Metabolic Lysosomal Enzyme Probes

Lysosomes are acidic cytoplasmic organelles that are present in all nucleated mammalian cells. Lysosomes have been found to be involved in a variety of cellular processes including repair of the plasma membrane, defense against pathogens, cholesterol homeostasis, bone remodeling, metabolism, apoptosis and cell signaling. Defects in lysosomal enzyme activity have been associated with a variety of diseases including Parkinson's, Tay‐Sachs, Sandhoff, Krabbe and Gaucher's syndromes. New lysosomal staining compounds that are useful for labeling lysosomes in a live‐cell format and are capable of monitoring lysosomal metabolic activity have been developed. These new targeted substrates are based upon fluorescent probes that have a low pKa value for optimum fluorescence at the lower physiological pH values found in the lysosomes as well as targeting groups to direct their accumulation to the lysosomes using a live‐cell staining format. Application to the staining of cells derived from patients with Krabbe's, Gaucher's I and II, Tay‐Sach's and Sandhoff Diseases as well as healthy human and murine fibroblast control cells are presented. In addition the ability to monitor the effect of secondary therapeutic agents on staining is presented. This work was supported by NIH Grant 5R43MH079542‐02.