PMID: 17322565

 

    Legend: Sugar

Title : Glycosylation of endothelial lipase at asparagine-116 reduces activity and the hydrolysis of native lipoproteins in vitro and in vivo

Abstract :
  1. 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 asparagine-116 ( Asn-116 ) with alanine ( Ala ) (N116A) increased the hydrolytic activity of EL
  2. The current study demonstrates that mutagenesis of either Asn-116 to threonine ( Thr ) or Thr-118 to Ala also disrupted the glycosylation of EL and enhanced catalytic activity toward synthetic substrates by 3-fold versus wild-type EL
  3. Furthermore, we assessed the hydrolysis of native lipoprotein lipids by EL-N116A
  4. EL-N116A exhibited a 5-fold increase in LDL hydrolysis and a 1.8-fold increase in HDL2 hydrolysis
  5. Consistent with these observations, adenovirus-mediated expression of EL-N116A in mice significantly reduced the levels of both LDL and HDL cholesterol beyond the reductions observed by the expression of wild-type EL alone
  6. Finally, we introduced Asn-116 of EL into the analogous positions within LPL and HL, resulting in N-linked glycosylation at this site
  7. Glycosylation at this site suppressed the LPL hydrolysis of synthetic substrates, LDL, HDL2 , and HDL3 but had little effect on HL activity
  8. These data suggest that N-linked glycosylation at Asn-116 reduces the ability of EL to hydrolyze lipids in LDL and HDL2