摘要
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-nuW and C57BL/6 mice,and between Lipc-nuW 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-nuW mice was increased as compared to that from C57BL/6 mice.Metabolic labeling experiments showed that secretion of ＇＇S-apoA-I from Lipc-nuW cells was significantly higher than that from C57BL/6 cells.Expression of hHL in Lipc-nuW hepatocytes,through adenovirus-mediated gene transfer,resulted in decreased synthesis and secretion of ＇S-apoA-I,but not S-apoE,as compared with cells transfected with control adenovirus.Expression of HSPG-binding deficient hHLmt in Lipc-nuW 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.
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-nuW and C57BL/6 mice,and between Lipc-nuW 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-nuW mice was increased as compared to that from C57BL/6 mice.Metabolic labeling experiments showed that secretion of ＇＇S-apoA-I from Lipc-nuW cells was significantly higher than that from C57BL/6 cells.Expression of hHL in Lipc-nuW hepatocytes,through adenovirus-mediated gene transfer,resulted in decreased synthesis and secretion of ＇S-apoA-I,but not S-apoE,as compared with cells transfected with control adenovirus.Expression of HSPG-binding deficient hHLmt in Lipc-nuW 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.
基金
supported by a grant-in-aid (#T6903) from the Heart and Stroke Foundation of Ontario
