Intrabodies prevent protein misfolding
An increasing number of human disorders, such as Alzheimer's and Parkinson's disease, result from the aggregation of misfolded proteins. Similarly, AAT deficiency that is caused by mutations in the AAT gene, leads to the accumulation of AAT polymers within the endoplasmic reticulum of hepatocytes. Mutant AAT accumulates in utero and causes cholestatic jaundice or juvenile cirrhosis. In adults it leads to liver cirrhosis and occasionally hepatocellular carcinoma. Importantly, AAT deficiency is the most important genetic factor in the development of chronic obstructive pulmonary disease. Currently, the expensive AAT replacement therapy is the only option for treating AAT deficiency or related emphysema. The primary objective of the EU-funded SERPINOPATHIES (Determination of the structure of the pathological neuroserpin polymer and development of an intrabody strategy to prevent disease-associated inclusions in cell and animal models of disease) project was to develop therapeutic strategies to prevent aggregation of misfolded proteins. In this context, the consortium used antibodies directed against specific protein polymers. SERPINOPATHIES researchers utilised an antibody that bound with high affinity to AAT in its monomeric form. They successfully blocked its polymerisation in vitro as well as in a cell model of the disease. Moreover, by mutating AAT protein they mapped the epitope that the antibody recognised and delineated the mechanism of polymerisation. Using the worm Caenorhabditis elegans as a model organism, they determined the efficacy of the drug fluphenazine at reducing protein toxicity and reversing the phenotypic effects of AAT accumulation. Furthermore, scientists engineered antibodies (intrabodies) capable of altering the fate of their target molecule inside cells. These were tested in transgenic C. elegans-expressing fluorescent AAT to study protein aggregate accumulation or clearance of polymers. Understanding how intrabodies affect survival and longevity in this model is paramount for translating its implementation in the clinic. Taken together, the findings of the SERPINOPATHIES study open up new therapeutic avenues for diseases associated with impaired protein folding.
Keywords
Alpha1-antitrypsin deficiency, hepatocyte, protein folding, intrabodies
