Cloning of rabbit LCAT cDNA: increase in LCAT mRNA abundance in the liver of cholesterol-fed rabbits.

Abstract

Structure of rabbit lecithin:cholesterol acyltransferase (LCAT) and molecular basis for the effects of cholesterol feeding on LCAT expression were investigated by cloning and sequencing LCAT cDNA from rabbit. The rabbit and human sequences are 91% identical at the nucleotide level and 93% identical at the amino acid level. The interfacial substrate active site, asparagine-linked glycosylation sites, and sites at which rare mutations cause human familial LCAT deficiency are all highly conserved in the rabbit protein. The apparent molecular mass of rabbit LCAT, as determined by immunoblot analysis, was approximately equal to that of human LCAT. Rabbits showed 2.6- and 5.5-fold increases in serum LCAT activity 3 and 6 weeks, respectively, after switching to a cholesterol-enriched diet. Northern blot analysis revealed that the abundance of LCAT mRNA in liver increased 1.6- and 2.8-fold after 3 and 6 weeks, respectively, of cholesterol feeding. The marked temporal relation between the increase in serum LCAT activity and the liver LCAT mRNA abundance suggest that the regulation of LCAT activity in vivo may be primarily determined by changes in the amount of LCAT mRNA.