pH driven fibrillar aggregation of the super-sweet protein Y65R-MNEI: A step-by-step structural analysis.

BACKGROUND: MNEI and its variant Y65R-MNEI are sweet proteins with potential applications as sweeteners in food industry. Also, they are often used as model systems for folding and aggregation studies. METHODS: X-ray crystallography was used to structurally characterize Y65R-MNEI at five different pHs, while circular dichroism and fluorescence spectroscopy were used to study their thermal and chemical stability. ThT assay and AFM were used for studying the kinetics of aggregation and morphology of the aggregates. RESULTS: Crystal structures of Y65R-MNEI revealed the existence of a dimer in the asymmetric unit, which, depending on the pH, assumes either an open or a closed conformation. The pH dramatically affects kinetics of formation and morphology of the aggregates: both MNEI and Y65R-MNEI form fibrils at acidic pH while amorphous aggregates are observed at neutral pH. CONCLUSIONS: The mutation Y65R induces structural modifications at the C-terminal region of the protein, which account for the decreased stability of the mutant when compared to MNEI. Furthermore, the pH-dependent conformation of the Y65R-MNEI dimer may explain the different type of aggregates formed as a function of pH. GENERAL SIGNIFICANCE: The investigation of the structural bases of aggregation gets us closer to the possibility of controlling such process, either by tuning the physicochemical environmental parameters or by site directed mutagenesis. This knowledge is helpful to expand the range of stability of proteins with potential industrial applications, such as MNEI and its mutant Y65R-MNEI, which should ideally preserve their structure and soluble state through a wide array of conditions.

An evaluation of Italian medical students attitudes and knowledge regarding forensic medicine.

INTRODUCTION: This study aims to assess students' knowledge of forensic medicine concepts and their opinions regarding the course taught during the degree course in Medicine and Surgery in an Italian university. Consequently, the study aims to assess the impact of the course on the students' knowledge and attitude in choosing a medical residency. MATERIALS AND METHODS: A cross-sectional study was conducted through an anonymous web-based survey of medical students at the Università Cattolica del Sacro Cuore. Descriptive and univariate analysis were conducted. RESULTS: 1166 students completed the survey. The forensic medicine course appears to be extremely important in providing training in the fundamental concepts of forensic medicine, especially professional liability, defensive medicine, and forensic pathology. Attending autopsies is important during the course, and their number should be more than ten. Additionally, univariate analysis demonstrates that students' awareness of forensic medicine topics, such as the function of the forensic physicians, professional liability, and defensive medicine, improves in the fifth or sixth year of the course. After the course, more students would choose to pursue a nonclinical and nonsurgical specialty, and forensic medicine specifically, for their residency. CONCLUSIONS: The forensic medicine course has the task of defining the duties and responsibilities of forensic physicians, providing indispensable tools for future medical practitioners, regardless of their future specialisation, and limiting the increasing use of defensive medicine. In conclusion, we recommend further multicenter studies to evaluate the role and direct effect of undergraduate forensic medicine courses on students and on the quality of practice.

Child maltreatment and management of pediatric patients during COVID-19 pandemic: Knowledge, awareness, and attitudes among students of medicine and surgery. A survey-based analysis.

Purpose of the study: To assess perception, awareness, and attitudes regarding the medico-legal relevance of child maltreatment and management of pediatric patients during the COVID-19 pandemic in a cohort of medicine and surgery students, with a particular focus on child safety and maltreatment. Methods: A cross-sectional, web-based survey was conducted through an anonymous questionnaire on the personal websites of Università Cattolica del Sacro Cuore medical students. Results: The study included 1,166 participants, the majority of whom were experienced with child maltreatment and defensive medicine; only a small percentage was aware of the government's efforts to prevent child maltreatment and safeguard vaccination physicians. Moreover, there was no agreement on the use of telemedicine for non-serious pediatric patients or on the consequences it might have on their health. Finally, the detrimental impacts of lockdown on children's mental health are a major worry. Conclusions: Knowledge of these themes is mainly implemented by deepening these concepts during the undergraduate studies since a high level of knowledge on child maltreatment and on the management of COVID-19 pandemic was significantly associated with clinical years of course. Specific seminars analyzing telemedicine and legislative protections concerning minors and those concerning vaccination doctors should be included in the study plan to raise awareness these concepts.

Apogossypol derivatives as antagonists of antiapoptotic Bcl-2 family proteins.

Guided by a combination of nuclear magnetic resonance binding assays and computational docking studies, we synthesized a library of 5,5' substituted Apogossypol derivatives as potent Bcl-XL antagonists. Each compound was subsequently tested for its ability to inhibit Bcl-XL in an in vitro fluorescence polarization competition assay and exert single-agent proapoptotic activity in human cancer cell lines. The most potent compound BI79D10 binds to Bcl-XL, Bcl-2, and Mcl-1 with IC50 values of 190, 360, and 520 nmol/L, respectively, and potently inhibits cell growth in the H460 human lung cancer cell line with an EC50 value of 680 nmol/L, expressing high levels of Bcl-2. BI79D10 also effectively induces apoptosis of the RS11846 human lymphoma cell line in a dose-dependent manner and shows little cytotoxicity against bax-/-bak-/- mouse embryonic fibroblast cells, in which antiapoptotic Bcl-2 family proteins lack a cytoprotective phenotype, implying that BI79D10 has little off-target effects. BI79D10 displays in vivo efficacy in transgenic mice, in which Bcl-2 is overexpressed in splenic B cells. Together with its improved plasma and microsomal stability relative to Apogossypol, BI79D10 represents a lead compound for the development of novel apoptosis-based therapies for cancer.

Development of paramagnetic probes for molecular recognition studies in protein kinases.

We report on the synthesis and evaluation of an indazole-spin-labeled compound that was designed as an effective chemical probe for second site screening against the protein kinase JNK using NMR-based techniques. We demonstrate the utility of the derived compound in detecting and characterizing binding events at the protein kinase docking site. In addition, we report on the NMR-based design and synthesis of a bidentate compound spanning both the ATP site and the docking site. We show that the resulting compound has nanomolar affinity for JNK despite the relatively weak affinities of the individual fragments that constitute it. The approach demonstrates that targeting the docking site of protein kinases represents a valuable yet unexplored avenue to obtain potent kinase inhibitors with increased selectivity.

Ecotoxicological survey of MNEI and Y65R-MNEI proteins as new potential high-intensity sweeteners.

Low-calorie sweeteners are widespread. They are routinely introduced into commonly consumed food such as diet sodas, cereals, and sugar-free desserts. Recent data revealed the presence in considerable quantities of some of these artificial sweeteners in water samples qualifying them as a class of potential new emerging contaminants. This study aimed at evaluating the ecotoxicity profile of MNEI and Y65R-MNEI, two engineered products derived from the natural protein monellin, employing representative test organism such as Daphnia magna, Ceriodaphnia dubia, and Raphidocelis subcapitata. Potential genotoxicity and mutagenicity effects on Salmonella typhimurium (strain TA97a, TA98, TA100, and TA1535) and Escherichia coli (strain WP2 pkM101) were evaluated. No genotoxicity effects were detected, whereas slight mutagenicity was highlighted by TA98 S. typhimurium. Ecotoxicity results evidenced effects approximately up to 14 and 20% with microalgae at 500 mg/L of MNEI and Y65R-MNEI, in that order. Macrophytes and crustaceans showed no significant effects. No median effective concentrations were determined. Overall, MNEI and Y65R-MNEI can be classified as not acutely toxic for the environment.

A preliminary study on the application of natural sweet proteins in agar-based gels.

Natural sweet proteins may be used as sugar replacer in simple liquid food systems but their applicability in more complex matrices has not been investigated yet. Gelling agent nature and texture characteristics as well as type and distribution of a stimulus in a gel could affect taste perception through inhibition or enhancement of tastants migration to the receptors. The mechanical, nonoral texture and time-intensity sweetness characteristics of sweet proteins MNEI and super sweet Y65R mutant, aspartame and saccharin added at a concentration iso-sweet to 40 g/L of sucrose in three agar gel concentrations (1%, 1.5%, and 2%) were evaluated. The results have shown that agar concentration and agar sweetener interaction particularly affect mechanical fracture stress and non oral hardness of the sweetened gels. Time intensity results illustrated that unlike in solution, the intensity of sweet taste in a gelled system over time decreases. Indeed, the behavior of the sweet proteins differed greatly in the gelled system compared to when they are in solution. PRACTICAL APPLICATIONS: MNEI has been proved to be a high-potency sweetener for beverages, but the possibility to use it in semisolid foodstuff was not investigated yet. This study represented a preliminary characterization of two variants of natural sweetener monellin, MNEI and Y65R in semisolid model foodstuff. The data were an important scientific contribution to the knowledge of sweet proteins in agar-based gels and could be useful in order to extend the possible application of these sweet proteins as low calorie sweeteners in semisolid foodstuffs. Some problems concerning their delivered sweetness in agar gels were underlined and their application should be optimized in order to improve sweetness conveyed.

Influence of pH on the structure and stability of the sweet protein MNEI.

MNEI is a single-chain derivative of the sweet protein monellin that, in recent years, has become an accepted model for studying protein dynamic properties such as folding and aggregation. Although MNEI is very resistant at acidic pH, exposure to neutral or alkaline pH strongly affects its stability. We have performed a thorough NMR study of the dynamic properties of MNEI at different pHs. The results demonstrate that, at physiological temperature, exposure to higher pH increases MNEI flexibility. The changes, originating from a well-defined region in the protein, are transmitted to the whole structure and are likely to be the key for triggering unfolding processes.

Design of sweet protein based sweeteners: hints from structure-function relationships.

Sweet proteins represent a class of natural molecules, which are extremely interesting regarding their potential use as safe low-calories sweeteners for individuals who need to control sugar intake, such as obese or diabetic subjects. Punctual mutations of amino acid residues of MNEI, a single chain derivative of the natural sweet protein monellin, allow the modulation of its taste. In this study we present a structural and functional comparison between MNEI and a sweeter mutant Y65R, containing an extra positive charge on the protein surface, in conditions mimicking those of typical beverages. Y65R exhibits superior sweetness in all the experimental conditions tested, has a better solubility at mild acidic pH and preserves a significant thermal stability in a wide range of pH conditions, although slightly lower than MNEI. Our findings confirm the advantages of structure-guided protein engineering to design improved low-calorie sweeteners and excipients for food and pharmaceutical preparations.

Mice lacking GD3 synthase display morphological abnormalities in the sciatic nerve and neuronal disturbances during peripheral nerve regeneration.

The ganglioside 9-O-acetyl GD3 is overexpressed in peripheral nerves after lesioning, and its expression is correlated with axonal degeneration and regeneration in adult rodents. However, the biological roles of this ganglioside during the regenerative process are unclear. We used mice lacking GD3 synthase (Siat3a KO), an enzyme that converts GM3 to GD3, which can be further converted to 9-O-acetyl GD3. Morphological analyses of longitudinal and transverse sections of the sciatic nerve revealed significant differences in the transverse area and nerve thickness. The number of axons and the levels of myelin basic protein were significantly reduced in adult KO mice compared to wild-type (WT) mice. The G-ratio was increased in KO mice compared to WT mice based on quantification of thin transverse sections stained with toluidine blue. We found that neurite outgrowth was significantly reduced in the absence of GD3. However, addition of exogenous GD3 led to neurite growth after 3 days, similar to that in WT mice. To evaluate fiber regeneration after nerve lesioning, we compared the regenerated distance from the lesion site and found that this distance was one-fourth the length in KO mice compared to WT mice. KO mice in which GD3 was administered showed markedly improved regeneration compared to the control KO mice. In summary, we suggest that 9-O-acetyl GD3 plays biological roles in neuron-glia interactions, facilitating axonal growth and myelination induced by Schwann cells. Moreover, exogenous GD3 can be converted to 9-O-acetyl GD3 in mice lacking GD3 synthase, improving regeneration.

SAR by interligand nuclear overhauser effects (ILOEs) based discovery of acylsulfonamide compounds active against Bcl-x(L) and Mcl-1.

Overexpression of antiapoptotic members of the Bcl-2 family proteins, such as Bcl-x(L) and Mfl-1, has been shown to be involved in resistance to chemotherapeutic drugs in many forms of cancers. Recent efforts from the Abbott Laboratories resulted in the development of the acylsulfonamide compound and clinical candidate that targets selectively Bcl-2, Bcl-x(L), and Bcl-w while it is not active against Mcl-1 and Bfl-1. However, early clinical and preclinical studies suggest that pan-Bcl-2 antagonists, targeting simultaneously Mcl-1, Bcl-xL, and possibly all other four antiapoptotic Bcl-2 proteins, may result in more efficacious drugs. Here, following an NMR fragment-based approach, SAR by ILOEs, we report on compounds that exhibit nanomolar affinities for both Bcl-x(L) and Mcl-1 in vitro. We believe that these molecules can be used as useful starting point for the development of novel Bcl-2 antagonists, in particular targeting Mcl-1.

An optically pure apogossypolone derivative as potent pan-active inhibitor of anti-apoptotic bcl-2 family proteins.

Our focus in the past several years has been on the identification of novel and effective pan-Bcl-2 antagonists. We have recently reported a series of Apogossypolone (ApoG2) derivatives, resulting in the chiral compound (±) BI97D6. We report here the synthesis and evaluation on its optically pure (-) and (+) atropisomers. Compound (-) BI97D6 potently inhibits the binding of BH3 peptides to Bcl-X(L), Bcl-2, Mcl-1, and Bfl-1 with IC(50) values of 76 ± 5, 31 ± 2, 25 ± 8, and 122 ± 28 nM, respectively. In a cellular assay, compound (-) BI97D6 effectively inhibits cell growth in the PC-3 human prostate cancer and H23 human lung cancer cell lines with EC(50) values of 0.22 ± 0.08 and 0.14 ± 0.02 µM, respectively. Similarly, compound (-) BI97D6 effectively induces apoptosis in the BP3 human lymphoma cell line in a dose-dependent manner. The compound also shows little cytotoxicity against bax(-/-)/bak(-/-) cells, suggesting that it kills cancers cells predominantly via a Bcl-2 pathway. Moreover, compound (-) BI97D6 displays in vivo efficacy in both a Bcl-2-transgenic mouse model and in a prostate cancer xenograft model in mice. Therefore, compound (-) BI97D6 represents a promising drug lead for the development of novel apoptosis-based therapies for cancer.

BI-97C1, an optically pure Apogossypol derivative as pan-active inhibitor of antiapoptotic B-cell lymphoma/leukemia-2 (Bcl-2) family proteins.

In our continued attempts to identify novel and effective pan-Bcl-2 antagonists, we have recently reported a series of compound 2 (Apogossypol) derivatives, resulting in the chiral compound 4 (8r). We report here the synthesis and evaluation on its optically pure individual isomers. Compound 11 (BI-97C1), the most potent diastereoisomer of compound 4, inhibits the binding of BH3 peptides to Bcl-X(L), Bcl-2, Mcl-1, and Bfl-1 with IC(50) values of 0.31, 0.32, 0.20, and 0.62 microM, respectively. The compound also potently inhibits cell growth of human prostate cancer, lung cancer, and lymphoma cell lines with EC(50) values of 0.13, 0.56, and 0.049 microM, respectively, and shows little cytotoxicity against bax(-/-)bak(-/-) cells. Compound 11 displays in vivo efficacy in transgenic mice models and also demonstrated superior single-agent antitumor efficacy in a prostate cancer mouse xenograft model. Therefore, compound 11 represents a potential drug lead for the development of novel apoptosis-based therapies against cancer.

Synthesis and biological evaluation of Apogossypolone derivatives as pan-active inhibitors of antiapoptotic B-cell lymphoma/leukemia-2 (Bcl-2) family proteins.

Overexpression of antiapoptotic Bcl-2 family proteins is commonly related with tumor maintenance, progression, and chemoresistance. Inhibition of these antiapoptotic proteins is an attractive approach for cancer therapy. Guided by nuclear magnetic resonance (NMR) binding assays, a series of 5,5' substituted compound 6a (Apogossypolone) derivatives was synthesized and identified pan-active antagonists of antiapoptotic Bcl-2 family proteins, with binding potency in the low micromolar to nanomolar range. Compound 6f inhibits the binding of BH3 peptides to Bcl-X(L), Bcl-2, and Mcl-1 with IC(50) values of 3.10, 3.12, and 2.05 µM, respectively. In a cellular assay, 6f potently inhibits cell growth in several human cancer cell lines in a dose-dependent manner. Compound 6f further displays in vivo efficacy in transgenic mice and demonstrated superior single-agent antitumor efficacy in a PPC-1 mouse xenograft model. Together with its negligible toxicity, compound 6f represents a promising drug lead for the development of novel apoptosis-based therapies for cancer.

Discovery and binding studies on a series of novel Pin1 ligands.

Pin1 plays a key role in various biological cellular processes via the recognition of phosphorylated Ser/Thr-Proline motifs. Moreover, high expression levels of Pin1 are correlated to tumorgenesis in some cancer types. Here, we identify a novel series of small molecular weight compounds with a core structure mimicking the phoshorylated serine. The binding affinity and binding mode of the compounds for Pin1 are analyzed via NMR spectroscopy and computational studies. The reported chemical probes and relative binding data to Pin1 represent valuable stepping stones for the validation of Pin1 as target for drug discovery and for eventually the development of possible lead compounds.

Identification of lead compounds as antagonists of protein Bcl-xL with a diversity-oriented multidisciplinary approach.

We report on the use of a diversity oriented synthesis (DOS) approach that resulted in the generation of a set of libraries of compounds presenting novel structural cores. These chemical cores have been employed to design potential antagonists of the antiapoptotic protein Bcl-x(L) through reiterated steps of molecular docking calculations followed by experimental verification of binding. Our data suggest that the DOS approach is suitable to generate novel scaffolds, which can be employed to target protein-protein interactions.

Synthesis and evaluation of Apogossypol atropisomers as potential Bcl-xL antagonists.

Anti-apoptotic Bcl-2 family proteins such as Bcl-2 and Bcl-X(L) have been recently validated as targets for the discovery of novel anti-cancer agents. We previously reported that racemic (+/-) Apogossypol, a semi-synthetic compound derived from the natural product Gossypol, binds and inhibits Bcl-2 and Bcl-X(L)in vitro and in cell. Given that (+) and (-) Gossypol display different proapoptotic activities, here we report on the synthesis of (+) and (-) Apogossypol and the evaluation of their in vitro and cellular activity.

Engineering a leucine zipper-TRAIL homotrimer with improved cytotoxicity in tumor cells.

Successful cancer therapies aim to induce selective apoptosis in neoplastic cells. The current suboptimal efficiency and selectivity drugs have therapeutic limitations and induce concomitant side effects. Recently, novel cancer therapies based on the use of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) have emerged. TRAIL, a key component of the natural antitumor immune response, selectively kills many tumor cell types. Earlier studies with recombinant TRAIL, however, revealed its many shortcomings including a short half-life, off-target toxicity, and existence of TRAIL-resistant tumor cells. We improved the efficacy of recombinant TRAIL by redesigning its structure and the expression and purification procedures. The result is a highly stable leucine zipper (LZ)-TRAIL chimera that is simple to produce and purify. This chimera functions as a trimer in a manner that is similar to natural TRAIL. The formulation of the recombinant LZ-TRAIL we have developed has displayed high specific activity in both cell-based assays in vitro and animal tests in vivo. Our results have shown that the half-life of LZ-TRAIL is improved and now exceeds 1 h in mice compared with a half-life of only minutes reported earlier for recombinant TRAIL. We have concluded that our LZ-TRAIL construct will serve as a foundation for a new generation of fully human LZ-TRAIL proteins suitable for use in preclinical and clinical studies and for effective combination therapies to overcome tumor resistance to TRAIL.

Apogossypol derivatives as pan-active inhibitors of antiapoptotic B-cell lymphoma/leukemia-2 (Bcl-2) family proteins.

Guided by nuclear magnetic resonance (NMR) binding assays and computational docking studies, a series of 5,5' substituted apogossypol derivatives was synthesized that resulted in potent pan-active inhibitors of antiapoptotic Bcl-2 family proteins. Compound 8r inhibits the binding of BH3 peptides to Bcl-X(L), Bcl-2, Mcl-1, and Bfl-1 with IC(50) values of 0.76, 0.32, 0.28, and 0.73 microM, respectively. The compound also potently inhibits cell growth of human lung cancer and BP3 human B-cell lymphoma cell lines with EC(50) values of 0.33 and 0.66 microM, respectively. Compound 8r shows little cytotoxicity against bax(-/-)bak(-/-) cells, indicating that it kills cancers cells via the intended mechanism. The compound also displays in vivo efficacy in transgenic mice in which Bcl-2 is overexpressed in splenic B-cells. Together with its improved chemical, plasma, and microsomal stability relative to compound 2 (apogossypol), compound 8r represents a promising drug lead for the development of novel apoptosis-based therapies for cancer.

Robust lanthanide-based assays for the detection of anti-apoptotic Bcl-2-family protein antagonists.

Anti-apoptotic Bcl-2-family proteins (Bcl-2, Bcl-x(L), Bfl-1, Mcl-1, Bcl-W and Bcl-B) have been recently validated as drug discovery targets for cancer, owed to their ability to confer tumor resistance to chemotherapy or radiation. The anti-apoptotic activity of Bcl-2 proteins is due to their ability to heterodimerize with their pro-apoptotic counterparts (proteins such as Bad, Bim or Bid) via a conserved peptide region termed BH3. Thus, molecules that mimic pro-apoptotic BH3 domains represent a direct approach to overcoming the protective effects of anti-apoptotic proteins such as Bcl-2 and Bcl-x(L). Here, we report on the development and evaluation of two novel Lanthanide-based assays that are formatted for high-throughput screening of small molecules capable of antagonizing BH3-Bcl-2 interactions. The assay conditions, robustness and reproducibility (Z' factors) are described. These assays represent useful tools to enable further studies in the search for novel, safe and effective anti-cancer agents targeting Bcl-2-family proteins.