Stress to cells can directly influence the expression, functional role, and the subcellular distribution of molecules within cells leading to cell death and/or dysfunction. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is one of these molecules modified by cell stressors and plays a critical role in cellular stress response. Posttranslational modifications of GAPDH induced by cell stressors allow it to function as a "sensor" and/or "relay" molecule that conveys stress signals into the nucleus by forming a complex with another protein called seven in absentia homolog 1 (Siah). In the nucleus this GAPDH-Siah complex causes various changes within the cell that have been associated with cell death and dysfunction. Activation of the GAPDH-Siah cascade demonstrated in Parkinson's disease (PD), and the nuclear colocalization of GAPDH and Huntingtin seen in Huntington's disease (HD), suggest that the GAPDH-Siah cascade may drive these neurodegenerative diseases. However, strong support for this idea is lacking. Our recent finds suggests that a third protein called apoptosis signal regulating kinase 1 (ASK1) might also be capable of triggering the GAPDH-Siah stress signaling cascade. Through the proposed training grant we will provide evidence to demonstrate that ASK1 activates the GAPDH-Siah stress signaling cascade in Huntington's disease by;1) determining how ASK1 and GAPDH affect ASK1-Siah binding, 2) clarifying how ASK1 triggers GAPDH-Siah stress signaling and 3) directly examining the role of ASK1, GAPDH, and Siah in HD pathology.
Characterization of this novel stress-signaling cascade will help us understand the molecular mechanism underpining the progression of neurodegenerative diseases, such as HD. Characterization of this cascade in the context of neurodegeneration may help us identify potential therapeutic targets for the treatment of these diseases.