Abstract

Ubiquitin E3 ligases (E3s) operate at the end of a multi-enzyme cascade involving E1, E2 and E3 enzymes. E3s have become attractive therapeutic targets yet the development of potent and selective inhibitors has proven challenging. Once aspect that has hindered inhibitor development is the need to reconstitute the entire enzymatic cascade. We have developed semisynthetic protein sensors that serve as activity-based probes for a subtype of E3s (~50), which have been implicated with disease such as cancer, autoimmunity and neurodegeneration. The ABPs allow direct assessment of E3 activity, independent of E1, E2 and substrate, in a variety of sample types ranging from purified protein to clinical samples. I will discuss how these ABPs can be deployed to study E3 regulatory biology and also serve as a valuable biomarker for assessing disease predisposition. I will also discuss how these tools have been used to discover an entirely novel subtype of E3 which presents an exciting therapeutic opportunity for the treatment of a range of neurological disorders. These ABPs should also find value in facilitating the screening of E3 modulators and their selectivity profiling thus rendering this promising target class more tractable.