Synthesis of novel small-molecule fluorescently labeled probes for the in vitro imaging of KCa3.1 channels

摘要： In order to facilitate the in vitro visualization of KCa3.1 channel-expressing cells, novel small-molecule imaging probes were designed and developed. Senicapoc showing high affinity and excellent selectivity towards the KCa3.1 channels was selected as targeting component. Different BODIPY dyes (15 - 20) were synthesized and connected by a Cu-catalyzed azide alkyne [3+2]cycloaddition with propargyl ether derivative 8 of senicapoc yielding fluorescently labeled ligands 21 - 26 targeting KCa3.1 channels. The novel dimethylpyrrole-based imaging probes 25 and 26 allow staining of KCa3.1 ion channels in NSCLC cells following a simple, fast and efficient protocol. The specificity was shown by removing the punctate staining pattern by pre-incubation with senicapoc. The density of KCa3.1 channels detected with fluorescent probe 25 and by immunostaining was identical. The punctate structure of the labeled channels could be observed in living cells as well. Molecular modeling studies showed binding of the senicapoc targeting component towards the binding site within the ion channel and orientation of the linker with the dye along the inner surface of the ion channel.