Accumulation of toxic proteins (i.e. A?42 & tau) and dysfunctional mitochondria are associated with synaptic and neuronal loss in multiple neurodegenerative disorders, including Alzheimer?s disease (AD). Such clearance defects are thought to arise in large part from deficits in the autophagy-lysosome system. While mounting experimental evidence supports the notion that AD is a tauopathy at least in part driven A?, there is still a considerable knowledge gap in the way A? and tau pathogenesis are mechanistically connected. Our recently published and preliminary studies indicate that the Slingshot homolog-1 (SSH1) pathway constitutes a critical link between A? and tau pathogenesis. SSH1 is a protein phosphatase, classically known for its cofilin dephosphorylating activity. SSH1 is activated by oxidative stress (i.e. H2O2, A?, etc.) and/or intracellular Ca2+ elevation, which results in activation / dephosphorylation of cofilin. Activated cofilin can then sever F-actin (at the synapse) and/or translocate to mitochondria to promote mitochondria-mediated apoptosis. Likewise, we have found that activation of SSH1 and cofilin are required for A?42-induced mitochondrial dysfunction, synaptic loss, as wells as deficits in LTP and/or learning/memory in cellular and mouse models of A pathogenesis (APP/PS1). In support of these experimental findings, activated cofilin and SSH1/cofilin complexes are increased in APP/PS1 mouse brains as wells as in mitochondria of AD brains. In preliminary studies, we found that in addition to cofilin, SSH1 contains a modular and independent activity on the autophagy cargo receptor p62, which functions to regulate autophagy and tau clearance. By utilizing molecular, biochemical, cell biological, viral, and histochemical tools, we propose to (1) dissect the modular activity of SSH1 in p62-mediated autophagy and mitophagy; and (2) determine the role of SSH1 in p62-mediated autophagy and tauopathy in vivo.
Accumulation of toxic proteins (i.e. A?42 & tau) and dysfunctional mitochondria are associated with synaptic and neuronal loss in multiple neurodegenerative disorders, including Alzheimer?s disease (AD). This application utilizes cellular and animal models combined with molecular gene expression tools to understand the mechanistic basis of toxic tau protein and dysfunctional mitochondria accumulation in AD pathogenesis. The proposed studies are expected to shed novel insights to how a defined and separable function of SSH1 protein mediates these processes.
