An Activity-Based Probe for Cathepsin K Imaging with Excellent Potency and Selectivity

Area of Science:

• Biochemistry
• Molecular Biology
• Medicinal Chemistry

Background:

• Cathepsin K is a cysteine protease crucial for bone matrix degradation and implicated in bone diseases.
• Targeting cathepsin K offers a therapeutic strategy for conditions characterized by high bone turnover.

Purpose of the Study:

• To design and synthesize novel fluorescent activity-based probes (ABPs) for cathepsin K.
• To characterize the binding and inhibitory properties of these probes.
• To evaluate their utility in detecting and visualizing cathepsin K in biological systems.

Main Methods:

• Design and synthesis of fluorescent ABPs and their precursors.
• Biochemical assays to determine probe potency (k_inac/K_i) and selectivity.
• X-ray crystallography to elucidate the binding mode of probes with cathepsin K.
• Cell-based assays including live cell imaging of human osteosarcoma cells.

Main Results:

• ABP 25 demonstrated high potency and selectivity for human cathepsin K.
• Crystal structures revealed the binding interactions of ABP 25 and precursor 21 with cathepsin K.
• Probe 25 enabled sensitive detection and selective visualization of cathepsin K in complex proteomes.
• Live cell imaging confirmed the probe's applicability in a pathophysiological context.

Conclusions:

• Novel acrylamide-based Michael acceptor probes were developed for cathepsin K.
• ABP 25 is a potent and selective inhibitor and imaging agent for cathepsin K.
• These probes show promise for diagnostic and research applications in bone-related diseases.