Regulation of autophagy by sphingosine kinase 1 and its role in cell survival during nutrient starvation.
The sphingolipid ceramide induces macroautophagy (here called autophagy) and cell death with autophagic features in cancer cells. Here we show that overexpression of sphingosine kinase 1 (SK1), an enzyme responsible for the production of sphingosine 1-phosphate (S1P), in MCF-7 cells stimulates autophagy by increasing the formation of LC3-positive autophagosomes and the rate of proteolysis sensitive to the autophagy inhibitor 3-methyladenine. Autophagy was blocked in the presence of dimethylsphingosine, an inhibitor of SK activity, and in cells expressing a catalytically inactive form of SK1. In SK1(wt)-overexpressing cells, however, autophagy was not sensitive to fumonisin B1, an inhibitor of ceramide synthase. In contrast to ceramide-induced autophagy, SK1(S1P)-induced autophagy is characterized by (i) the inhibition of mammalian target of rapamycin signaling independently of the Akt/protein kinase B signaling arm and (ii) the lack of robust accumulation of the autophagy protein Beclin 1. In addition, nutrient starvation induced both the stimulation of autophagy and SK activity. Knocking down the expression of the autophagy protein Atg7 or that of SK1 by siRNA abolished starvation-induced autophagy and increased cell death with apoptotic hallmarks. In conclusion, these results show that SK1(S1P)-induced autophagy protects cells from death with apoptotic features during nutrient starvation.
Lavieu
Grégory
G
INSERM U504, Institut André Lwoff, 94807 Villejuif Cedex, France, INSERM U756, Faculté de Pharmacie, Université Paris-Sud, 92296 Châtenay-Malabry, France.
Scarlatti
Francesca
F
Sala
Giusy
G
Carpentier
Stéphane
S
Levade
Thierry
T
Ghidoni
Riccardo
R
Botti
Joëlle
J
Codogno
Patrice
P
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D002518:Ceramides / Q000032:analysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007790:Lactosylceramides / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010739:Phospholipase D / Q000032:analysis; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013217:Starvation; D058570:TOR Serine-Threonine Kinases; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism; D000099157:Sphingosine Kinase
D000225:Adenine; D051017:Apoptosis Regulatory Proteins; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D002518:Ceramides; D004791:Enzyme Inhibitors; D049452:Green Fluorescent Proteins; D007790:Lactosylceramides; D008565:Membrane Proteins; D010739:Phospholipase D; D017853:Phosphotransferases (Alcohol Group Acceptor); D011494:Protein Kinases; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases; D044764:Ubiquitin-Activating Enzymes; D000099157:Sphingosine Kinase; C491997:BECN1 protein, human; C025946:3-methyladenine; C025575:lactotriaosylceramide; C546842:MTOR protein, human; C509349:ATG7 protein, human