Improved quenched fluorescent probe for imaging of cysteine cathepsin activity

Item does not contain fulltextThe cysteine cathepsins are a family of proteases that play important roles in both normal cellular physiology and many human diseases. In cancer, the activity of many of the cysteine cathepsins is upregulated and can be exploited for tumor imaging. Here we present the design and synthesis of a new class of quenched fluorescent activity-based probes (qABPs) containing a phenoxymethyl ketone (PMK) electrophile. These reagents show enhanced in vivo properties and broad reactivity resulting in dramatically improved labeling and tumor imaging properties compared to those of previously reported ABPs

Design of a highly selective quenched activity-based probe and its application in dual color imaging studies of cathepsin S activity localization

The cysteine cathepsins are a group of 11 proteases whose function was originally believed to be the degradation of endocytosed material with a high degree of redundancy. However, it has become clear that these enzymes are also important regulators of both health and disease. Thus, selective tools that can discriminate between members of this highly related class of enzymes will be critical to further delineate the unique biological functions of individual cathepsins. Here we present the design and synthesis of a near-infrared quenched activity-based probe (qABP) that selectively targets cathepsin S which is highly expressed in immune cells. Importantly, this high degree of selectivity is retained both in vitro and in vivo. In combination with a new green-fluorescent pan-reactive cysteine cathepsin qABP we performed dual color labeling studies in bone marrow-derived immune cells and identified vesicles containing exclusively cathepsin S activity. This observation demonstrates the value of our complementary cathepsin probes and provides evidence for the existence of specific localization of cathepsin S activity in dendritic cells