HDL biology
ApoA-IV activates CETP lipid transfer as effectively as apoA-I, binding lipid emulsions with similar affinity (Biochim Biophys Acta 1996)
Original title: Activation of human plasma cholesteryl ester transfer protein by human apolipoprotein A-IV
The role of apolipoprotein A-IV in activating CETP-mediated lipid transfer between lipid microemulsions was studied and compared with apoA-I. CETP showed little lipid transfer activity without bound apolipoproteins, but apoA-IV bound to the emulsion surface with an affinity similar to other helical apolipoproteins and activated CETP-mediated transfer of cholesteryl ester, triacylglycerol, and phosphatidylcholine, with cholesteryl ester and triacylglycerol transfer rates directly proportional to the amount of bound apoA-IV. Phosphatidylcholine activation was less effective until apoA-IV occupied 40% of the total lipid binding capacity of the emulsion. When cholesteryl ester and triacylglycerol were both present in the emulsion core, CETP strongly preferred transferring cholesteryl ester, but when the core contained only triacylglycerol, CETP transferred it at a rate similar to cholesteryl ester transfer. These findings for apoA-IV closely paralleled those previously observed for apoA-I and other amphiphilic helical apolipoproteins including apoA-II, apoE, and apoC-III.
Original abstract
Function of apolipoprotein (apo) A-IV was studied for its role in cholesteryl ester transfer protein (CETP; lipid transfer protein, LTP) reaction between lipid microemulsions having the diameter of low density lipoprotein, being compared to apoA-I. CETP hardly catalyzed lipid transfer without apolipoproteins. ApoA-IV bound to the surface of the microemulsion in equilibrium with a similar affinity to that of other helical apolipoproteins, and activated the transfer reaction by CETP of cholesteryl ester, triacylglycerol and phosphatidylcholine between the emulsions. The rate of the transfer reaction of cholesteryl ester and triacylglycerol was directly proportional to the amount of the bound apoA-IV to the surface of the emulsion. For phosphatidylcholine, activation was less effective until 40% of total binding capacity of lipid emulsion was occupied by the apolipoprotein. Cholesteryl ester was highly preferred by CETP over triacylglycerol when equal amount of these lipids was present in the core of the apoA-IV-activated emulsion, resulting in almost no triacylglycerol transfer. However, when the emulsion has the core exclusively of triacylglycerol, triacylglycerol was transferred by CETP with the rate in the same order as that of cholesteryl ester transfer. These findings were all comparable to the results with apoA-I, and also consistent with our previous observation for other amphiphilic helical apolipoproteins such as apoA-II, E and C-III.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 19 August 2026. Methods.