Identification of Proteins That Interact with Acyl CoA:Diacylglycerol Acyltransferase (DGAT) Enzymes

Abstract

Triacylglycerols are the predominant storage form of energy in eukaryotes. As obesity has become a worldwide problem and excessive accumulation of triacylglycerols in adipose tissue causes obesity, enzymes catalyzing the synthesis of triacylglycerols are of great interest. Acyl CoA:diacylglycerol acyltransferase (DGAT), including the isoforms DGAT1 and DGAT2, catalyze the final and committed step in triacylglycerol synthesis. Proteins that physically interact with DGAT1 may provide information regarding the metabolic role of DGAT1. We chose HEK-293T cell line to express DGAT1 and used mass spectrometry to identify proteins that co-immunoprecipitated with DGAT1. We confirmed that DGAT2 and ACAT1 did interact with DGAT1. The interaction of DGAT1 with DGAT2 appeared to interrupt the synthesis of triacylglycerol since the co-expression of DGAT1 and DGAT2 was expected to increase triacylglycerol synthesis. This implied that DGAT1 and DGAT2 might serve different functional roles. On the other hand, DGAT1 overexpression may increase the synthesis of cholesterol esters that was the product of ACAT1. Additionally, ACAT1 overexpression did increase triacylglycerol synthesis and ACAT1 disruption by siRNA did decrease triacylglycerol synthesis. Our findings indicated that DGAT1 and ACAT1 might be involved in the same lipid-synthesizing protein complex.