Vertebrate retinas have two types of photoreceptor cells - rods and cones. Rods are exquisitely sensitive to light but cones are more critical for daytime vision, acuity and color discrimination. Cone cells can be adversely affected by genetic mutations and can become secondary casualties of rod degeneration. Environmental factors and aging also can affect cone survival, thereby contributing to age-related macular degeneration. However, little is known about the fine structure of cones due to the paucity of cone cells and lack of proper methods to investigate them has impeded studies of the fine structure. Our long-term objective of this research is to elucidate the detailed structural features of cone photoreceptors critical for their function and survival. Cone phototransduction is initiated by activation of cone pigments (opsins), membrane-bound proteins that are prototypic G protein-coupled receptors (GPCRs). While rhodopsin comprises ~90% of protein in rod disc membranes, the composition and organization of opsins in cone cells have yet to be determined. Such information would be broadly applicable to other signal transduction cascades because GPCRs represent the largest known class of drug, hormone and neuropeptide receptors. Here we propose three thematically linked specific aims related to the structural biology of cone cells: (1) Determine the detailed structure of cone cells in transgenic mice lacking transcriptional factor NRL, a rodent model of enhanced S-cone syndrome in humans. These mice exclusively produce cone-like photoreceptors that will be examined by cryo-electron tomography. The abundance of cone-like cells in this transgenic species will allow creation of protocols required for efficient extraction and imaging studies. (2) Use cryo-electron tomography to elucidate the fine structure of cones in the Nile rat, an animal that has ~33% cone cells compared to ~1% in most other rat species. This study will allow us to discern the native cone structure as compared with rods in the same species. Moreover, the experimental findings in this diurnal rodent should be more generalizable to human photoreceptor ultrastructure and function. (3) Determine the organization of cone pigments in individual disc membranes from both NRL transgenic mice and Nile rats. This will allow us to observe directly if and how the organization of visual pigments differs between rod and cone cells. Information about their organization would improve understanding of human disease states in which rod and cone photoreceptor function is impaired.

Public Health Relevance

Vertebrate retinas have two types of photoreceptor cells - rods and cones. Cones are critical for our daytime vision, acuity and color discrimination and their health is affected by genetic mutations, environmental factors and aging. Yet our knowledge of cones is scanty because they comprise only about 5% of photoreceptor cells in the human retina. Thus, the long-term objective of our research is to elucidate the detailed structural features of cone photoreceptors central to their function and survival.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY019478-04
Application #
8266463
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Neuhold, Lisa
Project Start
2009-05-01
Project End
2014-04-30
Budget Start
2012-05-01
Budget End
2013-04-30
Support Year
4
Fiscal Year
2012
Total Cost
$373,032
Indirect Cost
$135,432
Name
Case Western Reserve University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Orban, Tivadar; Jastrzebska, Beata; Palczewski, Krzysztof (2014) Structural approaches to understanding retinal proteins needed for vision. Curr Opin Cell Biol 27:32-43
Chen, Yuanyuan; Jastrzebska, Beata; Cao, Pengxiu et al. (2014) Inherent instability of the retinitis pigmentosa P23H mutant opsin. J Biol Chem 289:9288-303
Jastrzebska, Beata; Ringler, Philippe; Palczewski, Krzysztof et al. (2013) The rhodopsin-transducin complex houses two distinct rhodopsin molecules. J Struct Biol 182:164-72
Mustafi, Debarshi; Kevany, Brian M; Genoud, Christel et al. (2013) Photoreceptor phagocytosis is mediated by phosphoinositide signaling. FASEB J 27:4585-95
Mustafi, Debarshi; Kevany, Brian M; Bai, Xiaodong et al. (2013) Evolutionarily conserved long intergenic non-coding RNAs in the eye. Hum Mol Genet 22:2992-3002
Palczewski, Krzysztof; Orban, Tivadar (2013) From atomic structures to neuronal functions of g protein-coupled receptors. Annu Rev Neurosci 36:139-64
Vahedi-Faridi, Ardeschir; Jastrzebska, Beata; Palczewski, Krzysztof et al. (2013) 3D imaging and quantitative analysis of small solubilized membrane proteins and their complexes by transmission electron microscopy. Microscopy (Oxf) 62:95-107
Jastrzebska, Beata; Orban, Tivadar; Golczak, Marcin et al. (2013) Asymmetry of the rhodopsin dimer in complex with transducin. FASEB J 27:1572-84
Salom, David; Wang, Benlian; Dong, Zhiqian et al. (2012) Post-translational modifications of the serotonin type 4 receptor heterologously expressed in mouse rod cells. Biochemistry 51:214-24
Mustafi, Debarshi; Kevany, Brian M; Genoud, Christel et al. (2011) Defective photoreceptor phagocytosis in a mouse model of enhanced S-cone syndrome causes progressive retinal degeneration. FASEB J 25:3157-76

Showing the most recent 10 out of 18 publications