CLONING AND EXPRESSION IN XENOPUS OOCYTES OF A MOUSE HOMOLOG OF THE HUMAN ACYLCOENZYME-A - CHOLESTEROL ACYLTRANSFERASE AND ITS POTENTIAL ROLE IN METABOLISM OF OXIDIZED LDL

We used a Xenopus oocyte expression system to screen a mouse macrophag e cDNA library for receptors for oxidized LDL (OxLDL). Injection of un fractionated mouse macrophage mRNA induced OxLDL binding activity on o ocytes. An excess of acetylated LDL (AcLDL) inhibited the binding of O xLDL by only 30%, indicating the expression of OxLDL receptors distinc t from the scavenger receptor (SRA). The library was screened and anal yzed by competition binding using [I-125]OxLDL and AcLDL, to avoid clo ning of SRA. One of the purified clones encoded a peptide with 85% ide ntity with human acyl-coenzyme A:cholesterol acyltransferase (ACAT). I njection of ACAT mRNA into oocytes induced specific binding of OxLDL. ACAT is expressed in mouse macrophages as a similar to 3.6 kB transcri pt and the expression is upregulated in human THP-1 cells treated with PMA. (C) 1996 Academic Press, Inc.