Research Projects

Lysosomes, acidic membrane-bound organelles found in all mammalian cells, play a crucial role in protein degradation and membrane fusion. However, our understanding of the molecular mechanisms driving lysosome secretion is limited. This grant application aims to use osteoclasts (OCs) as a model system to better understand the molecular machinery regulating lysosome exocytosis/secretion to maintain bone homeostasis. Bone diseases can be caused by hyperactivity of OCs, which are responsible for bone resorption. Only a few Rabs have been functionally described in OCs, despite their extensive expression and roles in other cell systems. Aim 1 involves isolating lysosomes from OCs and using mass spectrometry to identify Rab proteins associated with lysosomes. Gene silencing approaches (siRNA and/or CRISPR-Cas9) will be used to investigate the functional role of lysosome-associated Rab proteins in regulating lysosome trafficking and secretion. Mutations in various lysosomal proteins, such as PLEKHM1, cause genetic abnormalities that impair OC function. PLEKHM1-deficient OCs exhibit decreased resorptive activity and increased intracellular lysosome accumulation, indicating that PLEKHM1 is a crucial regulator of intracellular lysosome trafficking and secretion in OCs. Aim 2 of the grant proposal focuses on the role of the Arl8b-PLEKHM1-Rab7 ternary complex in lysosome trafficking. The findings will significantly expand our understanding of lysosome exocytosis/secretion and may provide strategies for the prevention and treatment of various human diseases, including lysosome storage diseases and bone loss.