Search

Post-translational modifications (PTMs) of proteins are ubiquitous processes present in all life kingdoms, involved in the regulation of protein stability, subcellular location and activity. In this context, cytochrome c (Cc) is an excellent case study to analyze the structural and functional changes induced by PTMS as Cc is a small, moonlighting protein playing different roles in different cell compartments at different cell-cycle stages. Cc is actually a key component of the mitochondrial electron transport chain (ETC) under homeostatic conditions but is translocated to the cytoplasm and even the nucleus under apoptotic conditions and/or DNA damage. Phosphorylation does specifically alter the Cc redox activity in the mitochondria and the Cc non-redox interaction with apoptosis-related targets in the cytoplasm. However, little is known on how phosphorylation alters the interaction of Cc with histone chaperones in the nucleus. Here, we report the effect of Cc Tyr48 phosphorylation by examining the protein interaction with SET/TAF-Iβ in the nuclear compartment using a combination of molecular dynamics simulations, biophysical and structural approaches such as isothermal titration calorimetry (ITC) and nuclear magnetic resonance (NMR) and in cell proximity ligation assays. From these experiments, we infer that Tyr48 phosphorylation allows a fine-tuning of the Cc-mediated inhibition of SET/TAF-Iβ histone chaperone activity in vitro. Our findings likewise reveal that phosphorylation impacts the nuclear, stress-responsive functions of Cc, and provide an experimental framework to explore novel aspects of Cc post-translational regulation in the nucleus., (© 2024 The Author(s). Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

The human microbiota plays an important role in human health and disease, through the secretion of metabolites that regulate key biological functions. We propose that microbiota metabolites represent an unexplored chemical space of small drug-like molecules in the search of new hits for drug discovery. Here, we describe the generation of a set of complex chemotypes inspired on selected microbiota metabolites, which have been synthesized using asymmetric organocatalytic reactions. Following a primary screening in CSC models, we identified the novel compound UCM-13369 ( 4b ) whose cytotoxicity was mediated by NPM1. This protein is one of the most frequent mutations of AML, and NPM1-mutated AML is recognized by the WHO as a distinct hematopoietic malignancy. UCM-13369 inhibits NPM1 expression, downregulates the pathway associated with mutant NPM1 C+, and specifically recognizes the C-end DNA-binding domain of NPM1 C+, avoiding the nucleus-cytoplasm translocation involved in the AML tumorological process. The new NPM1 inhibitor triggers apoptosis in AML cell lines and primary cells from AML patients and reduces tumor infiltration in a mouse model of AML with NPM1 C+ mutation. The disclosed phenotype-guided discovery of UCM-13369, a novel small molecule inspired on microbiota metabolites, confirms that CSC death induced by NPM1 inhibition represents a promising therapeutic opportunity for NPM1-mutated AML, a high-mortality disease., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

More than 50 years have passed since Nobel laureate Cristian de Duve described for the first time the presence of tiny subcellular compartments filled with hydrolytic enzymes: the lysosome. For a long time, lysosomes were deemed simple waste bags exerting a plethora of hydrolytic activities involved in the recycling of biopolymers, and lysosomal genes were considered to just be simple housekeeping genes, transcribed in a constitutive fashion. However, lysosomes are emerging as multifunctional signalling hubs involved in multiple aspects of cell biology, both under homeostatic and pathological conditions. Lysosomes are involved in the regulation of cell metabolism through the mTOR/TFEB axis. They are also key players in the regulation and onset of the immune response. Furthermore, it is becoming clear that lysosomal hydrolases can regulate several biological processes outside of the lysosome. They are also implicated in a complex communication network among subcellular compartments that involves intimate organelle-to-organelle contacts. Furthermore, lysosomal dysfunction is nowadays accepted as the causative event behind several human pathologies: low frequency inherited diseases, cancer, or neurodegenerative, metabolic, inflammatory, and autoimmune diseases. Recent advances in our knowledge of the complex biology of lysosomes have established them as promising therapeutic targets for the treatment of different pathologies. Although recent discoveries have started to highlight that lysosomes are controlled by a complex web of regulatory networks, which in some cases seem to be cell- and stimuli-dependent, to harness the full potential of lysosomes as therapeutic targets, we need a deeper understanding of the little-known signalling pathways regulating this subcellular compartment and its functions., (© 2022 The Authors. FEBS Open Bio published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)