β-Cells respond directly to the intracellular photochemical release of caged inositol pyrophosphate isomers with modulations of oscillations in cytosolic Ca2+.

Although myo-inositol pyrophosphates such as diphosphoinositol pentakisphosphate (InsP) are important in biology, little quantitative information is available regarding their presence in mammalian organisms owing to the technical difficulties associated with accurately detecting these materials in biological samples. We have developed an analytical method whereby InsP and its precursor inositol hexakisphosphate (InsP) are determined directly and sensitively using tandem mass spectrometry coupled with hydrophilic interaction liquid chromatography (HILIC). InsP and InsP peak symmetry is influenced greatly by the buffer salt composition and pH of the mobile phase used in HILIC analysis. The use of 300 mM ammonium carbonate (pH 10.5) as an aqueous mobile phase resolves InsP and InsP on a polymer-based amino HILIC column with minimal peak tailing. Method validation shows that InsP and InsP can be quantitated from 20-500 pmol with minimal intra-day/inter-day variance in peak area and retention time. The concentration of InsP in C57BL/6J mouse brain (40.68 ± 3.84 pmol/mg wet weight) is successfully determined. HILIC‒MS/MS analysis using HEK293 culture cells confirms previous observations that InsP is induced by NaF treatment and ectopic expression of InsPK2, a primary kinase for InsP synthesis. Furthermore, this analysis reveals the abundance of InsP (50.46 ± 18.57 pmol/10 cells) and scarcity of InsP in human blood cells. The results demonstrate that HILIC‒MS/MS analysis can quantitate endogenous InsP and InsP in mouse and human samples, and we expect that the method will contribute to further understanding of InsP functions in mammalian pathobiology.

Inositol pyrophosphates constitute a family of hyperphosphorylated signaling molecules involved in the regulation of glucose uptake and insulin sensitivity. While our understanding of the biological roles of inositol heptaphosphates (PP-InsP 5 ) has greatly improved, the functions of the inositol octaphosphates ((PP) 2 -InsP 4 ) have remained unclear. Here we present the synthesis of two enantiomeric cell-permeant and photocaged (PP) 2 -InsP 4 derivatives and apply them to study the functions in living β-cells. Photorelease of the naturally occurring isomer 1,5-(PP) 2 -InsP 4 led to an immediate and concentration-dependent reduction of intracellular calcium oscillations, while other caged inositol pyrophosphates (3,5-(PP) 2 -InsP 4 , 5-PP-InsP 5 , 1-PP-InsP 5 , 3-PP-InsP 5 ) showed no immediate effect. Furthermore, uncaging of 1,5-(PP) 2 -InsP 4 but not 3,5-(PP) 2 -InsP 4 induced translocation of the C2AB domain of granuphilin from the plasma membrane to the cytosol. Granuphilin is involved in membrane docking of secretory vesicles. This suggests that 1,5-(PP) 2 -InsP 4 impacts β-cell activity by regulating granule localization and/or priming and calcium signaling in concert.

Technical challenges have to date prevented a complete profiling of the levels of myo-inositol phosphates (InsPs) and pyrophosphates (PP-InsPs) in mammalian tissues. Here, we have deployed capillary electrophoresis mass spectrometry...

Due to the emergence of multidrug resistant bacteria, the development of new antibiotics is required. We introduce here asymmetrically modified positively charged bis­(methylpyridinium) anthracenes as a novel tunable scaffold, in which the two positive charges can be placed at a defined distance and angle. Our structure–activity relationship reveals that coupling the methylpyridiniums with alkynyl linkers to the central anthracene unit yields antibacterial compounds against a wide range of bacteria, including Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis. Also, different mycobacteria, such as Mycobacterium smegmatis and Mycobacterium tuberculosis, are efficiently targeted by these compounds. The antibacterial activity depends on the number of alkynyl linkers and consequently also on the distance of the positive charges in the rigid anthracene scaffold. Additionally, the formation of an anthracene endoperoxide further increases the antibacterial activity, likely due to the release of toxic singlet oxygen that converts the endoperoxide back to the antibacterial anthracene scaffold with half-lives of several hours.