ACAT1, Cav-1, and PrP expression in brains and skin fibroblasts from Sarda breed sheep with scrapie-resistant and scrapie-susceptible genotype.

Abstract

Scrapie is an infective ovine neurodegenerative disease; the only identified component of the infectious agent being an aberrant isoform (PrPSc) of the cellular prion protein (PrPC). So far, no means for ante-mortem diagnosis are available for Scrapie as well as for any other mammal Transmissible Spongiform Encephalopaties. We recently found a strong relationship between cell susceptibility to scrapie-infection and intracellular cholesterol homeostasis alterations. In brain tissues as well as in ex vivo cultures of skin fibroblasts and PBMCs from healthy and scrapie-affected sheep carrying a scrapie-susceptible (ARQ/ARQ) genotype, the levels of cholesterol esters were consistently higher than in tissues and cultures derived from animals with a scrapie-resistant (ARR/ARR) genotype. Moreover, both uninfected and scrapie-affected ARQ/ARQ sheep showed abnormally low levels of high density lipoprotein-cholesterol (HDL-C) in their plasma, as compared to ARR/ARR animals. We now show that intracellular accumulation of cholesterol esters in fibroblasts derived from scrapie-susceptible sheep was accompanied by parallel alterations in the expression level of genes and gene products (ACAT1 and Cav-1) that are involved in the pathways leading to intracellular cholesterol esterification and trafficking. Comparative analysis of PrPc mRNA, showed an higher expression level in cells from animals carrying susceptible genotype, with or without Scrapie. Preliminary experiments also revealed the presence of PK-resistant PrP isoforms in the latter cultures. The data reported in the present paper suggest that accumulation of cholesterol esters in peripheral cells, together with the altered expression of some proteins implicated in intracellular cholesterol homeostasis, might serve to identify a distinctive lipid metabolic profile associated with increased susceptibility to develop prion disease following infection.