Membrane Anomalies in Huntington's Disease Fibroblasts

Publisher Website
Google Scholar
Abstract
Plasma membranes, microsomes and mitochondria were isolated from paired, passage number matched, cultured human fibroblasts. The cells were obtained from skin biopsies of Huntington''s disease (HD) subjects and from sex and age matched controls. All fibroblasts were cultured in identical media for 3-7 passages. Enrichment of surface marker enzymes such as Na+,K+-ATPase indicated a 10-fold purification of the isolated plasma membrane. The specific activity of Na+,K+-ATPase was 62 and 82% greater in the crude homogenate and isolated plasma membrane, respectively, of HD fibroblasts than in control fibroblasts. The specific activity of plasma membrane Na+,K+-ATPase was correlated with lipid composition and with membrane structure as determined by measurement of the rotational relaxation time and limiting anisotropy of fluorescence probe molecules. Major alterations in the structure of the plasma membranes in HD fibroblasts were not noted. The rotational relaxation time and limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene and of trans-parinaric acid were not significantly different between the plasma membrane, microsomes or mitochondria of HD verus those of control fibroblasts. trans-Parinaric acid demonstrated the coexistence of fluid and solid domains in all 3 subcellular membrane fractions of the normal and HD skin fibroblasts. Both trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene displayed characteristic breakpoints in Arrhenius plots of absorbance corrected fluorescence in plasma membranes, microsomes and mitochondria. In all cases, similar breakpoint temperatures, indicative of phase alterations, were noted near 20.degree. and 30.degree. C. These breakpoints were unaltered in HD. The data do not support the concept of major membrane structural defects in HD.