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Traditional Chinese Medicines (TCMs) have been historically used to treat bacterial infections. However, the molecules responsible for these anti-infective properties and their potential mechanisms of action have remained elusive. Using a high-throughput assay for type III protein secretion in Salmonella enterica serovar Typhimurium, we discovered that several TCMs can attenuate this key virulence pathway without affecting bacterial growth. Among the active TCMs, we discovered that baicalein, a specific flavonoid from Scutellaria baicalensis, targets S. Typhimurium pathogenicity island-1 (SPI-l) type III secretion system (T3SS) effectors and translocases to inhibit bacterial invasion of epithelial cells. Structurally related flavonoids present in other TCMs, such as quercetin, also inactivated the SPI-1 T3SS and attenuated S. Typhimurium invasion. Our results demonstrate that specific plant metabolites from TCMs can directly interfere with key bacterial virulence pathways and reveal a previously unappreciated mechanism of action for anti-infective medicinal plants. [ABSTRACT FROM AUTHOR]

Cation-π interactions have been proposed to be important contributors to protein structure and function. In particular, these interactions have been suggested to provide significant stability at the solventexposed surface of a protein. We have investigated the magnitude of cation-π interactions between phenylalanine (Phe) and lysine (Lys), ornithine (Orn), and diaminobutanoic acid (Dab) in the context of an α-helix and have found that only the Phe···Orn interaction provides significant stability to the helix, stabilizing it by -0.4 kcal/mol. This interaction energy is in the same range as a salt bridge in an α-helix, and equivalent to the recently reported Trp···Arg interaction in an α-helix, despite the fact that Trp···guanidinium interactions have been proposed to be stronger than Phe···ammonium interactions. These results indicate that even the simplest cation-π interaction can provide significant stability to protein structure and demonstrate the subtle factors that can influence the observed interaction energies in designed systems. [ABSTRACT FROM AUTHOR]

The article discusses the use of a carboxypeptidase G2 (CPG2)-based reporter system to detect the type III protein secretion from Gram-negative bacterial pathogens. Researchers synthesize a glutamate (Glu)-modified derivative of 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (CyFur) to be used as a fluorogenic substrate for CPG2 and explore the sensitivity of the CPG:Gu-CyFur reporter system. It is noted that this system can monitor protein expression and secretion with sensitivity.

Head and neck cancer is a major cancer type, with high motility rates that reduce the quality of life of patients. Herein, we investigated the effectiveness and mechanism of a combination therapy involving TLR9 activator (CpG-2722) and phosphatidylserine (PS)-targeting prodrug of SN38 (BPRDP056) in a syngeneic orthotopic head and neck cancer animal model. The results showed a cooperative antitumor effect of CpG-2722 and BPRDP056 owing to their distinct and complementary antitumor functions. CpG-2722 induced antitumor immune responses, including dendritic cell maturation, cytokine production, and immune cell accumulation in tumors, whereas BPRDP056 directly exerted cytotoxicity toward cancer cells. We also discovered a novel function and mechanism of TLR9 activation, which increased PS exposure on cancer cells, thereby attracting more BPRDP056 to the tumor site for cancer cell killing. Killed cells expose more PS in tumor for BPRDP056 targeting. Tumor antigens released from the dead cells were taken up by antigen-presenting cells, which enhanced the CpG-272-promoted T cell-mediated tumor-killing effect. These form a positive feed-forward antitumor effect between the actions of CpG-2722 and BPRDP056. Thus, the study findings suggest a novel strategy of utilizing the PS-inducing function of TLR9 agonists to develop combinational cancer treatments using PS-targeting drugs., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

The function of the CXCR4/CXCL12 axis accounts for many disease indications, including tissue/nerve regeneration, cancer metastasis, and inflammation. Blocking CXCR4 signaling with its antagonists may lead to moving out CXCR4 + cell types from bone marrow to peripheral circulation. We have discovered a novel series of pyrimidine-based CXCR4 antagonists, a representative (i.e., 16) of which was tolerated at a higher dose and showed better HSC-mobilizing ability at the maximal response dose relative to the approved drug 1 (AMD3100), and thus considered a potential drug candidate for PBSCT indication. Docking compound 16 into the X-ray crystal structure of CXCR4 receptor revealed that it adopted a spider-like conformation striding over both major and minor subpockets. This putative binding mode provides a new insight into CXCR4 receptor-ligand interactions for further structural modifications.

A series of zinc(II) dipicolylamine (ZnDPA)-based drug conjugates have been synthesized to probe the potential of phosphatidylserine (PS) as a new antigen for small molecule drug conjugate (SMDC) development. Using in vitro cytotoxicity and plasma stability studies, PS-binding assay, in vivo pharmacokinetic studies, and maximum tolerated dose profiles, we provided a roadmap and the key parameters required for the development of the ZnDPA based drug conjugate. In particular, conjugate 24 induced tumor regression in the COLO 205 xenograft model and exhibited a more potent antitumor effect with a 70% reduction of cytotoxic payload compared to that of the marketed irinotecan when dosed at the same regimen. In addition to the validation of PS as an effective pharmacodelivery target for SMDC, our work also provided the foundation that, if applicable, a variety of therapeutic agents could be conjugated in the same manner to treat other PS-associated diseases.

Series of N -substituted carbazole analogues bearing an indole ring were synthesized as anti-methicillin-resistant Staphylococcus aureus (MRSA) agents from a molecular hybridization approach. The representative compound 19 showed an MIC = 1 μg/mL against a panel of MRSA clinical isolates as it possessed comparable in vitro activities to that of vancomycin. Moreover, compound 19 also exhibited MIC = 1 μg/mL activities against a recent identified Z172 MRSA strain (vancomycin-intermediate and daptomycin-nonsusceptible phenotype) and the vancomycin-resistant Enterococcus faecalis (VRE) strain. In a mouse model with lethal infection of MRSA (4N216), a 75% survival rate was observed after a single dose of compound 19 was intravenously administered at 20 mg/kg. In light of their equipotent activities against different MRSA isolates and VRE strain, the data underscore the importance of designed hybrid series for the development of new N -substituted carbazoles as potential anti-MRSA agents.

Protein S-prenylation is a lipid modification that regulates membrane-protein and protein-protein interactions in cell signaling. Though sites of protein S-prenylation can be predicted based upon conserved C-terminal CaaX or CC/CXC motifs, biochemical detection of protein S-prenylation in cells is still challenging. Herein, we report an alkynyl-isoprenol chemical reporter (alk-FOH) as an efficient substrate for prenyltransferases in mammalian cells that enables sensitive detection of S-farnesylated and S-geranylgeranylated proteins using bioorthogonal ligation methods. Fluorescent detection alleviates the need to deplete cellular isoprenoids for biochemical analysis of S-prenylated proteins and enables robust characterization of S-prenylated proteins, such as effectors that are injected into host cells by bacterial pathogens. This alkynyl-prenylation reporter provides a sensitive tool for biochemical analysis and rapid profiling of prenylated proteins in cells.

Recent years have seen the rapid advancement of new therapeutic agents against hepatitis C virus (HCV) in response to the need for treatment that is unmet by interferon (IFN)-based therapies. Most antiviral drugs discovered to date are small molecules that modulate viral enzyme activities. In the search for highly selective protein-binding molecules capable of disrupting the viral life cycle, we have identified a class of anionic tetraphenylporphyrins as potent and specific inhibitors of the HCV replicons. Based on the structure-activity relationship studies reported herein, meso-tetrakis-(3,5-dicarboxy-4,4'-biphenyl) porphyrin was found to be the most potent inhibitor of HCV genotype 1b (Con1) replicon systems but was less effective against the genotype 2a (JFH-1) replicon. This compound induced a reduction of viral RNA and protein levels when acting in the low nanomolar range. Moreover, the compound could suppress replicon rebound in drug-treated cells and exhibited additive to synergistic effects when combined with protease inhibitor BILN 2061 or with IFN-alpha-2a. Our results demonstrate the potential use of tetracarboxyphenylporphyrins as potent anti-HCV agents.

Proteins in nature fold into native conformations in which combinations of peripherally projected aliphatic, aromatic and ionic functionalities direct a wide range of properties. Alpha-helices, one of the most common protein secondary structures, serve as important recognition regions on protein surfaces for numerous protein-protein, protein-DNA and protein-RNA interactions. These interactions are characterized by conserved structural features within the alpha-helical domain. Rational design of structural mimetics of these domains with synthetic small molecules has proven an effective means to modulate such protein functions. In this tutorial review we discuss strategies that utilize synthetic small-molecule antagonists to selectively target essential protein-protein interactions involved in certain diseases. We also evaluate some of the protein-protein interactions that have been or are potential targets for alpha-helix mimetics.