Decreased membrane fluidity and unsaturated fatty acids in Niemann–Pick disease type C fibroblasts

Abstract

Niemann-Pick disease type C (NP-C) is an autosomal recessive disorder characterized by the sequestration and trapping of endocytosed cholesterol in lysosomes. The NPC1 gene on chromosome 18 was recently identified but its physiological function remains unknown. We have studied the lipid compositions of cultured human NP-C fibroblasts and mouse SPM-3T3 cell line derived from the C57BL/KsJ NP-C model mouse, which belongs to the same complementation group. Fibroblasts derived from apparently normal age-matched individuals and a subline of SPM-3T3 cells which restores cholesterol metabolism by transfer of human chromosome 18 were used as controls. Levels of free cholesterol in whole cell homogenates increased about 1.5-fold in human NP-C fibroblasts and mouse SPM-3T3 cells, while in the plasma membrane, cholesterol content did not significantly change in NP-C fibroblasts but rather decreased in SPM-3T3 cells. The total phospholipid content did not significantly change; however, among phospholipid head groups, increases in sphingomyelin and decreases in other classes were observed in human NP-C fibroblasts and mouse SPM-3T3 cells. The ratios of saturated fatty acids to unsaturated fatty acids increased in both human and mouse cells. The increase was also confirmed in the plasma membrane fraction of SPM-3T3 cells. Membrane fluidity was examined using a 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescent probe. The DPH anisotropy values were markedly increased in NP-C fibroblasts and in SPM-3T3 cells. The results suggest that a NP-C mutation causes complex alterations in cellular lipid contents and biophysical properties of the membrane.

Plasma Membrane Cholesterol Content Affects Nitric Oxide Diffusion Dynamics and Signaling

“…Niemann-Pick C1, Normal Human Fibroblasts, and Methyl-␤-cyclodextrin Depletion/Repletion as a Model System for Altering Cellular Cholesterol Plasma Membrane Content-NPC1 fibroblasts have been shown to exhibit a marked increase in plasma membrane cholesterol content (16) and decreased membrane fluidity relative to normal human fibroblasts (16,17). Consistent with these reports, plasma membranes isolated from NPC1 fibroblasts were found to contain ϳ2-fold higher total cholesterol content relative to NHF, whereas a similar level of resident proteins (data not shown) and phospholipid content was present in both cell types (Fig.…”

“…Within the plasma membrane, cholesterol segregated with sphingolipids and selective proteins form distinct lipid raft complexes that act as ordered platforms for communicating signals into and out of cells (12). Dysregulation of cholesterol synthesis and transport acts as a contributing factor to pathophysiological changes (13)(14)(15)(16)(17), which are of particular importance in cardiovascular disease, chronic inflammation, and lipid disorders such as NiemannPick disease. The influence of cholesterol on NO diffusion was directly quantified in liposomal and artificial bilayer preparations.…”

Caveolin-associated Accumulation of Globotriaosylceramide in the Vascular Endothelium of α-Galactosidase A Null Mice

“…The increased cholesterol impaired insulin signaling and was restored following cholesterol depletion (24). In other studies cholesterol levels have been reported to be increased, decreased, or unchanged (25)(26)(27)(28).…”

Sphingolipids and membrane biology as determined from genetic models

“…Rhodopsin (Rh1) is required not only for transducing the light signal in the adult retina but also for stabilizing the actin-based cytoskeletal scaffold of developing photoreceptors, which is called the rhabdomere terminal web (RTW). In ninaE 117 mutants, which lack Rh1, the RTW is not organized and rhabdomere biogenesis is defective. Newly eclosed flies show inappropriately formed rhabdomeric components that involute into the cytosol [62].…”

“…Tissues derived from these mice show increased sphingomyelin content and increased ratios of saturated fatty acid to unsaturated fatty acids. These effects are accompanied by decreased plasma membrane fluidity [117].…”