Drug Uptake, Lipid Rafts, and Vesicle Trafficking Modulate Resistance to an Anticancer Lysophosphatidylcholine Analogue in Yeast

Abstract

Background:The antitumor lipid edelfosine kills yeast by inducing selective internalization of raft-associated proteins. Results: Impairing vesicular trafficking to the vacuole counteracted edelfosine-induced plasma membrane alterations without affecting internalization of the drug. Conclusion: Recycling of raft-associated proteins to the plasma membrane prevents edelfosine cytotoxicity. Significance: Vesicular trafficking is a critical process mediating edelfosine resistance in yeast that could be extrapolated to tumor cells.

Alteration of Plasma Membrane Organization by an Anticancer Lysophosphatidylcholine Analogue Induces Intracellular Acidification and Internalization of Plasma Membrane Transporters in Yeast

“…In line with this rationale, a novel role for mitochondria in the maintenance of pH homeostasis has been recently unveiled (41). Furthermore, our resistance genetic screen was enriched in mitochondrial functional categories (69), suggesting impaired respiration alleviates edelfosine sensitivity. Another possibility is that edelfosine, or its effect on intracellular ergosterol accumulation, may affect proper V-ATPase assembly/ function that is expected to confer susceptibility to high pH ext (41,55).…”

“…These categories were also enriched in our resistance genetic screen presented in the accompanying paper (69). Of particular interest is the fact that the same phospholipid flippases mediating edelfosine uptake emerged as pH regulators, as did retromer and ESCRT mutants (55).…”

“…Therefore, we propose that during the 1st h, the effect of edelfosine is mostly cytostatic due to lack of nutrient uptake. After 1 h, edelfosine uptake reaches a maximum and accumulates in the endoplasmic reticulum (6,69). Therefore, cells that can correct the changes induced by edelfosine at the PM would be able to resume growth despite the intracellular accumulation of edelfosine.…”

“…6c). Furthermore, the unbiased results from our chemogenomic screen testing for enhanced resistance to edelfosine (69) identified genes involved in maintenance of the ubiquitin pool, E3-ubiquitin ligase adaptor proteins, as well as mutants of pathways that recognize ubiquitinated cargo like the ESCRT and retromer systems. Together, these results indicate that edelfosine induces exit of sterols and Pma1p from the PM followed by Pma1p internalization and degradation in a ubiquitin-mediated process.…”

“…3a). Moreover, Vps35p is a component of the yeast retromer, and cells with an inactivated VPS35 gene are resistant to edelfosine, although uptake of the drug is normal (69). A time frame of 90 min was chosen as we have previously determined it precedes cell death (6).…”