YAMATO Kenji Tokyo Medical and Dental University, Dentistry, Lecturer, 歯学部, 講師 (50174751)
AKIFUSA Sumio Kyushu Dental College, Dentistry, Special Researcher, 歯学部, 特別研修員 (40295861)
TSUJISAWA Toshiyuki Kyushu Dental College, Dentistry, Assistant, 歯学部, 助手 (60265006)
|Budget Amount *help
¥12,800,000 (Direct Cost: ¥12,800,000)
Fiscal Year 2005: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2004: ¥7,300,000 (Direct Cost: ¥7,300,000)
Actinobacillus actinomycetemcomitans produces a toxin, called cytolethal distending toxin (CDT), which causes host cell DNA damage leading to the induction of DNA damage checkpoint pathways. CDT consists of three subunits, CdtA, CdtB, and CdtC CdtB is the active subunit of CDT and exerts its effect as a nuclease that damages nuclear DNA, triggering cell cycle arrest. In the present study, we confirmed that the only combination of toxin proteins causing cell cycle arrest was that of all three recombinant CDT (rCDT) protein subunits. Furthermore, in order for rCDT to demonstrate toxicity, it was necessary for CdtA and CdtC to access the cell before CdtB. The coexistence of CdtA and CdtC was necessary for these subunits to bind to the cell. Cells treated with the glucosylceramide synthesis inhibitor 1-phenyl-2-palmitoylamino-3-morpholino-1-propanol showed resistance to the cytotoxicity induced by rCDT. Furthermore, LY-B cells, which are deficient in the biosynthesis of sphingolipid, also showed resistance to the cytotoxicity induced by rCDT. To evaluate the binding of each subunit for glucosylceramides, we performed thin-layer chromatography immunostaining. The results indicated that each subunit reacted with the GM1, GM2, GM3, Gb3, and Gb4. The rCDT mixture incubated with liposomes containing GM3 displayed partially reduced toxicity. These results indicate that GM3 can act as a CDT receptor.