Although glia, the non-neuronal cells of the brain, are increasingly implicated in aging and neurodegenerative disease, we know very little about how these cells interact with neurons during aging. Neurodegenerative diseases, like Alzheimer's disease, are characterized by aggregated misfolded proteins, which can cause cell death and dysfunction. Cells have developed systems to detect and fix these problems in a cellular compartment-specific manner; however, these responses to protein misfolding start to fail as organisms age. We have previously shown that neurons send out signals to alert other cells when they experience protein toxicity and stress, which could be a clue towards how the body could naturally fix protein misfolding in neurodegenerative disease. However, no one has yet investigated how glia respond to protein stress in the cytosolic compartment of the cell. Our laboratory previously showed that neuronal over-expression of the main regulator of the cytosolic unfolded protein response, heat shock factor 1 (HSF-1), is able to signal to distal cells to increase healthy protein folding effectors and help organisms live longer. Here, we propose that glial cells can also signal the heat shock response to coordinate a pan-organismal response and promote longevity (Aim 1). Our approach in this aim takes advantage of the genetic tractability, short lifespan, and simple imaging of the model organism, C. elegans, to study non-cell autonomous signaling between tissues in aging. To further address the role of glia in rescuing neurons from protein toxicity, we will examine microglia in the mammalian brain. Here, we ask whether healthy microglia can rescue neurons stressed with tau protein misfolding, which is a common feature of Alzheimer's disease and other dementias, and whether aged microglia might be defective in their aid to neurons. We will assess how microglia surveil the internal protein homeostasis of neurons (Aim 2). To do this, we will take advantage of transcriptome analysis, inducible mouse disease models, and rapidly improving cell culture methods. Data generated through this proposal will shed new light on how the brain deals with protein stress and will identify novel signaling mechanisms of glial cells that will improve our understanding of neurodegenerative disease pathology.
Glial-neuronal interactions underlie a broad range of aging-associated disease phenotypes in the nervous system and beyond. Activation of the heat shock response (HSR) has been shown to extend lifespan and promote healthy aging, but until this proposal, glial signaling of the HSR has never been examined. This proposal studies the mechanism by which glial stress response induction can extend lifespan, and further proposes extending this work using microglia/neuronal interaction in tauopathies to interrogate the ways in which microglia signal aging-related stress responses to protect neurons.
