A “Caged” Luciferin for Imaging Cell–Cell Contacts

Abstract

Cell-cell interactions underlie fundamental biological processes but remain difficult to visualize over long times and large distances in tissues and live organisms. Bioluminescence imaging with luciferase-luciferin pairs is sufficiently sensitive to image cells in vivo but lacks the spatial resolution to identify cellular locations and interactions. To repurpose this technology for visualizing cellular networks, we developed a "caged" luciferin that produces light only when cells are in close contact. This molecule comprises a nitroaromatic core that can be selectively reduced ("uncaged") by one cell type, liberating a luciferin that can be selectively consumed by neighboring, luciferase-expressing cells. When the two cell types are in contact, robust light emission is observed. This imaging strategy will enable the noninvasive visualization of cell-cell interactions relevant to organismal biology.

In vivo bioluminescence imaging reveals copper deficiency in a murine model of nonalcoholic fatty liver disease

“…Moreover, impressive advances in luciferase engineering and ease of targeting by genetic encoding permit the broad use of such reporters for in vivo imaging with cell and tissue specificity (41,43,44). We and others have developed caged luciferins, which are enzymeinert luciferin derivatives that are chemically unmasked to the luciferin substrate in the presence of an analyte or biochemical event of interest for subsequent enzymatic generation of light (45)(46)(47)(48)(49)(50); in particular, our laboratory has used this approach to develop bioluminescent H 2 O 2 reporters (45,47). To create a Cu + -responsive luciferin probe, we exploited a Cu + -dependent oxidative cleavage reaction mediated by the tetradentate ligand TPA (Fig.…”

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection

“…Work from our laboratory and others has demonstrated the utility of caged luciferins in vivo (28)(29)(30) for measuring transient small molecules (31)(32)(33)(34), enzyme and transporter activities (34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46), protein-protein and cell-cell interactions (42,47,48), and copper (49). Indeed, previous work from our laboratory utilized a Cu-dependent oxidation reaction to uncage luciferin for in vivo copper imaging (50), a first demonstration of a general activitybased sensing (ABS) strategy which we envisioned expanding to other essential metals in biology by changing the reaction trigger.…”

Economical and scalable synthesis of 6-amino-2-cyanobenzothiazole

“…In our hands, the use of iron powder in acetic acid proved more practical than the previously reported procedures with zinc powder and ammonium chloride [7]. It resulted in more consistent yields, an easier work-up, and no persistent contamination of 8 with nitroso intermediates [6]. The reduction step was accomplished on a 1 g and 5 g scale isolating ACBT 8 by filtration through a short silica plug to give the desired product in 60–71% yield.…”

“…Prescher and co-workers reported an alternative synthesis of ACBT that avoids the use of cyanide (Scheme 2) [7]. This route makes use of 4,5-dichloro-1,2,3-dithiazolium chloride (Appel’s salt, 12 ), and variations of the procedure have enabled the synthesis of different CBT derivatives, some of which on multi-gram scale [6–7 16–17]. However, Appel’s salt is relatively expensive and available from a limited number of suppliers, and its synthesis requires the use of the highly toxic reagent sulfur monochloride [18].…”