|Title||The branched-chain aminotransferase proteins: novel redox chaperones for protein disulfide isomerase: implications in Alzheimer’s disease|
|Authors||Conway, M.E., El Hindy, M., Hezwani, M., Hull, J., Corry, D., Mansbridge, A., Hassler, M., Patel, V., Kehoe, P.G., Love, S., Harris, M., Forshaw, T., Lee, C.S., El Amraoui, F. and Wilson, A.|
Abstract Aims: The human branched-chain aminotransferase proteins (hBCATm and hBCATc) are regulated through oxidation and S-nitrosation. However, it remains unknown if they share common redox characteristics to enzymes such as protein disulphide isomerase (PDI) in terms of regulating cellular repair and protein misfolding. Results: Here, like PDI, the hBCAT proteins showed dithiol-disulphide isomerase activity mediated through an S-glutathionylated mechanism. Site-directed mutagenesis of the active thiols of the CXXC motif, demonstrate that they are fundamental to optimal protein folding. Far Western analysis indicated that both hBCAT proteins can associate with PDI. Co-immunoprecipitation studies demonstrated that hBCATm directly binds to PDI in IMR-32 cells and the human brain. Electron and confocal microscopy validated the expression of PDI in mitochondria (using Mia40 as a mitochondrial control), where both PDI and Mia40 were found to be co-localised with hBCATm. Under conditions of oxidative stress, this interaction is decreased suggesting that the proposed chaperone role for hBCATm may be perturbed. Moreover, immunohistochemistry studies show that PDI and hBCAT are expressed in the same neuronal and endothelial cells of the vasculature of the human brain, supporting a physiological role for this binding. Innovation: This study identifies a novel redox role for hBCAT and confirms that hBCATm differentially binds to PDI under cellular stress. Conclusion: These studies indicate that hBCAT may play a role in the stress response of the cell as a novel redox chaperone, which if compromised may result in protein mis-folding, creating aggregates a key feature in neurodegenerative conditions such as Alzheimer's disease.
|Journal||Antioxidants and Redox Signaling|
|Journal citation||20 (16), pp. 2497-2513|
|Publisher||Mary Ann Liebert|
|Digital Object Identifier (DOI)||doi:10.1089/ars.2012.4869|