Date of Award
Doctor of Philosophy (PhD)
Axons are unique compartments of neurons that extend tremendous distances throughout the body. Neurodegenerative or traumatic damage to axons destroys neuronal function and thus necessitates axonal repair. Mammalian peripheral neurons can regrow their axons following injury, providing a robust system to study the molecular mechanisms of axon regeneration. Injury induces a large transcriptional program that drives regeneration. While many regeneration-associated genes are known, the mechanisms by which injury activates them are less well understood. Identification of new injury signals has been limited by in vivo approaches. To address this challenge, I developed and performed a loss-of-function pharmacological screen in cultured adult mouse sensory neurons for proteins required to activate this program. Well-characterized inhibitors were present as injury signaling was induced, but were removed before axon outgrowth to identify molecules that block induction of the program. The top hits were inhibitors to heat shock protein 90 (HSP90), a chaperone with no known role in axon injury. HSP90 inhibition blocks injury-induced activation of several regeneration-associated genes and proteins. These phenotypes mimic loss of the pro-regenerative MAP3K, dual leucine zipper kinase (DLK), a critical neuronal stress sensor that drives axon degeneration, axon regeneration, and cell death. HSP90 is an atypical chaperone that promotes the stability of signaling molecules. In neurons, HSP90 and DLK demonstrate the two hallmarks of a HSP90-client relationship: 1) HSP90 binds DLK and 2) HSP90 inhibition leads to rapid degradation of existing DLK protein. Thus, this dissertation demonstrates that HSP90 chaperones DLK and is required for DLK functions, including pro-regenerative axon injury signaling. Further, this work introduces a high-content, unbiased method to identify novel components of axon injury signaling.
Chair and Committee
Valeria Cavalli, Jeffrey Milbrandt, Zachary Pincus, James Skeath,
Karney-Grobe, Scott, "A high-content screen identifies HSP90 as a component of axon injury signaling" (2018). Arts & Sciences Electronic Theses and Dissertations. 1630.