Immunodepletion experiments suggest that acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) protein plays a major catalytic role in adult human liver, adrenal gland, macrophages, and kidney, but not in intestines

Abstract

The first acyl-coenzyme A:cholesterol acyltransferase (ACAT) cDNA cloned and expressed in 1993 is designated as ACAT-1. In various human tissue homogenates, ACAT-1 protein is effectively solubilized with retention of enzymatic activity by the detergent CHAPS along with high salt. After using anti-ACAT-1 antibodies to quantitatively remove ACAT-1 protein from the solubilized enzyme, measuring the residual ACAT activity remaining in the immunodepleted supernatants allows us to assess the functional significance of ACAT-1 protein in various human tissues. The results showed that ACAT activity was immunodepleted 90% in liver (83% in hepatocytes), 98% in adrenal gland, 91% in macrophages, 80% in kidney, and 19% in intestines, suggesting that ACAT-1 protein plays a major catalytic role in all of the human tissue/cell homogenates examined except intestines. Intestinal ACAT activity is largely resistant to immunodepletion and is much more sensitive to inhibition by the ACAT inhibitor Dup 128 than liver ACAT activity.—Lee, O., C. C. Y. Chang, W. Lee, and T-Y. Chang. Immunodepletion experiments suggest that acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) protein plays a major catalytic role in adult human liver, adrenal gland, macrophages, and kidney, but not in intestines.

Keywords

• cholesteryl esters
• hepatocytes
• membrane protein solubilization
• detergents