WNK1 kinase and its partners Akt, SGK1 and NBC-family Na+/HCO3- cotransporters are potential therapeutic targets for glioblastoma stem-like cells linked to Bisacodyl signaling.

Glioblastoma is a highly heterogeneous brain tumor. The presence of cancer cells with stem-like and tumor initiation/propagation properties contributes to poor prognosis. Glioblastoma cancer stem-like cells (GSC) reside in hypoxic and acidic niches favoring cell quiescence and drug resistance. A high throughput screening recently identified the laxative Bisacodyl as a cytotoxic compound targeting quiescent GSC placed in acidic microenvironments. Bisacodyl activity requires its hydrolysis into DDPM, its pharmacologically active derivative. Bisacodyl was further shown to induce tumor shrinking and increase survival in in vivo glioblastoma models. Here we explored the cellular mechanism underlying Bisacodyl cytotoxic effects using quiescent GSC in an acidic microenvironment and GSC-derived 3D macro-spheres. These spheres mimic many aspects of glioblastoma tumors in vivo, including hypoxic/acidic areas containing quiescent cells. Phosphokinase protein arrays combined with pharmacological and genetic modulation of signaling pathways point to the WNK1 serine/threonine protein kinase as a mediator of Bisacodyl cytotoxic effect in both cell models. WNK1 partners including the Akt and SGK1 protein kinases and NBC-family Na+/HCO3- cotransporters were shown to participate in the compound's effect on GSC. Overall, our findings uncover novel potential therapeutic targets for combatting glioblastoma which is presently an incurable disease.

Rapid and scalable synthesis of innovative unnatural α,ß or γ-amino acids functionalized with tertiary amines on their side-chains.

We report a selective ruthenium catalyzed reduction of tertiary amides on the side chain of Fmoc-Gln-OtBu derivatives, leading to innovative unnatural α,ß or γ-amino acids functionalized with tertiary amines. Rapid and scalable, this process allowed us to build a library of basic unnatural amino acids at the gram-scale and directly usable for liquid- or solid-phase peptide synthesis. The diversity of available tertiary amines allows us to modulate the physicochemical properties of the resulting amino acids, such as basicity or hydrophobicity.

BODIPY-bridged push-pull chromophores for nonlinear optical applications.

A set of linear and dissymmetric BODIPY-bridged push-pull dyes are synthesized. The electron-donating substituents are anisole and dialkylanilino groups. The strongly electron-accepting moiety, a 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) group, is obtained by insertion of an electron-rich ethyne into tetracyanoethylene. A nonlinear push-pull system is developed with a donor at the 5-position of the BODIPY core and the acceptor at the 2-position. All dyes are fully characterized and their electrochemical, linear and nonlinear optical properties are discussed. The linear optical properties of dialkylamino compounds show strong solvatochromic behavior and undergo drastic changes upon protonation. The strong push-pull systems are non-fluorescent and the TCBD-BODIPY dyes show diverse photochemistry and electrochemistry, with several reversible reduction waves for the tetracyanobutadiene moiety. The hyperpolarizability µß of selected compounds is evaluated using the electric-field-induced second-harmonic generation technique. Two of the TCBD-BODIPY dyes show particularly high µß (1.907 µm) values of 2050 × 10(-48) and 5900 × 10(-48) esu. In addition, one of these dyes shows a high NLO contrast upon protonation-deprotonation of the donor residue.

Thioxanthone functionalized silver nanorods as smart photoinitiating assemblies to generate photopolymer/metal nano-objects.

Silver nanorods (AgNRs) with lengths in the 50-60 nm range were synthesized and functionalized with 2-(2-mercaptoethyl)thioxanthone (C2TX) to generate AgNR@C2TX nanoassemblies. When irradiated at 377 nm in the presence of a diacrylate monomer, these dispersed nanoassemblies initiate radical photopolymerization, indicating that the excited singlet to triplet intersystem crossing process of C2TX in the vicinity of AgNRs was favored while the fluorescence of C2TX was completely quenched at the surface of NRs. SEM and TEM images confirmed the formation of a AgNR-polymer nanocomposite and the homogeneous dispersion of AgNRs in the polymer film. Moreover, under specific experimental conditions allowing the spatial extent of the polymerization to be limited, polymer-capped AgNRs were obtained (polymer diameter of ca. 1 nm).

Water-soluble red-emitting distyryl-borondipyrromethene (BODIPY) dyes for biolabeling.

A series of water-soluble red-emitting distyryl-borondipyrromethene (BODIPY) dyes were designed and synthesized by using three complementary approaches aimed at introducing water-solubilizing groups on opposite faces of the fluorescent core to reduce or completely suppress self-aggregation. An additional carboxylic acid functional group was introduced at the pseudo-meso position of the BODIPY scaffold for conjugation to amine-containing biomolecules/biopolymers. The optical properties of these dyes were evaluated under simulated physiological conditions (i.e., phosphate-buffered saline (PBS), pH 7.5) or in pure water. The emission wavelength (λ(max)) of these labels was found in the 640-660 nm range with quantum yields from modest to unprecedentedly high values (4 to 38%). The bioconjugation of these distyryl-BODIPY dyes with bovine serum albumin (BSA) and the monoclonal antibody (mAb) 12A5 was successfully performed under mild aqueous conditions.

Benzophenone-containing fatty acids and their related photosensitive fluorescent new probes: design, physico-chemical properties and preliminary functional investigations.

Hydrophobic photoaffinity labeling is a powerful strategy to identify hydrophobic segments within molecules, in particular membrane proteins. Here we report the design and synthesis of a novel family of fluorescent and photosensitive lipid tools, which have a common amino acid scaffold functionalized by three groups: (i) a first fatty acid chain grafted with a photoactivatable benzophenone moiety (Fatty Acid BenzoPhenone, FABP), (ii) a second fatty acid chain to ensure anchoring into a half-bilayer or hydrophobic environment, and (iii) a fluorescent carboxytetramethylrhodamine headgroup (CTMR) to detect the photolabeled compound. We present data of the synthesis and characterization of three lipid tools whose benzophenone ring is situated at various distances from the central scaffold. We could therefore establish structure/properties relationships dependent upon the depth of insertion of benzophenone into the membrane. Our lipid tools were extensively characterized both physico- and bio-chemically, and we assessed their functionality in vitro using bacterioRhodopsin (bR). We thus provide the scientific community with novel and reliable tools for the identification and study of hydrophobic regions in proteins.

Regioselective synthesis of 5-monostyryl and 2-tetracyanobutadiene BODIPY dyes.

Several unsymmetrically 2,5-disubstituted BODIPY dyes were obtained from 2-substituted derivatives (iodo, ethynylaryl) using a regioselective Knoevenagel condensation reaction with dimethylaminobenzaldehyde. The unsaturated, unsymmetrical 2-ethynyl-5-styryl-BODIPY undergoes a regioselective [2 + 2] cycloaddition reaction with tetracyanoethylene leading to the 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivative. This shows rich redox activity with two reversible oxidation and three reversible reduction waves at +0.72 V, +1.04 V; -0.32 V, -0.78 V, and -1.50 V, respectively.