Funded Studies
Objective/Rationale:
Glucose regulating protein 78 (GRP78/BiP), also known as BiP or HSPA5, is a member of the HSP70 family of chaperones. Along with its role in protein folding, GRP78/BiP is also known to be an important component in modulating the unfolded protein response (UPR). Aging leads to a significant decline of the GRP78/BiP expression in the brains of old vs. young pre-clinical models, and is thought to contribute to age-related impairments in cellular function.
Project Description:
We will over-express human GRP78/BiP via AAV mediated transfer. We will focus on one well established pre-clinical model of Parkinson-like degeneration: AAV mediated over-expression of human alpha-synuclein. We will follow the progression of neurodegeneration by looking at the number of TH-positive neurons, the levels of striatal dopamine. By relieving the UPR or blocking some of the early signals leading to cell death, we hope to preserve nigral DA cells and maintain their function. Also we will test whether GRP78/BiP expression decline during aging is a predisposing factor for PD progression. We will inject viruses expressing small interfering RNA (siRNA) specific to GRP78/BiP into the substantia nigra over-expressing clinical alpha-synuclein to test a dependence of nigral vulnerability on GRP78/BiP production level.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
Successful completion of this study will determine whether components of UPR signaling present valuable therapeutic targets for alpha-synuclein induced neurotoxicity. Our approach is not limited in application to gene therapy only. It would also hold great promise for subsequent target-based drug discovery for PD.
Anticipated Outcome:
Since we will study the activation of UPR signaling, apoptosis and pathogenic markers in BiP-treated and BiP–untreated PD pre-clinical models, we expect to reveal new potential therapeutic targets.
Progress Report
Using AAV mediated gene transfer we overexpressed ER chaperone GRP78/BiP , to test the hypothesis that this ER chaperone modulates the UPR, blocks apoptosis, and promotes the survival of nigral dopamine (DA) neurons in a pre-clinical model of Parkinson's disease induced by elevated level of human α-syn. We determined that α-syn activates ER stress mediators associated with PKR–like Endoplasmic Reticulum Kinase and Activating Transcription Factor-6 signaling pathways as well as pro-aoptotic CCAAT/-enhancer-binding protein homologous protein in nigral DA neurons. At the same time, overexpression of GRP78/BiP diminished α-syn neurotoxicity by down regulating ER stress mediators and the level of apoptosis, promoted survival of nigral tyrosine hydroxylase positive cells and resulted in higher levels of striatal DA, while eliminating amphetamine induced behavioral asymmetry. We also detected a complex between GRP78/BiP and α-syn that may contribute to prevention of the neurotoxicity caused by α-syn. Our data suggest that the molecular chaperone GRP78/BiP plays a neuroprotective role in α-syn induced Parkinson-like neurodegeneration.
Final Outcome
GRP78/BiP is a key protein in ER stress signaling, whose expression is modulated in degenerative cells depending on their stage of ER stress and the unfolded protein response (UPR). Expression of GRP78 has been demonstrated to decrease with age, raising the question of whether the lack of GRP78 could be a predisposing factor for most degenerative disorders associated with age. The conducted studies highlight the importance of controlling UPR signaling as a means for curtailing the progression of neurodegenerative disorders associated with ER stress. The studies also validated GRP78 as a prospective new and key therapeutic target for future treatment of a potentially wide spectrum of neurodegenerative diseases.
Presentations & Publications
- Gorbatyuk MS, Shabashvili A, Chen W, Meyers C, Sullivan LF, Salganik M, Lin JH, Lewin AS, Muzyczka N, Gorbatyuk OS. Glucose regulated protein 78 diminishes α-synuclein neurotoxicity in a rat model of Parkinson disease. Mol Therap., 2012 Jul; 20(7): 1327-37
- Gorbatyuk MS and Gorbatyuk OS. The Molecular Chaperone GRP78/BiP as a Therapeutic Target for Neurodegenerative Disorder. J Genet Syndr Gene Ther (Accepted March 7, 2013)
- O.S. GORBATYUK, M. SALGANIK, V. G. SERGEYEV, C. MAYERS, C. ZHONG, S. ZOLOTUKHIN, M. GORBATYUK, J. H. LIN. Is age-related decline of glucose regulated protein 78 (GRP78) a predisposing factor for Parkinson disease? Society for neuroscience Meeting 2013, San Diego. Abstract submitted for slide presentation.
Manuscripts in Preparation
- Maxim Salganik, Valeriy G. Sergeyev, Craig Mayers, Can Zhong, Marina Gorbatyuk, Jonathan Lin, Sergey Zolotukhin and Oleg S. Gorbatyuk. Age-related decline of GRP78/BiP determines neurodegeneration in a rat model of Parkinson disease.
- Maxim Salganik, Craig Mayers, Can Zhong and Oleg S. Gorbatyuk. Long-term over-expression of GRP78/BiP protein protects ageing nigral DA neurons rat model of Parkinosn-like neurodegeneration..