Bad-dependent rafts alteration is a consequence of an early intracellular signal triggered by interleukin-4 deprivation.
Many molecules are inducibly localized in lipid rafts, and their alteration inhibits early activation events, supporting a critical role for these domains in signaling. Using confocal microscopy and cellular fractionation, we have shown that the pool of Bad, attached to lipid rafts in proliferating cells, is released when cells undergo apoptosis. Kinetic studies indicate that rafts alteration is a consequence of an intracellular signal triggered by interleukin-4 deprivation. Growth factor deprivation in turn induces PP1alpha phosphatase activation, responsible for cytoplasmic Bad dephosphorylation as well as caspase-9 and caspase-3 activation. Caspases translocate to rafts and induce their modification followed by translocation of Bad from rafts to mitochondria, which correlates with apoptosis. Taken together, our results suggest that alteration of lipid rafts is an early event in the apoptotic cascade indirectly induced by interleukin-4 deprivation via PP1alpha activation, dephosphorylation of cytoplasmic Bad, and caspase activation.
Fleischer
Aarne
A
Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière, Bâtiment CERVI, 83, Boulevard de l'Hôpital, 75013 Paris, France.
Ghadiri
Ata
A
Dessauge
Frédéric
F
Duhamel
Marianne
M
Cayla
Xavier
X
Garcia
Alphonse
A
Rebollo
Angelita
A
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D002772:Cholera Toxin / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D047468:Immunoprecipitation; D015847:Interleukin-4 / Q000378:metabolism*; D007700:Kinetics; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D017830:Octoxynol / Q000494:pharmacology; D019319:Okadaic Acid / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology; D013997:Time Factors; D051025:bcl-Associated Death Protein
C494820:Bad protein, mouse; D002352:Carrier Proteins; D051025:bcl-Associated Death Protein; D019319:Okadaic Acid; D015847:Interleukin-4; D017830:Octoxynol; D002772:Cholera Toxin; D010749:Phosphoprotein Phosphatases; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases