Lovastatin; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D053179:Caspase 7