TRPML1 Protein Functions in Lysosome Biogenesis

University Of Arizona, Tucson AZ

Investigators

Abstract

Intellectual merit. The aim of this project is to decipher mechanisms of lysosome biogenesis. Lysosomes are the main membrane-bound, degradative organelles of eukaryotic cells. In addition to degrading molecules taken up from the extracellular medium by endocytosis, lysosomes regulate multiple essential cellular processes, including normal turnover of components of cellular organelles, degradation of cellular material in response to starvation, degradation of signaling receptors as needed to regulate developmental pathways, fusion with the plasma membrane to initiate wound healing, and participation in some cell death pathways. Given this central importance of lysosomes, it is striking that little is known about basic principles of how lysosomes are formed. Studies have shown that lysosomal biogenesis proceeds by budding of a membrane extension from the endosomal compartment followed by vesicle scission to release a newly formed lysosome. Preliminary studies for this project identified the TRPML1 protein as an initial regulator of lysosome biogenesis. The studies showed that this protein, which has also been shown to be a channel protein that is dysfunctional in lysosomal storage disorders, is required for the membrane extension and scission steps. Based on protein interactor analyses and drug inhibition studies, a model of lysosome biogenesis was proposed in which TRPML1 recruits proteins following budding that initiate actin fiber formation at the sites of lysosome biogenesis. TRPML1 channel activity then promotes actin polymerization/force generation that leads to membrane extension and eventually scission. This project tests this model and will establish the first detailed mechanistic view of lysosomal biogenesis. Broader impacts. These studies will transform current views of membrane transport by establishing the first molecular model of lysosomal biogenesis that likely will lead to new understanding of both lysosomal and other transport processes. In addition, this research program will rely heavily on direct undergraduate participation to conduct the experiments for which the PI will provide a mentorship role. This faculty member will continue training efforts, which in the past nine years have involved twenty undergraduate students, including thirteen from under-represented groups. As in the past, the majority of these students will likely continue in graduate programs, will present the results of this research at conferences, and will be co-authors on peer-reviewed publications. The research program will be used as a platform for the scientific development of the next generations of scientists and health professionals from this institution.