A fluorogenic chemically induced dimerization technology for controlling, imaging and sensing protein proximity.

Molecular tools enabling the control and observation of the proximity of proteins are essential for studying the functional role of physical distance between two proteins. Here we present CATCHFIRE (chemically assisted tethering of chimera by fluorogenic-induced recognition), a chemically induced proximity technology with intrinsic fluorescence imaging and sensing capabilities. CATCHFIRE relies on genetic fusion to small dimerizing domains that interact upon addition of fluorogenic inducers of proximity that fluoresce upon formation of the ternary assembly, allowing real-time monitoring of the chemically induced proximity. CATCHFIRE is rapid and fully reversible and allows the control and tracking of protein localization, protein trafficking, organelle transport and cellular processes, opening new avenues for studying or controlling biological processes with high spatiotemporal resolution. Its fluorogenic nature allows the design of a new class of biosensors for the study of processes such as signal transduction and apoptosis.

Adenosine plasma level in patients with paroxysmal or persistent atrial fibrillation and normal heart during ablation procedure and/or cardioversion.

The mechanism of atrial fibrillation (AF) in patients with normal heart remains unclear. While exogenous adenosine can trigger AF, nothing is known about the behavior of endogenous adenosine plasma level (APL) at the onset of AF and during ablation procedure. Ninety-one patients (68 with paroxysmal AF: 40 males, 66 ± 16 years; 23 with persistent AF: 14 males, 69 ± 11 years) and 18 controls were included. Among paroxysmal patients: i) medical therapy alone was performed in 45 cases and ablation procedure in 23. AF was spontaneously resolutive in 6 cases; ii) 23 underwent ablation procedure and blood was collected simultaneously in a brachial vein and in the left atrium; 17 were spontaneously in sinus rhythm while 6 were in sinus rhythm after direct current cardioversion. Among persistent patients: i) in 17 patients, blood samples were collected in a brachial vein before and after direct current cardioversion; ii) in 6 patients, blood samples were collected simultaneously in a brachial vein and in left atrium before and after cardioversion during ablation procedure. CV-APL was higher in patients with persistent AF vs patients with paroxysmal AF (median [range]: 0.9[0.6-1.1] vs 0.7[0.4-1.1] µM; p < 0.001). In patients with paroxysmal AF, LA-APL increased during the AF episode (0.95[0.85-1.4] vs 2.7[1.5-7] µM; p = 0.03) and normalized in sinus rhythm after DCCV. In patients with persistent AF, LA-APL was higher than CV-APL (1.2[0.7-1.8] vs 0.9[0.6-1.1] µM; p < 0.001), and both normalized in sinus rhythm (CV-APL: 0.8[0.6-1.1] vs 0.75[0.4-1] µM; p = 0.03), (LA-APL: 1.95[1.3-3] vs 1[0.5-1.15] µM; p = 0.03). The occurrence of AF is associated with a strong increase of APL in the atrium. The cause of this increase needs further investigations.

A Negative Allosteric Modulator of WNT Receptor Frizzled 4 Switches into an Allosteric Agonist.

The WNT pathway interconnects a network of signaling events involved in a huge plethora of cellular processes, from organogenesis to tissue homeostasis. Despite its importance, the exiguity of organic drugs directly targeting the members of the Frizzled family of WNT receptors has hampered progress across the whole spectrum of biological fields in which the signaling is involved. We here present FzM1.8, a small molecule acting as an allosteric agonist of Frizzled receptor FZD4. FzM1.8 derives from FzM1, a negative allosteric modulator of the receptor. Replacement of FzM1 thiophene with a carboxylic moiety induces a molecular switch in the lead and transforms the molecule into an activator of WNT signaling. We here show that, in the absence of any WNT ligand, FzM1.8 binds to FZD4, promotes recruitment of heterotrimeric G proteins, and biases WNT signaling toward a noncanonical route that involves PI3K. Finally, in colon cancer cells, we prove that the FZD4/PI3K axis elicited by FzM1.8 preserves stemness and promotes proliferation of undifferentiated cells.

Pharmacological folding chaperones act as allosteric ligands of Frizzled4.

Upon binding, ligands can chaperone their protein targets by preventing them from misfolding and aggregating. Thus, an organic molecule that works as folding chaperone for a protein might be its specific ligand, and, similarly, the chaperone potential could represent an alternative readout in a molecular screening campaign toward the identification of new hits. Here we show that small molecules selected for acting as pharmacological chaperones on a misfolded mutant of the Frizzled4 (Fz4) receptor bind and modulate wild-type Fz4, representing what are to our knowledge the first organic ligands of this until-now-undruggable GPCR. The novelty and the advantages of the screening platform, the allosteric binding site addressed by these new ligands and the mechanism they use to modulate Fz4 suggest new avenues for development of inhibitors of the Wnt-ß-catenin pathway and for drug discovery.

A fluorescent reporter system for anaerobic thermophiles.

Owing to their inherent capacity to make invisible biological processes visible and quantifiable, fluorescent reporter systems have numerous applications in biotechnology. For classical fluorescent protein systems (i.e., GFP and derivatives), chromophore maturation is O2-dependent, restricting their applications to aerobic organisms. In this work, we pioneered the use of the oxygen-independent system FAST (Fluorescence Activating and absorption Shifting tag) in the thermophilic anaerobe Thermoanaerobacter kivui. We developed a modular cloning system that was used to easily clone a library of FAST expression cassettes in an E. coli-Thermoanaerobacter shuttle plasmid. FAST-mediated fluorescence was then assessed in vivo in T. kivui, and we observed bright green and red fluorescence for cells grown at 55°C. Next, we took advantage of this functional reporter system to characterize a set of homologous and heterologous promoters by quantifying gene expression, expanding the T. kivui genetic toolbox. Low fluorescence at 66°C (Topt for T. kivui) was subsequently investigated at the single-cell level using flow cytometry and attributed to plasmid instability at higher temperatures. Adaptive laboratory evolution circumvented this issue and drastically enhanced fluorescence at 66°C. Whole plasmid sequencing revealed the evolved strain carried functional plasmids truncated at the Gram-positive origin of replication, that could however not be linked to the increased fluorescence displayed by the evolved strain. Collectively, our work demonstrates the applicability of the FAST fluorescent reporter systems to T. kivui, paving the way for further applications in thermophilic anaerobes.

K-Ras Binds Calmodulin-Related Centrin1 with Potential Implications for K-Ras Driven Cancer Cell Stemness.

Recent data suggest that K-Ras4B (hereafter K-Ras) can drive cancer cell stemness via calmodulin (CaM)-dependent, non-canonical Wnt-signalling. Here we examined whether another Ca2+-binding protein, the CaM-related centrin1, binds to K-Ras and could mediate some K-Ras functions that were previously ascribed to CaM. While CaM and centrin1 appear to distinguish between peptides that were derived from their classical targets, they both bind to K-Ras in cells. Cellular BRET- and immunoprecipitation data suggest that CaM engages more with K-Ras than centrin1 and that the interaction with the C-terminal membrane anchor of K-Ras is sufficient for this. Surprisingly, binding of neither K-Ras nor its membrane anchor alone to CaM or centrin1 is sensitive to inhibition of prenylation. In support of an involvement of the G-domain of K-Ras in cellular complexes with these Ca2+-binding proteins, we find that oncogenic K-RasG12V displays increased engagement with both CaM and centrin1. This is abrogated by addition of the D38A effector-site mutation, suggesting that K-RasG12V is held together with CaM or centrin1 in complexes with effectors. When treated with CaM inhibitors, the BRET-interaction of K-RasG12V with centrin1 was also disrupted in the low micromolar range, comparable to that with CaM. While CaM predominates in regulating functional membrane anchorage of K-Ras, it has a very similar co-distribution with centrin1 on mitotic organelles. Given these results, a significant overlap of the CaM- and centrin1-dependent functions of K-Ras is suggested.

A Boost in Mitochondrial Activity Underpins the Cholesterol-Lowering Effect of Annurca Apple Polyphenols on Hepatic Cells.

Reduction in cholesterol blood levels represents one of the therapeutic goals to achieve in order to reduce the occurrence of cardiovascular diseases. Commonly, this goal is attempted by promoting healthy lifestyle behaviors and low-fat diets. Recently, several nutraceuticals have been shown to possess cholesterol-lowering properties and are becoming common over the counter products. Among others, apple polyphenols efficiently lower total cholesterol levels in humans and impact overall lipid metabolism. Malus Pumila Miller cv Annurca is an apple native to Southern Italy presenting one of the highest content of procyanidin B2, a dimeric procyanidin. Tested in clinical trials, the oral consumption of an Annurca polyphenolic extract (AAE) exerted a cholesterol-lowering effect similar to the statins Atorvastatin and Simvastatin. Despite AAE activity, the analysis of the molecular mechanism behind its cholesterol-lowering effect is unclear. Using isotope labeling and high-resolution mass spectrometry approaches we here performed a metabolic profiling of in vitro cultured human hepatocytes treated with AAE to reveal its mechanism of action. The results show that AAE acts differently than statins. The extract reprograms hepatic cell metabolism and promotes mitochondrial respiration, lipolysis and fatty acid ß-oxidation. Citrate and acetyl-CoA, both necessary for the production of cholesterol, are diverted to the Krebs Cycle by AAE, that, ultimately, lowers cholesterogenesis and fatty acid synthesis.

Annurca Apple Polyphenols Ignite Keratin Production in Hair Follicles by Inhibiting the Pentose Phosphate Pathway and Amino Acid Oxidation.

Patterned hair loss (PHL) affects around 50% of the adult population worldwide. The negative impact that this condition exerts on people's life quality has boosted the appearance of over-the-counter products endowed with hair-promoting activity. Nutraceuticals enriched in polyphenols have been recently shown to promote hair growth and counteract PHL. Malus pumila Miller cv. Annurca is an apple native to Southern Italy presenting one of the highest contents of Procyanidin B2. We have recently shown that oral consumption of Annurca polyphenolic extracts (AAE) stimulates hair growth, hair number, hair weight and keratin content in healthy human subjects. Despite its activity, the analysis of the molecular mechanism behind its hair promoting effect is still partially unclear. In this work we performed an unprecedented metabolite analysis of hair follicles (HFs) in mice topically treated with AAE. The metabolomic profile, based on a high-resolution mass spectrometry approach, revealed that AAE re-programs murine HF metabolism. AAE acts by inhibiting several NADPH dependent reactions. Glutaminolysis, pentose phosphate pathway, glutathione, citrulline and nucleotide synthesis are all halted in vivo by the treatment of HFs with AAE. On the contrary, mitochondrial respiration, ß-oxidation and keratin production are stimulated by the treatment with AAE. The metabolic shift induced by AAE spares amino acids from being oxidized, ultimately keeping them available for keratin biosynthesis.

Annurca Apple Polyphenols Protect Murine Hair Follicles from Taxane Induced Dystrophy and Hijacks Polyunsaturated Fatty Acid Metabolism toward ß-Oxidation.

Chemotherapy-induced alopecia (CIA) is a common side effect of conventional chemotherapy and represents a major problem in clinical oncology. Even months after the end of chemotherapy, many cancer patients complain of hair loss, a condition that is psychologically difficult to manage. CIA disturbs social and sexual interactions and causes anxiety and depression. Synthetic drugs protecting from CIA and endowed with hair growth stimulatory properties are prescribed with caution by oncologists. Hormones, growth factors, morphogens could unwontedly protect tumour cells or induce cancer cell proliferation and are thus considered incompatible with many chemotherapy regimens. Nutraceuticals, on the contrary, have been shown to be safe and effective treatment options for hair loss. We here show that polyphenols from Malus Pumila Miller cv Annurca are endowed with hair growth promoting activity and can be considered a safe alternative to avoid CIA. In vitro, Annurca Apple Polyphenolic Extract (AAE) protects murine Hair Follicles (HF) from taxanes induced dystrophy. Moreover, in virtue of its mechanism of action, AAE is herein proven to be compatible with chemotherapy regimens. AAE forces HFs to produce ATP using mitochondrial ß-oxidation, reducing Pentose Phosphate Pathway (PPP) rate and nucleotides production. As consequence, DNA replication and mitosis are not stimulated, while a pool of free amino acids usually involved in catabolic reactions are spared for keratin production. Moreover, measuring the effect exerted on Poly Unsaturated Fatty Acid (PUFA) metabolism, we prove that AAE promotes hair-growth by increasing the intracellular levels of Prostaglandins F2α (PGF2α) and by hijacking PUFA catabolites toward ß-oxidation.

WNT Inhibitory Activity of Malus Pumila miller cv Annurca and Malus domestica cv Limoncella Apple Extracts on Human Colon-Rectal Cells Carrying Familial Adenomatous Polyposis Mutations.

Inhibitors of the Wingless-related Integration site (WNT)/ß-catenin pathway have recently been under consideration as potential chemopreventive agents against Familial Adenomatous Polyposis (FAP). This autosomal-dominant syndrome is caused by germline mutations in the gene coding for the protein APC and leads to hyperactivation of the WNT/ß-catenin signaling pathway, uncontrolled intestinal cell proliferation and formation of adenocarcinomas. The aim of the present work was to: (i) test, on in vitro cultures of cells carrying FAP mutations and on ex vivo biopsies of FAP patients, the WNT inhibitory activity of extracts from two common southern Italian apples, Malus pumila Miller cv. 'Annurca' and Malus domestica cv 'Limoncella'; (ii) identify the mechanisms underpinning their activities and; (iii) evaluate their potency upon gastrointestinal digestion. We here show that both Annurca and Limoncella apple extracts act as WNT inhibitors, mostly thanks to their polyphenolic contents. They inhibit the pathway in colon cells carrying FAP mutations with active dilutions falling in ranges close to consumer-relevant concentrations. Food-grade manufacturing of apple extracts increases their WNT inhibitory activity as result of the conversion of quercetin glycosides into the aglycone quercetin, a potent WNT inhibitor absent in the fresh fruit extract. However, in vitro simulated gastrointestinal digestion severely affected WNT inhibitory activity of apple extracts, as result of a loss of polyphenols. In conclusion, our results show that apple extracts inhibit the WNT pathway in colon cells carrying FAP mutations and represent a potential nutraceutical alternative for the treatment of this pathology. Enteric coating is advisable to preserve the activity of the extracts in the colon-rectal section of the digestive tract.