Purification and characterization of a novel high molecular weight exotoxin produced by red tide phytoplankton, Alexandrium tamarense.
Our recent studies have demonstrated that the aqueous extract prepared from Alexandrium tamarense, a harmful red tide phytoplankton, showed cytotoxicity on Vero cells. In this study, the toxic substance was purified from the culture supernatant of A. tamarense. Based on the gel-filtration profile, the molecular mass of a purified toxin was estimated to be about 1,000 kDa. On sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, a main band with molecular mass of 1,000 kDa was detected with periodic acid-Schiff (PAS) staining, but no protein bands were detected by Coomassie brilliant blue (CBB) protein staining. Sugar composition analysis of the toxin suggested that the toxin contains galactose, fucose, mannose, N-acetylglucosamine, xylose, and other minor saccharides, whereas no significant levels of amino acids were detected by amino acid analysis. These results suggest that the toxin is a polysaccharide-based compound. The toxin showed cytotoxic effects on various cell lines in a concentration-dependent manner. Among the cell lines tested, U937 cells were the most susceptible to the toxin. In U937 cells treated with the toxin, a typical apoptotic nuclear morphological change and DNA fragmentation were observed. This is the first report demonstrating that a polysaccharide-based toxin isolated from red tide phytoplankton can induce apoptotic cell death.
Yamasaki
Yasuhiro
Y
Division of Biochemistry, Faculty of Fisheries, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan.
Katsuo
Daisuke
D
Nakayasu
Seiichiro
S
Salati
Cristina
C
Duan
JingJing
J
Zou
Yanan
Y
Matsuyama
Yukihiko
Y
Yamaguchi
Kenichi
K
Oda
Tatsuya
T
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002474:Cell-Free System; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D053938:DNA Fragmentation / Q000187:drug effects; D004141:Dinoflagellida / Q000737:chemistry* / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005098:Exotoxins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism* / Q000494:pharmacology; D006367:HeLa Cells; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008970:Molecular Weight; D010839:Phytoplankton / Q000737:chemistry* / Q000166:cytology; D011134:Polysaccharides / Q000737:chemistry; D011817:Rabbits; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D020298:U937 Cells; D014709:Vero Cells
D004791:Enzyme Inhibitors; D005098:Exotoxins; D011134:Polysaccharides