C-terminal His6-tagged lecithin-cholesterol acyltransferase (LCAT) is catalytically active

Construction and characterization of polycistronic retrovirus vectors for sustained and high-level co-expression of apolipoprotein A-I and lecithin-cholesterol acyltransferase

Apolipoprotein A-I (apo A-I) and lecithin-cholesterol acyltransferase (LCAT) are constituents of circulating high-density lipoprotein (HDL) particles and play an important role in 'reverse cholesterol transport', the process by which cholesterol in peripheral tissues is transferred to the liver for excretion. Enhancing levels of apo A-I, as well as LCAT, in plasma may promote the removal of excess cholesterol from the arterial wall and thus reduce the formation of atherosclerotic lesions. Indeed, both apo A-I and LCAT genes have been identified as therapeutic targets to prevent or limit atherogenesis. Here, we have constructed two retroviral vectors, one containing LCAT cDNA and the neomycin phosphotransferase (NEO) gene (pLLEN), the other apo A-I cDNA, LCAT cDNA and the NEO gene (pLAPLEN) linked by internal ribosome entry sites (IRES). Both bi- and tricistronic retroviral vectors efficiently co-expressed their two or three genes when transfected into cultured mouse C2C12 muscle cells or human 293 cells. After 30 days, the retroviral vector sequences were retained by the host cells, whereas those of a conventional plasmid vector were lost. Moreover, transduced C2C12 mouse myoblasts maintained the ability for heterologous expression of human LCAT and apo A-I even after differentiation into myotubes. Stably-transduced clones of C2C12 cells were selected by neomycin (G418) resistance and continued to efficiently express human LCAT for 60 days. These findings indicate that the use of polycistronic retrovirus vectors to genetically modify myoblasts, which can be transplanted back into skeletal muscle, might be a safe and feasible strategy to express human apo A-I and LCAT and hence have therapeutic potential to regress atherosclerotic lesions.

Effects of peroxynitrite on plasma components of the reverse cholesterol transport pathway

Elimination of cholesterol from arterial tissue, crucial in limiting atherogenesis, may be achieved via high-density lipoprotein (HDL)-mediated reverse cholesterol transport (RCT); components of this pathway can be modulated by oxidative stress. Here we have examined the relations between cholesterol efflux, esterification and transfer in human plasma treated with the powerfully reactive nitrogen species, peroxynitrite. Cellular cholesterol efflux to whole plasma, or to peroxynitrite-modified HDL3, was relatively insensitive to peroxynitrite, as was the transfer of esterified cholesterol. However, plasma cholesterol esterification, via lecithin:cholesterol acyltransferase (LCAT), was markedly inhibited, both directly and indirectly, by peroxynitrite treatment, implying inefficient RCT follows HDL sequestration of cellular cholesterol.