title: Expression of human hepatic lipase negatively impacts apolipoprotein A-I production in primary hepatocytes from Lipc-null mice.
abstract: This study aimed to examine whether expression of human hepatic lipase (hHL) exerted an intracellular effect on hepatic production of apolipoprotein (apo) A-I. The levels of secreted and cell-associated apoA-I were contrasted between primary hepatocytes isolated from Lipc-null and C57BL/6 mice, and between Lipc-null hepatocytes transfected with either hHL-encoding or control adenovirus. An HSPG-binding deficient hHL protein (hHLmt) was used to determine the impact of cell surface binding on HL action. Accumulation of apoA-I in conditioned media of primary hepatocytes isolated from Lipc-null mice was increased as compared to that from C57BL/6 mice. Metabolic labeling experiments showed that secretion of (35)S-apoA-I from Lipc-null cells was significantly higher than that from C57BL/6 cells. Expression of hHL in Lipc-null hepatocytes, through adenovirus-mediated gene transfer, resulted in decreased synthesis and secretion of (35)S-apoA-I, but not (35)S-apoE, as compared with cells transfected with control adenovirus. Expression of HSPG-binding deficient hHLmt in Lipc-null cells also exerted an inhibitory effect on apoA-I production, even though hHLmt displayed impaired exit from the endoplasmic reticulum as compared with hHL. Subcellular fractionation revealed that expression of hHL or hHLmt led to increased microsome-association of apoA-I relative to non-transfected control. Expression of hHL negatively impacts hepatic production of apoA-I.
authors.affiliation: Department of Biochemistry, Microbiology & Immunology, and ; Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada; ; Human Health Therapeutics Portfolio, Life Sciences Division, National Research Council Canada, Ottawa, Ontario, K1A 0R6, Canada;
authors.forename: Michelle
authors.initials: M
authors.lastname: Bamji-Mirza
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada; ; Human Health Therapeutics Portfolio, Life Sciences Division, National Research Council Canada, Ottawa, Ontario, K1A 0R6, Canada;
authors.forename: Wandong
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, Microbiology & Immunology, and ; Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, K1H 8M5, Canada.
authors.forename: Zemin
authors.initials: Z
authors.lastname: Yao
keywords: ABCA1; adenovirus; endoplasmic reticulum; heparan sulphate proteoglycans; high density lipoprotein