A fascinating question in Vision Research is how the lens, a tissue made of concentric layers of living fiber cells, maintains both transparency and homeostasis in the absence of blood vessels and for the life of the animal. In the current model, a primitive """"""""circulatory system"""""""" comprised of channels and transporters is thought to move water, ions, and nutrients, and thereby maintain the metabolic integrity of the lens interior. A high concentration (450 mg/ml) of soluble proteins of the crystallin family forms a gel-like structure responsible for the refractive properties yielding transparency. Disruption of either the system of channels or the assemblies of crystallins results in a loss of transparency and the formation of cataracts. This application proposes to determine the 3D-structure and protein composition of the macromolecular assemblies underpinning lens transparency and cataract formation in vertebrate lenses. To accomplish this goal, experiments are proposed to determine the 3D-structure of these assemblies, using the newly perfected techniques of Conical Electron Tomography and Density Segmentation. This approach will allow us for the first time to determine the changes in the 3D- structure of assemblies at high resolution (~3 nm), in their cellular environments and without the need to impose symmetry or to average over many molecules. The three aims comprising the application will focus specifically on: a) membrane-bound assemblies comprised of AQP0, Cx46 and Cx50, b) """"""""beaded"""""""" filaments of the fiber cytoskeleton, composed of filensin and phakinin, and c) assemblies comprised of 1-crystallin. Changes in the 3D-structure of these assemblies that are induced by protein phosphorylation, a single amino acid replacement in the central domain of the 1-crystallin (1A-Y118D) that induces a nuclear cataract in rodents and humans will be studied using Conical Tomography and Density Segmentation. We expect that a better understanding of the changes in the 3D-structure and protein composition of these assemblies will lead to strategies that might slow down or prevent the onset of cataract.

Public Health Relevance

Cataracts are the principal cause of blindness worldwide. Once the disease develops, it can only be treated by surgery. In the last year alone, almost three million Americans required surgical procedures to remove lenses and restore vision, with expenses in the billions. The identification of agents that might slow down or completely prevent the appearance of the disease requires a detailed understanding of the 3D-structure and protein composition of the assemblies responsible for lens transparency.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY004110-26A1
Application #
7714900
Study Section
Anterior Eye Disease Study Section (AED)
Program Officer
Araj, Houmam H
Project Start
1982-08-01
Project End
2012-06-30
Budget Start
2009-07-01
Budget End
2010-06-30
Support Year
26
Fiscal Year
2009
Total Cost
$371,500
Indirect Cost
Name
University of California Los Angeles
Department
Neurosciences
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Zampighi, Guido A; Serrano, Raul; Vergara, Julio L (2014) A novel synaptic vesicle fusion path in the rat cerebral cortex: the ""saddle"" point hypothesis. PLoS One 9:e100710
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Zampighi, Guido A; Fain, Nick; Zampighi, Lorenzo M et al. (2008) Conical electron tomography of a chemical synapse: polyhedral cages dock vesicles to the active zone. J Neurosci 28:4151-60
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Zampighi, G A; Zampighi, L M; Fain, N et al. (2006) Conical electron tomography of a chemical synapse: vesicles docked to the active zone are hemi-fused. Biophys J 91:2910-8
Lin, Dingbo; Barnett, Micheal; Lobell, Samuel et al. (2006) PKCgamma knockout mouse lenses are more susceptible to oxidative stress damage. J Exp Biol 209:4371-8
Hegde, Balachandra G; Isas, J Mario; Zampighi, Guido et al. (2006) A novel calcium-independent peripheral membrane-bound form of annexin B12. Biochemistry 45:934-42
Zampighi, Guido A (2003) Distribution of connexin50 channels and hemichannels in lens fibers: a structural approach. Cell Commun Adhes 10:265-70

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