Esterification of side-chain oxysterols by lysosomal phospholipase A2

Akira Abe; Miki Hiraoka; Fumiko Matsuzawa; Sei-Ichi Aikawa; Youichi Niimura

doi:10.1016/j.bbalip.2020.158787

Esterification of side-chain oxysterols by lysosomal phospholipase A2

Biochim Biophys Acta Mol Cell Biol Lipids. 2020 Oct;1865(10):158787. doi: 10.1016/j.bbalip.2020.158787. Epub 2020 Aug 8.

Authors

Akira Abe¹, Miki Hiraoka², Fumiko Matsuzawa³, Sei-Ichi Aikawa³, Youichi Niimura⁴

Affiliations

¹ Department of Molecular Science of Bacteria, Tokyo University of Agriculture, Tokyo, Japan. Electronic address: aabe@umich.edu.
² Department of Ophthalmology, Health Science University of Hokkaido, Sapporo, Japan.
³ Altif Laboratories Inc., Tokyo, Japan.
⁴ Department of Molecular Science of Bacteria, Tokyo University of Agriculture, Tokyo, Japan.

PMID: 32777483
DOI: 10.1016/j.bbalip.2020.158787

Abstract

Side-chain oxysterols produced from cholesterol either enzymatically or non-enzymatically show various bioactivities. Lecithin-cholesterol acyltransferase (LCAT) esterifies the C3-hydroxyl group of these sterols as well as cholesterol. Lysosomal phospholipase A2 (LPLA2) is related to LCAT but does not catalyze esterification of cholesterol. First, esterification of side-chain oxysterols by LPLA2 was investigated using recombinant mouse LPLA2 and dioleoyl-PC/sulfatide/oxysterol liposomes under acidic conditions. TLC and LC-MS/MS showed that the C3 and C27-hydroxyl groups of 27-hydroxycholesterol could be individually esterified by LPLA2 to form a monoester with the C27-hydroxyl preference. Cholesterol did not inhibit this reaction. Also, LPLA2 esterified other side-chain oxysterols. Their esterifications by mouse serum containing LCAT supported the idea that their esterifications by LPLA2 occur at the C3-hydroxyl group. N-acetylsphingosine (NAS) acting as an acyl acceptor in LPLA2 transacylation inhibited the side-chain oxysterol esterification by LPLA2. This suggests a competition between hydroxycholesterol and NAS on the acyl-LPLA2 intermediate formed during the reaction. Raising cationic amphiphilic drug concentration or ionic strength in the reaction mixture evoked a reduction of the side-chain oxysterol esterification by LPLA2. This indicates that the esterification could progress via an interfacial interaction of LPLA2 with the lipid membrane surface through an electrostatic interaction. The docking model of acyl-LPLA2 intermediate and side-chain oxysterol provided new insight to elucidate the transacylation mechanism of sterols by LPLA2. Finally, exogenous 25-hydroxycholesterol esterification within alveolar macrophages prepared from wild-type mice was significantly higher than that from LPLA2 deficient mice. This suggests that there is an esterification pathway of side-chain oxysterols via LPLA2.

Keywords: Acyl-CoA:cholesterol acyltransferase; Esterification; Lecithin-cholesterol acyltransferase; Lysosomal phospholipase A2; Side-chain oxysterols; Transacylation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Catalysis
Cholesterol / metabolism*
Esterification / genetics
Humans
Hydroxycholesterols / metabolism
Lysosomes / enzymology
Macrophages / metabolism
Mice
Oxysterols / metabolism*
Phosphatidylcholine-Sterol O-Acyltransferase / genetics*
Phospholipases A2 / genetics*
Phospholipases A2 / metabolism
Sphingosine / analogs & derivatives
Sphingosine / metabolism

Substances

Hydroxycholesterols
N-acetylsphingosine
Oxysterols
27-hydroxycholesterol
25-hydroxycholesterol
Cholesterol
LCAT protein, human
Phosphatidylcholine-Sterol O-Acyltransferase
Phospholipases A2
Sphingosine