Molecular Mechanism of αAN101D-Transgene-Induced Age-Related Cataract

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The proposal has the overall goal to determine the molecular mechanisms of an age-related cortical cataract development. Cataracts are principally a lens structural proteins' (crystallins) aggregation and subsequent precipitation disease that are inducible by genetic mutations, and occurs due to aging. During cataract development, the increased sizes of aggregated and cross-linked crystallin multimers become so large that they finally become water insoluble and cause lens opacity. Several post-translational modifications (PTMs) of crystallins are known to cause age-related cataracts, and the deamidation of crystallins (the most abundant among post-translational modifications) is considered as a major cataract-causative factor. In spite of voluminous literature on in vitro studies of effects of crystallins' deamidation leading to cataract-development, no clear molecular mechanism has emerged that could implicate the deamidation-induced link of the in vitro effects to in vivo changes. Therefore, the PI's-generated unique αA-N101D mouse model, where asparagine 101 is deamidated to aspartic acid, provides an opportunity to directly link the in vitro studies to in vivo changes in phenotypic and crystallins' properties to the cortical cataract development. The model would provide information about the molecular mechanism of age-related cataract development. Based on our extensive results, we have hypothesized that the cataract in αAN101D mouse model is caused by the altered crystallin properties, cellular defects and synergistically increased deposit of αAN101D with membrane, resulting in membrane disruption and ionic imbalance. We plan to test the above hypothesis by seeking answers the following three questions using the above mouse model: (A) Aim 1: Does deamidated αAN101D causes temporal alterations in crystallin- crystallin interactions leading to aggregation among crystallins and their insolubilization in vivo? (B) Aim 2: What are the temporal sequence of lens phenotypes that cause cellular defects during the cortical cataract development? (C) Aim 3: Does temporal increase in binding of deamidated αAN101D to membrane leads to membrane disorganization and intracellular ionic imbalance? The results will be of significant therapeutic value to delay the development and progression of age-related cataracts.