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The rise of antimicrobial resistance poses a severe threat to public health. The natural product chlorotonil was identified as a new antibiotic targeting multidrug resistant Gram-positive pathogens and Plasmodium falciparum. Although chlorotonil shows promising activities, the scaffold is highly lipophilic and displays potential biological instabilities. Therefore, we strived towards improving its pharmaceutical properties by semisynthesis. We demonstrated stereoselective epoxidation of chlorotonils and epoxide ring opening in moderate to good yields providing derivatives with significantly enhanced solubility. Furthermore, in vivo stability of the derivatives was improved while retaining their nanomolar activity against critical human pathogens (e.g. methicillin-resistant Staphylococcus aureus and P. falciparum). Intriguingly, we showed further superb activity for the frontrunner molecule in a mouse model of S. aureus infection.

Autophagy mediates the degradation of damaged proteins, organelles and pathogens, and plays a key role in health and disease. Thus, the identification of new mechanisms involved in the regulation of autophagy is of major interest. In particular, little is known about the role of lipids and lipid-binding proteins in the early steps of autophagosome biogenesis. Using target-agnostic, high-content, image-based identification of indicative phenotypic changes induced by small molecules, we have identified autogramins as a new class of autophagy inhibitor. Autogramins selectively target the recently discovered cholesterol transfer protein GRAM domain-containing protein 1A (GRAMD1A, which had not previously been implicated in autophagy), and directly compete with cholesterol binding to the GRAMD1A StART domain. GRAMD1A accumulates at sites of autophagosome initiation, affects cholesterol distribution in response to starvation and is required for autophagosome biogenesis. These findings identify a new biological function of GRAMD1A and a new role for cholesterol in autophagy.

The acyl‐binding UNC119 proteins mediate the activation and transport of various N‐myristoylated proteins. In particular, UNC119a plays a crucial role in the completion of cytokinesis. Herein, we report the use of a lipidated peptide originating from the UNC119 binding partner Gnat1 as the basis for the design of lipidated, stabilized α‐helical peptides that target UNC119a. By using the hydrocarbon peptide‐stapling approach, cell‐permeable binders of UNC119a were generated that induced the accumulation of cytokinetic and binucleated cells; this suggests UNC119a as a potential target for the inhibition of cytokinesis., Targeting molecular chaperones: Cell‐permeable peptidomimetics of a myristoylated peptide were obtained by hydrocarbon peptide stapling. These agents target the human acyl‐binding protein UNC119a, which plays a crucial role in cytokinesis, inducing the accumulation of cytokinetic and binucleated cells. This suggests UNC119a as a potential target for the inhibition of cytokinesis.

Summary Interference with the signaling activity of the N-myristoylated nonreceptor protein tyrosine kinase Src is considered a viable approach in anti-cancer drug discovery. However, ATP-competitive Src inhibitors have not reached the clinic yet and alternative approaches are in high demand. The UNC119A/B proteins bind the myristoylated N terminus of Src and thereby mediate energy-driven spatial cycles that maintain Src enrichment at the plasma membrane, which is critical for Src signaling activity. We describe the discovery of a potent and specific inhibitor of the UNC119-Src interaction with unprecedented chemotype. The inhibitor binds to UNC119 in cells, and induces redistribution of Src to endomembranes and reduction of activating Src autophosphorylation on Y419. UNC119 inhibition in Src-dependent colorectal cancer cells results in the specific reduction of cell growth and clonogenic potential. Our results demonstrate that small-molecule interference with the dynamics of the Src spatial cycle may provide an opportunity to impair oncogenic Src signaling.

We describe a simple and sensitive method for enhancement of the silver-gold-intensified 3,3'-diaminobenzidine (DAB) reaction demonstrating peroxidase activity. After completing silver-gold intensification of the preparations immunostained by the avidin-biotin-peroxidase method with DAB as the chromogen, the preparations were immersed in a solution containing uranyl nitrate. This new method appeared to increase the sensitivity by at least one order of magnitude as compared with silver-gold intensification alone.