Title : Targeting of
neutral cholesterol ester hydrolase to the endoplasmic reticulum via its N-terminal
sequence
Abstract :
- Neutral cholesterol ester hydrolase ( NCEH ) accounts for a large part of the nCEH activity in macrophage foam cells, a hallmark of atherosclerosis, but its subcellular localization and structure-function relationship are unknown
- Here, we determined subcellular localization, glycosylation, and nCEH activity of a series of NCEH mutants expressed in macrophages
- NCEH is a single-membrane-spanning type II membrane protein comprising three domains: N-terminal, catalytic, and lipid-binding domains
- The N-terminal domain serves as a type II signal anchor sequence to recruit NCEH to the endoplasmic reticulum (ER) with its catalytic domain within the lumen
- All of the putative N-linked glycosylation sites ( Asn(270), Asn(367), and Asn(389) ) of NCEH are glycosylated
- Glycosylation at Asn(270) , which is located closest to the catalytic serine motif , is important for the enzymatic activity
- Cholesterol loading by incubation with acetyl-LDL does not change the ER localization of NCEH
- In conclusion, NCEH is targeted to the ER of macrophages, where it hydrolyzes CE to deliver cholesterol for efflux out of the cells