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Title: Factors that affect the folding, aggregation and degradation of rod opsin
Author: Athanasiou, D.
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2013
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Mutations in rhodopsin, the light sensitive protein of rod cells that mediates night vision, are the most common cause of autosomal dominant retinitis pigmentosa (ADRP). Many rod opsin mutations such as P23H lead to misfolding of rod opsin and to its accumulation within the cell, with detrimental effects on photoreceptor function and viability. Therefore, it is important to address the role of molecular chaperones in rod opsin biogenesis and subsequently in the disease. This study shows that BiP, the hsp70 protein of the ER, is important for rod opsin biogenesis. Depletion of BiP with the subtilase cytotoxin (SubAB) or inhibition of BiP function results in aggregation of wild-type (WT) rod opsin in the ER. By contrast, BiP overxpression improves P23H rod opsin ER mobility suggesting that it can be used as a tool to reduce rod opsin aggregation and highlighting a role of BiP in maintaining rod opsin solubility in the ER. The reductase protein ERdj5 that acts as a co-chaperone for BiP can promote P23H rod opsin degradation and its overexpression can improve P23H mobility in the ER. Moreover, loss of the reductase activity of ERdj5 can impair WT rod opsin traffic to the plasma membrane and decrease its mobility in the ER. Misfolded P23H rod opsin is characterised by the formation of an incorrect disulphide bond between C185-C187 (as opposed to the correct C110-C187). Therefore, the role of the reductase activity of ERdj5 in dealing with misfolded rod opsin was further investigated by studying WT rod opsin or P23H mutation in combination with amino acid substitutions that prevent the formation of incorrect disulphide bonds. These mutants confirmed a role of the disulphide bond formation/reduction in rod opsin biogenesis and disease, but illustrated that the situation is complex. Finally, improvement of P23H traffic and P23H cell viability was achieved by treatment with compounds that activate AMP kinase, the master regulator of cellular energy homeostasis. The effect of these compounds and chaperones can now be tested in animal models of ADRP.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available