Figure 2.

Transport of intestinal cholesterol. This illustration summarizes the main steps involved in the uptake of cholesterol (C) from the lumen into the enterocyte, and the intracellular events that lead to the eventual incorporation of the cholesterol into nascent chylomicron (CM) particles. Here, Niemann-Pick C1 Like1 (NPC1L1) is depicted as the brush border membrane sterol transporter that facilitates the uptake of cholesterol and non-cholesterol sterols into the enterocyte. As discussed in the text, some studies suggest that other proteins might perform this function, and that NPC1L1 might instead be located at intracellular sites. Fatty acids (FA), which enter the cell through other mechanisms, are either incorporated into triacylglycerols (TG), or used to form cholesteryl esters (CE) through the action of acyl CoA: cholesterol acyltransferase 2 (ACAT2). Subsequently, the CE, as well as some unesterified cholesterol, along with TG and apolipoprotein B48 (apo B48), are packaged into nascent CM through the action of microsomal triglyceride transfer protein (MTP).