Cytocidal actions of parasporin-2, an anti-tumor crystal toxin from Bacillus thuringiensis.
Parasporin-2, a new crystal protein derived from noninsecticidal and nonhemolytic Bacillus thuringiensis, recognizes and kills human liver and colon cancer cells as well as some classes of human cultured cells. Here we report that a potent proteinase K-resistant parasporin-2 toxin shows specific binding to and a variety of cytocidal effects against human hepatocyte cancer cells. Cleavage of the N-terminal region of parasporin-2 was essential for the toxin activity, whereas C-terminal digestion was required for rapid cell injury. Protease-activated parasporin-2 induced remarkable morphological alterations, cell blebbing, cytoskeletal alterations, and mitochondrial and endoplasmic reticulum fragmentation. The plasma membrane permeability was increased immediately after the toxin treatment and most of the cytoplasmic proteins leaked from the cells, whereas mitochondrial and endoplasmic reticulum proteins remained in the intoxicated cells. Parasporin-2 selectively bound to cancer cells in slices of liver tumor tissues and susceptible human cultured cells and became localized in the plasma membrane until the cells were damaged. Thus, parasporin-2 acts as a cytolysin that permeabilizes the plasma membrane with target cell specificity and subsequently induces cell decay.
Kitada
Sakae
S
Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan. s.kitscc@mbox.nc.kyushu-u.ac.jp
Abe
Yuichi
Y
Shimada
Hiroyasu
H
Kusaka
Yoshitomo
Y
Matsuo
Yoko
Y
Katayama
Hideki
H
Okumura
Shiro
S
Akao
Tetsuyuki
T
Mizuki
Eiichi
E
Kuge
Osamu
O
Sasaguri
Yasuyuki
Y
Ohba
Michio
M
Ito
Akio
A
D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001413:Bacillus thuringiensis / Q000737:chemistry*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D048430:Cell Shape; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D019286:Endopeptidase K / Q000378:metabolism; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D000970:Antineoplastic Agents; D001427:Bacterial Toxins; D004731:Endotoxins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C412914:parasporin; C515506:parasporin-2, Bacillus thuringiensis; D019286:Endopeptidase K