A novel fluorogenic reporter substrate for 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase gamma-2 (PLCγ2): Application to high-throughput screening for activators to treat Alzheimer's disease

A high-throughput assay platform to discover small molecule activators of the phospholipase PLC-γ2 to treat Alzheimer's disease

A naturally occurring missense variant of the phospholipase C isozyme, PLC-γ2, harboring a single substitution (P522R) protects against several neurodegenerative diseases, including Alzheimer's disease. The phospholipase activity of PLC-γ2 (P522R) is slightly elevated relative to its WT counterpart, and the general consensus is that this increased activity in microglia confers protection against neurodegeneration. In order to phenocopy this protection, we have developed a high-throughput assay to identify small molecule activators of PLC-γ2. The assay takes advantage of the fluorescent reporter, XY-69, embedded in lipid vesicles to readout the allosteric activation of PLC-γ2. The assay is highly reproducible and capable of identifying compounds with a large range of efficacies. A series of secondary assays have been established to define the selectivity of compounds for PLC-γ2, establish relevant activation of PLC-γ2 by compounds in a microglia cell line, and measure affinities between PLC-γ2 and hit compounds. The established workflow was prototyped using approximately 6000 compounds to produce several promising hits, but more importantly, enables screens of much larger chemical libraries to identify selective activators of PLC-γ2 to be used as chemical probes and drug leads.

A novel micellular fluorogenic substrate for quantitating the activity of 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase gamma (PLCγ) enzymes

The activities of the phospholipase C gamma (PLCγ) 1 and 2 enzymes are essential for numerous cellular processes. Unsurprisingly, dysregulation of PLCγ1 or PLCγ2 activity is associated with multiple maladies including immune disorders, cancers, and neurodegenerative diseases. Therefore, the modulation of either of these two enzymes has been suggested as a therapeutic strategy to combat these diseases. To aid in the discovery of PLCγ family enzyme modulators that could be developed into therapeutic agents, we have synthesized a high-throughput screening-amenable micellular fluorogenic substrate called C16CF3-coumarin. Herein, the ability of PLCγ1 and PLCγ2 to enzymatically process C16CF3-coumarin was confirmed, the micellular assay conditions were optimized, and the kinetics of the reaction were determined. A proof-of-principle pilot screen of the Library of Pharmacologically Active Compounds 1280 (LOPAC1280) was performed. This new substrate allows for an additional screening methodology to identify modulators of the PLCγ family of enzymes.