Raft-targeting and oligomerization of parasporin-2, a Bacillus thuringiensis crystal protein with anti-tumour activity

Yuichi Abe, Hiroyasu Shimada, Sakae Kitada

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Parasporin-2 is a newly classified Bacillus thuringiensis crystal toxin with strong cytocidal activities toward human liver and colon cancer cells. Similar to other insecticidal B. thuringiensis crystal toxins, parasporin-2 shows target specificity and damages the cellular membrane. However, the mode of parasporin-2 actions toward the cell membrane remains unknown. Here, we show that this anti-tumour crystal toxin targets lipid rafts and assembles into oligomeric complexes in the membrane of human hepatocyte cancer (HepG2) cells. Upon incubation with HepG2 cells, peripheral membrane-bound toxins, which were recovered in a low-density detergent-resistant membrane fraction, i.e. with lipid rafts, were transformed into heat-stable SDS-resistant membrane-embedded oligomers (∼200 kDa). The toxin oligomerization was dependent on temperature and coupled with cell lysis. The toxin oligomerization also occurred in a cell-free membrane system and was required for binding to membrane proteins, the lipid bilayer and cholesterols. These results indicate that parasporin-2 is an oligomerizing and pore-forming toxin that accumulates in lipid rafts.

Original languageEnglish
Pages (from-to)269-275
Number of pages7
JournalJournal of biochemistry
Volume143
Issue number2
DOIs
Publication statusPublished - Feb 2008

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

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