Distinct localization of lipid rafts and externalized phosphatidylserine at the surface of apoptotic cells.
Externalization of phosphatidylserine (PS) takes place in apoptotic cells as well as in viable cells under certain circumstances. Recent studies showed that externalized PS is localized at the lipid raft in viable activated immune cells. We found that lipid rafts and PS existed in a mutually exclusive manner in apoptotic cells. The number of PS-exposing apoptotic cells decreased when lipid rafts were disrupted. BCtheta;, which binds selectively to cholesterol in a cholesterol-rich region, did not effectively recognize lipid rafts of apoptotic cells. Lipid rafts rich in GM1 were successfully prepared from apoptotic cells, but the lipid raft protein LAT was not enriched in the preparation. Furthermore, the amount of PS and phosphatidylethanolamine but not of cholesterol in lipid rafts appeared to change after induction of apoptosis. These results suggest that lipid rafts are structurally modified during apoptosis and, despite being localized differently from PS, are involved in the externalization of PS.
Ishii
Hidenari
H
Graduate School of Medical Science, Kanazawa University, Shizenken, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
Mori
Tomoe
T
Shiratsuchi
Akiko
A
Nakai
Yuji
Y
Shimada
Yukiko
Y
Ohno-Iwashita
Yoshiko
Y
Nakanishi
Yoshinobu
Y
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability; D006801:Humans; D019169:Jurkat Cells; D021962:Membrane Microdomains / Q000737:chemistry* / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000494:pharmacology
D010718:Phosphatidylserines; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin