May 2007
Volume 48, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2007
Caveolin-1 Is Mainly a Peripheral Membrane Protein in Bovine Lens Epithelial Cells and in Bovine Liver and Apipose Tissue
Author Affiliations & Notes
  • R. Cenedella
    Dept of Biochemistry, A.T. Still Univ of Hlth Sciences, Kirksville, Missouri
  • P. S. Sexton
    Dept of Biochemistry, A.T. Still Univ of Hlth Sciences, Kirksville, Missouri
  • R. F. Jacob
    Elucida Research, Elucida Research/Beverky, Massachusetts
  • L. Brako
    Dept of Anatomy and Neurobiology,
    Moorehouse School of Medicine, Atlanta, Georgia
  • W.-K. Lo
    Dept of Anatomy and Neurobiology,
    Moorehouse School of Medicine, Atlanta, Georgia
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 4216. doi:
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      R. Cenedella, P. S. Sexton, R. F. Jacob, L. Brako, W.-K. Lo; Caveolin-1 Is Mainly a Peripheral Membrane Protein in Bovine Lens Epithelial Cells and in Bovine Liver and Apipose Tissue. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4216.

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

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Abstract

Purpose:: Our goal was to describe the distribution and relative concentration of caveolin-1 in fractions of bovine lens epithelial and fiber cells. A new concept is reported: caveolin-1 may be mainly a peripheral membrane protein in some cells. Caveolin-1 is typically viewed as a scaffolding protein for caveolae in plasma membrane.

Methods:: Crude membrane from cultured bovine lens epithelial cells, lens fiber cells, and bovine liver and adipose tissue were divided into urea soluble (7M urea) and insoluble fractions. Cytosolic lipid vesicles were also recovered from the lens epithelial cells. Lipid-raft domains of fiber cell membrane were recovered following treatment with detergents. Aliquots of all fraction were Western blotted for caveolin-1. Fluorescence microscopy and double immunofluorescence labeling was used to examine the distribution of caveolin-1 in lipid vesicles and cultured epithelial cells.

Results:: Caveolin-1 appears to largely be plasma membrane associated in cultured bovine lens epithelial cells. Fluorescence labeling identified caveolin-1 in plasma membrane, but not in endoplasmic reticulum. Abundant caveolae were seen in electron micrographs of plasma membrane in lens epithelial cells. About 60% of the caveolin-1 in the epithelial cells was soluble in 7M urea, a characteristic of peripheral membrane proteins. About 30 % of the total was urea-insoluble intrinsic protein. The remainder was present in cytoplasmic lipid vesicles. Caveolin-1 was also mainly a peripheral protein in liver and adipose tissue membrane fractions. By contrast, caveolin was mainly intrinsic protein in the lens fiber cell membrane, being present at relatively low concentrations in caveolae-free lipid raft domains.

Conclusions:: Depending on the cell type, cellular caveolin-1 can mainly be peripheral membrane protein which perhaps binds to membrane through interaction with integral caveolin-1.

Keywords: cell membrane/membrane specializations • gap junctions/coupling • lipids 
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