Abstract
We have previously established that the anti-cancer lysophospholipid edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, Et-18-OCH(3)) induces cell death in yeast by selective modification of lipid raft composition at the plasma membrane. In this study we determined that alpha-tocopherol protects cells from the edelfosine cytotoxic effect, preventing the internalization of sterols and the plasma membrane proton pump ATPase, Pma1p. Two non-mutually exclusive hypotheses were considered to explain the protective effect of alpha-tocopherol: (i) its classical antioxidant activity is necessary to break progression of lipid peroxidation, despite the fact Saccharomyces cerevisiae does not possess polyunsaturated fatty acids and (ii) due to its complementary cone shape, insertion of alpha-tocopherol could correct membrane curvature stress imposed by edelfosine (inverted cone shape). We then developed tools to distinguish between these two hypotheses and dissect the structural requirements that confer alpha-tocopherol its protective effect. Our results indicated its lipophilic nature and the H donating hydroxyl group from the chromanol ring are both required to counteract the cytotoxic effect of edelfosine, suggesting edelfosine induces oxidation of membrane components. To further support this finding and learn more about the early cellular response to edelfosine we investigated the role that known oxidative stress signaling pathways play in modulating sensitivity to the lipid drug. Our results indicate the transcription factors Yap1 and Skn7 as well as the major peroxiredoxin, Tsa1, mediate a response to edelfosine. Interestingly, the pathway differed from the one triggered by hydrogen peroxide and its activation (measured as Yap1 translocation to the nucleus) was abolished by co-treatment of the cells with alpha-tocopherol.
Highlights
Our studies in yeast using unbiased genetic screens have implicated sphingolipid and sterol metabolism as important modulators of edelfosine cytotoxicity [2]
To examine the impact edelfosine has on membrane structure and to gain insight into relevant steps associated with its mode of action, we aimed to study the nature of the vitamin E
Tools were developed to distinguish between two hypotheses: (i) ␣-tocopherol acts as an antioxidant and prevents edelfosine-induced lipid peroxidation, or (ii) the ␣-tocopherol protective effect is due to a non-antioxidant activity, like membrane curvature stress correcis followed by Pma1p endocytosis and degradation in the vacu- tion due to its complementary cone shape in the presence of edelole
Summary
Our studies in yeast using unbiased genetic screens have implicated sphingolipid and sterol metabolism as important modulators of edelfosine cytotoxicity [2]. It has been reported that ␣-TOS exerts a protective effect in edelfosine-treated yeast cells [8]. This is intriguing, because in addition, Saccharomyces cerevisiae lacks polyunsaturated fatty acids [17, 18]. Resistance to the drug has been observed in triggers an oxidative stress response that is prevented in the prescells able to recycle internalized lipid/proteins back to the ence of ␣-tocopherol. This response differs from the one elicited plasma membrane [2]. Three major were grown to mid-log phase in yeast complex medium
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
