Identifying Regulators of Lysosome Reformation: Inhibitor Screen in Mammalian Cell Culture

Abstract

Lysosomes are membrane-bound organelles that have diverse functions in eukaryotic cells. Malfunctions in lysosomes result in a range of diseases known as Lysosomal Storage Disorders. After fusing with late endosomes to form hybrid organelles, lysosomes bud off and are reformed in a poorly characterized process known as lysosome formation or reformation. Only one mammalian regulator of lysosome formation has been identified, the non-selective cation channel TRPML1. In the highly similar process of Autophagic Lysosome Reformation (ALR), three known regulators have also been identified, the vesicle-coating protein clathrin and two phosphatidylinositol kinases that catalyze the formation of the membrane phospholipid PI(4,5)P₂. Here, we use an inhibitor screen coupled with a live imaging assay to identify the actin microfilament as a novel regulator of lysosome formation.