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Cells regulate their developmental and functional programs through their interaction with the external milieu, which requires communication across the plasma membrane. The plasma membrane is constantly being remodeled by endocytosis allowing cells to control how they respond to external stimuli. Endocytosis also allows continuous sampling of the external environment, which is important for the uptake of micronutrients and for the cellular and organismal response to infectious agents. The importance of this process in human health merits its careful study and characterization. For the last nine years, a biannual European conference on endocytosis has been held in various locations. The fifth of these meetings was held September 13–18, in San Feliu de Guixols, a beautiful venue on the Costa Brava in Spain. Besides having the opportunity to scuba dive, the participants followed an interesting and ambitious schedule of oral and poster presentations on the molecular mechanisms involved in endocytosis and how these mechanisms relate to health and disease.

Natamycin is a polyene antibiotic that is commonly used as an antifungal agent because of its broad spectrum of activity and the lack of development of resistance. Other polyene antibiotics, like nystatin and filipin are known to interact with sterols, with some specificity for ergosterol thereby causing leakage of essential components and cell death. The mode of action of natamycin is unknown and is investigated in this study using different in vitro and in vivo approaches. Isothermal titration calorimetry and direct binding studies revealed that natamycin binds specifically to ergosterol present in model membranes. Yeast sterol biosynthetic mutants revealed the importance of the double bonds in the B-ring of ergosterol for the natamycin-ergosterol interaction and the consecutive block of fungal growth. Surprisingly, in strong contrast to nystatin and filipin, natamycin did not change the permeability of the yeast plasma membrane under conditions that growth was blocked. Also, in ergosterol containing model membranes, natamycin did not cause a change in bilayer permeability. This demonstrates that natamycin acts via a novel mode of action and blocks fungal growth by binding specifically to ergosterol

Using small molecule probes to understand gene function is an attractive approach that allows functional characterization of genes that are dispensable in standard laboratory conditions and provides insight into the mode of action of these compounds. Using chemogenomic assays we previously identified yeast Crg1 an uncharacterized SAM dependent methyltransferase as a novel interactor of the protein phosphatase inhibitor cantharidin. In this study we used a combinatorial approach that exploits contemporary high throughput techniques available in Saccharomyces cerevisiae combined with rigorous biological follow up to characterize the interaction of Crg1 with cantharidin. Biochemical analysis of this enzyme followed by a systematic analysis of the interactome and lipidome of CRG1 mutants revealed that Crg1 a stress responsive SAM dependent methyltransferase methylates cantharidin in vitro. Chemogenomic assays uncovered that lipid related processes are essential for cantharidin resistance in cells sensitized by deletion of the CRG1 gene. Lipidome wide analysis of mutants further showed that cantharidin induces alterations in glycerophospholipid and sphingolipid abundance in a Crg1 dependent manner. We propose that Crg1 is a small molecule methyltransferase important for maintaining lipid homeostasis in response to drug perturbation. This approach demonstrates the value of combining chemical genomics with other systems based methods for characterizing proteins and elucidating previously unknown mechanisms of action of small molecule inhibitors.