The first BODIPY library (BD) was synthesized, and a highly selective glucagon sensor, Glucagon Yellow (BD-105), was discovered by fluorescence image-based screening method. BD library was synthesized via a Knoevenagel-type condensation reaction with 160 benzaldehydes and the 1,3 dimethyl-BODIPY scaffold. Using BD compounds, a fluorescence image-based screening was performed against three cell lines including AlphaTC1 and BetaTC6 cells which secret glucagon and insulin, respectively, and HeLa as control cells. Out of the 160 candidate probes, one compound, Glucagon Yellow, exhibited selective staining only in AlphaTC1 cells. The selectivity of Glucagon Yellow toward glucagon was confirmed in vitro by comparison of its fluorescence intensity change against 19 biologically relevant analytes. Subsequent immunostaining experiments revealed that Glucagon Yellow and the glucagon antibody colocalized in pancreas tissue, showing a high quantitative correlation analysis by the Pearson's coefficient constant (R(r) = 0.950). These results demonstrated the potential application of Glucagon Yellow as a glucagon imaging agent in live cells and tissues.

Photoactivation of caged biomolecules has become a powerful approach to study cellular signalling events. Here we report a method for anchoring and uncaging biomolecules exclusively at the outer leaflet of the plasma membrane by employing a photocleavable, sulfonated coumarin derivative. The novel caging group allows quantifying the reaction progress and efficiency of uncaging reactions in a live-cell microscopy setup, thereby greatly improving the control of uncaging experiments. We synthesized arachidonic acid derivatives bearing the new negatively charged or a neutral, membrane-permeant coumarin caging group to locally induce signalling either at the plasma membrane or on internal membranes in β-cells and brain slices derived from C57B1/6 mice. Uncaging at the plasma membrane triggers a strong enhancement of calcium oscillations in β-cells and a pronounced potentiation of synaptic transmission while uncaging inside cells blocks calcium oscillations in β-cells and causes a more transient effect on neuronal transmission, respectively. The precise subcellular site of arachidonic acid release is therefore crucial for signalling outcome in two independent systems.

Chemical dimerizers are powerful tools for non-invasive manipulation of enzyme activities in intact cells. Here we introduce the first rapidly reversible small-molecule-based dimerization system and demonstrate a sufficiently fast switch-off to determine kinetics of lipid metabolizing enzymes in living cells. We applied this new method to induce and stop phosphatidylinositol 3-kinase (PI3K) activity, allowing us to quantitatively measure the turnover of phosphatidylinositol 3,4,5-trisphosphate (PIP3) and its downstream effectors by confocal fluorescence microscopy as well as standard biochemical methods.

No abstract

Caged compounds are designed to release biologically active signaling molecules with temporal, spatial, and even subcellular resolution. But how localized does the signal stay? Using the example of diacylglycerol, some signal responses (PKC) are shown to remain spatially distinct while other signals ([Ca2+]i) spread across the entire cell. Surprisingly, this distribution patterns depend on the fatty acid composition of the lipid species.