Visit our Expo - Redox and Inflammation signaling 2012

Session X : Cell death in cancer Poster X, 56
Regulation of autophagy by sphingosine kinase 1 and its role in cell survival during
nutrient starvation*
Grégory Lavieu†, Francesca Scarlatti§, Giusy Sala§, Thierry Levade‡, Riccardo
Ghidoni§, Joëlle Botti† and Patrice Codogno†
†INSERM U504, Institut André Lwoff, 16 avenue Paul-Vaillant-Couturier, 94807
Villejuif Cedex France, §Laboratory of Biochemistry and Molecular Biology, San Paolo
Medical School, via A. di Rudinì 8, 20142 Milan Italy, ‡INSERM U466, Institut Louis
Bugnard, Centre Hospitalier Universitaire de Rangueil, BP 84225, 31432 Toulouse
Cedex 4 France..
The sphingolipid ceramide induces macroautophagy (here called autophagy) and cell death
with autophagic features in cancer cells (1, 2). Here we show that overexpression of
sphingosine kinase 1 (SK1), an enzyme responible for the production of sphingosine 1phosphate
(S1P), stimulates autophagy by increasing the formation of LC3 positive
autophagosomes and the rate of proteolysis sentitive to the autophagy inhibitor 3methyladenine.
Furthermore, autophagy was blocked in the presence of dimethylsphingosine,
an inhibitor of SK activity and in cells expressing a catalytically inactive form of SK1. In
contrast to ceramide-induced autophagy, SK1(S1P)-induced autophagy was characterized : 1by
the inhibition of mTOR signaling independently of the Akt/PKB signaling arm, 2-the lack
of robust accumulation of the autophagy protein Beclin 1. In addition, nutrient starvation
induced both the stimulation of autophagy and SK activity. Silencing the expression of the
autophagy protein Atg7 or that of SK1 by siRNA abolished starvation-induced autophagy and
exacerbated cell death with apoptotic hallmarks. In conclusion, these results show that
SK1(S1P)-induced autophagy protects cells from death with apoptotic features during nutrient
deprivation.
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