Bioluminescent imaging (BLI) has been widely applicable in the imaging of process envisioned in life sciences. As the most conventional technique for BLI, the firefly luciferin–luciferase system is exceptionally functional in vitro and in vivo. The state-of-the-art strategy in such a system is to cage the luciferin, in which free luciferin is conjugated with distinctive functional groups, thus accommodating an impressive toolkit for exploring various biological processes, such as monitoring enzymes activity, detecting bioactive small molecules, evaluating the properties of molecular transporters, etc. This review article summarizes the rational design of caged luciferins towards diverse biotargets, as well as their applications in bioluminescent imaging. It should be emphasized that these caged luciferins can stretch out the applications of bioluminescence imaging and shed light upon understanding the pathogenesis of various diseases.

Store-operated Ca²⁺ entry mediated by STIM1 and ORAI1 constitutes one of the major Ca²⁺ entry routes in mammalian cells. The molecular choreography of STIM1–ORAI1 coupling is initiated by endoplasmic reticulum (ER) Ca²⁺ store depletion with subsequent oligomerization of the STIM1 ER-luminal domain, followed by its redistribution towards the plasma membrane to gate ORAI1 channels. The mechanistic underpinnings of this inside-out Ca²⁺ signalling were largely undefined. By taking advantage of a unique gain-of-function mutation within the STIM1 transmembrane domain (STIM1-TM), here we show that local rearrangement, rather than alteration in the oligomeric state of STIM1-TM, prompts conformational changes in the cytosolic juxtamembrane coiled-coil region. Importantly, we further identify critical residues within the cytoplasmic domain of STIM1 (STIM1-CT) that entail autoinhibition. On the basis of these findings, we propose a model in which STIM1-TM reorganization switches STIM1-CT into an extended conformation, thereby projecting the ORAI-activating domain to gate ORAI1 channels.