Investigating in vivo neuronal endolysosomal dynamics in health and aging using C. elegans

Converging evidence suggests that dysfunction of the lysosomal system, responsible for degrading cellular waste, is a critical factor underlying neurodegenerative disease and neuronal aging. However, how this age- related impairment manifests in neurons is not well-understood. This proposal will leverage the power of in vivo subcellular imaging of neurons in the nematode Caenorhabditis elegans to investigate the dynamic behavior of neuronal endolysosomal organelles and their aging-related decline. In Aim 1, the applicant Zoe Cook will train with mentor Dr. Kang Shen to characterize in vivo neuronal endolysosomal dynamics across C. elegans aging, using the highly branched PVD sensory neuron as a model. Ms. Cook will first methodically characterize the flow of endolysosomal and autophagic degradative trafficking in a healthy neuron using multiple compartment marker proteins, a pH sensor, and an in vivo protein degradation assay. She will then utilize these tools to define aging-related dysfunction in aged worms and mutants with altered lifespans. In Aim 2, Ms. Cook will investigate the mechanism and function of endolysosomal dynamics in neurons, specifically tubulation, or the extension of elongated membrane tubules. In her preliminary work, the applicant has identified the transmembrane lysosomal protein PIPP-4P, homologous to human TMEM55B, as a negative regulator of age-dependent endolysosomal tubulation in neurons. While TMEM55B is a known mediator of lysosomal transport and stress response, this function has not been previously reported; furthermore, TMEM55B has not been investigated in neurons. Ms. Cook will leverage approaches developed in Aim 1 to determine the mechanism by which PIPP-4P regulates endolysosomal tubulation and then manipulate tubule dynamics in vivo to establish their functional relevance in neurons. The training plan is tailored to enable candidate Zoe Cook to develop subject area expertise in endolysosomal biology in the context of neurodegenerative disease, as well as practical skills for data analysis, scientific presentation, and team leadership. The collaborative and innovative Neurosciences Interdepartmental Program at Stanford University will be an outstanding environment for Ms. Cook to build a strong background in neuroscience research and learn from world-renowned scientists to reach her research and training goals. Mentor Dr. Kang Shen is a leading expert in neuronal cell biology. Dr. Shen's expertise in C. elegans neuroscience will be complemented by consultants Dr. Monther Abu-Remaileh, Dr. Marius Wernig, and Dr. Tom Clandinin, all experts in diverse approaches to investigating lysosomal biology in the context of neurodegenerative disease. The proposed research will generate insights into how the endolysosomal system is dynamically regulated in neurons and where aging-related dysfunction develops, potentially informing future therapeutic approaches. Furthermore, the strong mentoring team, institutional environment, and training plan will fully prepare Zoe Cook for a postdoctoral position, the next step in her journey towards becoming an independent investigator. Project Number: 1F31AG094118-01 | Fiscal Year: 2025 | NIH Institute/Center: National Institute on Aging (NIA) | Principal Investigator: Zoe Cook | Institution: STANFORD UNIVERSITY, STANFORD, CA | Award Amount: $42,507 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F03A-E (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11160273