July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Detection, quantification, and evaluation of the homogeneity of lipid domains in intact membranes of eye lens fiber cells
Author Affiliations & Notes
  • Witold Karol Subczynski
    Biophysics, Medical College on Wisconsin, Milwaukee, Wisconsin, United States
  • Natalia Stein
    Biophysics, Medical College on Wisconsin, Milwaukee, Wisconsin, United States
  • Laxman Mainali
    Biophysics, Medical College on Wisconsin, Milwaukee, Wisconsin, United States
  • William J O'Brien
    Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
  • Footnotes
    Commercial Relationships   Witold Subczynski, None; Natalia Stein, None; Laxman Mainali, None; William O'Brien, None
  • Footnotes
    Support  NIH Grants: R01 EY015526, P41 EB001980, and P30 EY001931
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 3034. doi:
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      Witold Karol Subczynski, Natalia Stein, Laxman Mainali, William J O'Brien; Detection, quantification, and evaluation of the homogeneity of lipid domains in intact membranes of eye lens fiber cells
      . Invest. Ophthalmol. Vis. Sci. 2018;59(9):3034.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Plasma membranes of the eye lens fiber cells are loaded with cholesterol (Chol) and are dense with integral membrane proteins, which determine the organization of the lipid bilayer portion of the membranes. The goal of this research was to discriminate lipid domains existing in intact eye lens fiber cell membranes, quantify the amounts of lipids (phospholipids [PLs] and Chol) in these domains, and obtain information about the homogeneity of these domains.

Methods : Continuous wave and saturation-recovery electron paramagnetic resonance (EPR) spin-labeling methods have been developed and applied to identify and quantify lipid domains, as well as evaluate of their homogeneity. PL-analog spin labels were used to obtain information about the organization and distribution of PLs and Chol-analog spin labels to obtain similar information about Chol.

Results : Four types of lipid domains were identified in the intact membranes of the eye lens fiber cells. They include bulk lipids, boundary lipids, trapped lipids, and the cholesterol bilayer domain (CBD). The bulk lipid domain contains lipids nearly unaffected by the presence of membrane proteins. The two domains unique to intact membranes—namely, the boundary lipids and the trapped lipids—are formed due to the presence of membrane proteins. The CBD is a highly fluid pure Chol bilayer surrounded by the bulk lipid domain formed by PLs saturated with Chol. The amount of PLs in boundary and trapped domains and the amount of Chol in trapped domains were greater in nuclear than in cortical membranes. These differences increase with the age of the donor. CBDs were detected in intact fiber cell membranes, but only when they were also detected in the lens lipid membranes prepared from the total lipid extracts from the appropriate fiber cell membranes. It was also shown that inhomogeneity of lipid domains is greater in nuclear than in cortical membranes and increases with the age of the donor.

Conclusions : Detailed information about the organization of lipids in fiber cell membranes of the human eye lens is necessary to explain the function of the fiber cell membranes in protecting the lens against cataract development. Information from EPR spin-labeling approaches, applied to study fiber cell membranes, contributes to a better understanding of the involvement of fiber cell membranes in eye lens heath and pathology.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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