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Papers In Press, published online ahead of print February 24, 2007
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Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
Corresponding Author: robbrown{at}mail.med.upenn.edu
We previously identified that four of five putative N-linked glycosylation sites of human endothelial lipase (EL) are utilized, and suggested that the substitution of Asn-116 with Ala (N116A) increased the hydrolytic activity of EL. The current study demonstrates that mutagenesis of either Asn-116 to Thr or Thr-118 to Ala also disrupted glycosylation of EL and enhanced catalytic activity toward synthetic substrates by 3-fold versus wild-type EL. Furthermore, we assessed the hydrolysis of native lipoprotein lipids by EL-N116A. EL-N116A exhibited a 5-fold increase in low density lipoprotein (LDL) hydrolysis and a 1.8-fold increase in high density lipoprotein (HDL) 2 hydrolysis. Consistent with these observations, adenoviral-mediated expression of EL-N116A in mice significantly reduced levels of both LDL and HDL cholesterol beyond the reductions observed by the expression of wild-type EL alone. Finally, we introduced Asn-116 of EL into the analogous positions within lipoprotein lipase (LPL) and hepatic lipase (HL), resulting in N-linked glycosylation at this site. Glycosylation at this site suppressed LPL hydrolysis of synthetic substrates, LDL, HDL2, and HDL3, but had little effect on HL activity. These data suggest that N-linked glycosylation at Asn-116 reduces the ability of EL to hydrolyse lipids in LDL and HDL2.
Revised on February 9, 2007
Accepted on February 23, 2007
Glycosylation of endothelial lipase at asparagine-116 reduces activity and hydrolysis of native lipoproteins in vitro and in vivo
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