Noninvasive optical imaging of cysteine protease activity using fluorescently quenched activity-based probes

Abstract

We have generated a series of quenched near-infrared fluorescent activity-based probes (qNIRF-ABPs) that covalently target the papain-family cysteine proteases shown previously to be important in multiple stages of tumorigenesis. These 'smart' probes emit a fluorescent signal only after covalently modifying a specific protease target. After intravenous injection of NIRF-ABPs into mice bearing grafted tumors, noninvasive, whole-body imaging allowed direct monitoring of cathepsin activity. Importantly, the permanent nature of the probes also allowed secondary, ex vivo biochemical profiling to identify specific proteases and to correlate their activity with whole-body images. Finally, we demonstrate that these probes can be used to monitor small-molecule inhibition of protease targets both biochemically and by direct imaging methods. Thus, NIRF-ABPs are (i) potentially valuable new imaging agents for disease diagnosis and (ii) powerful tools for preclinical and clinical testing of small-molecule therapeutic agents in vivo.

Molecular mechanism of quinone signaling mediated through S-quinonization of a YodB family repressor QsrR

“…Cys-alkylation plays important roles in biology (52,53); however, Cys-alkylation by quinones in signaling and transcription has not been revealed in the past. Comparison of the structures of QsrR-DNA and QsrRmenadione indicates that menadione association causes the two QsrR monomers to rotate, leading to the dissociation of QsrR from operator DNA.…”

Activatable aptamer probe for contrast-enhanced in vivo cancer imaging based on cell membrane protein-triggered conformation alteration

“…In the context of molecular imaging, a variety of such probes have been developed (14)(15)(16)(17)(18)(19)(20)(21). Typical mechanisms include enzymatic cleavage of a quencher group from the fluorescence moiety using cancer-related enzymes (15)(16)(17)(18), intracellular degradation of fluorescence-quenched protein against cancer cell receptors (19,20), and surrounding-sensitized fluorescence labels conjugated to macromolecular ligands selectively endocytosed by cancer cells (8).…”

Optical imaging for the new grammar of drug discovery

“…Upregulation of cysteine cathepsin is associated with many diseases, including cancer, atherosclerosis, inflammation and Alzheimer's disease [47,48]. Bogyo and co-workers [47] reported the use of ABFPs for monitoring cathepsin activity in an in vivo tumour model.…”

“…Bogyo and co-workers [47] reported the use of ABFPs for monitoring cathepsin activity in an in vivo tumour model. The probes showed punctuate labelling of lysosomal compartments that overlapped with acidotropic lysosomal marker.…”