title: Dynamics and heterogeneity of bovine hippocampal membranes: role of cholesterol and proteins.
abstract: The structural and dynamic consequence of alterations in membrane lipid composition (specifically cholesterol) in neuronal membranes is poorly understood. Previous work from our laboratory has established bovine hippocampal membranes as a convenient natural source for studying neuronal receptors. In this paper, we have explored the role of cholesterol and proteins in the dynamics and heterogeneity of bovine hippocampal membranes using fluorescence lifetime distribution analysis of the environment-sensitive fluorescent probe Nile Red incorporated into such membranes by the maximum entropy method (MEM), and time-resolved fluorescence anisotropy measurements. The peak position and the width of the lifetime distribution of Nile Red show a progressive reduction with increasing cholesterol depletion from native hippocampal membranes indicating that the extent of heterogeneity decreases with decrease in membrane cholesterol content. This is accompanied by a concomitant decrease of the fluorescence anisotropy and rotational correlation time. Our results point out that the microenvironment experienced by Nile Red is relatively insensitive to the presence of proteins in hippocampal membranes. Interestingly, Nile Red lifetime distribution in liposomes of lipid extracts is similar to that of native membranes indicating that proteins do not contribute significantly to the high level of heterogeneity observed in native membranes. These results could be relevant in understanding the neuronal diseases characterized by defective membrane lipid metabolism.
authors.affiliation: Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
authors.forename: Soumi
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Mamata
authors.initials: M
authors.lastname: Kombrabail
authors.forename: G
authors.initials: G
authors.lastname: Krishnamoorthy
authors.forename: Amitabha
authors.initials: A
authors.lastname: Chattopadhyay
mesh_terms: D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000502:physiology*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D007700:Kinetics; D008560:Membrane Fluidity / Q000502:physiology*; D008563:Membrane Lipids / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D044367:Phase Transition
chemical_list: D008563:Membrane Lipids; D009419:Nerve Tissue Proteins; D002784:Cholesterol