Harnessing Functional Plasticity of Enzymes:  A Fluorogenic Probe for Imaging 17β-HSD10 Dehydrogenase, an Enzyme Involved in Alzheimer's and Parkinson's Diseases

In this paper, we describe the development of a fluorogenic substrate for 17β-hydroxysteroiddehydrogenase type 10 (17β-HSD10), which is a multifunctional metabolic enzyme fulfilling several metabolic roles (β-oxidation of fatty acids, catabolism of isoleucine, and metabolism of steroids). In recent years, it has emerged as an important stress and pathological marker in neurons and glial cells (expression down-regulation in Parkinson's disease, up-regulation and association with β-amyloid peptide in Alzheimer's disease). Through the iterative molecular design and chemical synthesis described herein, compound 1 was developed, which possesses all required properties for a selective optical reporter substrate:  alcohol−ketone optical switching, the ability to function as a good enzyme substrate (expressed in kinetic parameters), cell permeability, and cell retention. Probe 1 provides a blue-to-green/yellow bright switch and enables non-invasive, real-time imaging of 17β-HSD10 in live human cells. The selectivity of reporter 1 was established by the quantitative correlation of metabolic activity to protein expression in human kidney cell line HEK-293T.