Transport of Lipoprotein Lipase Across Endothelial Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 6; pp. 2254 - 2258
• Main Authors: Saxena, Uday, Klein, Michael G., Goldberg, Ira J.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15-03-1991; National Acad Sciences
• Subjects: 550201 - Biochemistry- Tracer Techniques; Adipocytes; ADIPOSE TISSUE; ANIMAL TISSUES; Animals; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; Biological and medical sciences; Biological Transport - drug effects; BODY; CARBOXYLESTERASES; CARBOXYLIC ACIDS; Cattle; CELL CONSTITUENTS; CELL MEMBRANES; Cell physiology; Cells, Cultured; CONNECTIVE TISSUE; DAYS LIVING RADIOISOTOPES; Dextrans; DOSE-RESPONSE RELATIONSHIPS; ELECTRON CAPTURE RADIOISOTOPES; ELECTROPHORESIS; Endothelial cells; ENDOTHELIUM; Endothelium, Vascular - metabolism; ENZYMES; ESTERASES; Female; Fundamental and applied biological sciences. Psychology; Heparan sulfate proteoglycans; Heparin; HYDROLASES; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE 125; IODINE ISOTOPES; ISOTOPES; Kinetics; LABELLED COMPOUNDS; LIPASES; LIPIDS; lipoprotein lipase; Lipoprotein Lipase - isolation & purification; Lipoprotein Lipase - metabolism; LIPOPROTEINS; Membrane and intracellular transports; MEMBRANE TRANSPORT; MEMBRANES; Milk - enzymology; Molecular and cellular biology; MONOCARBOXYLIC ACIDS; Nonesterified fatty acids; NUCLEI; ODD-EVEN NUCLEI; OLEIC ACID; Oleic Acids - pharmacology; ORGANIC ACIDS; ORGANIC COMPOUNDS; PROTEINS; Radioactive decay; RADIOISOTOPES; Serum Albumin, Bovine - pharmacology; Sulfates; TISSUES; Ungulates; UPTAKE; Intracellular transport; Endothelial cell; Bovine; Enzyme; Lipoprotein lipase; Triglyceride; Fatty acids; Cell surface; Vertebrata; Regulation(control); Mammalia; Enzymatic activity; Internalization; Aorta; Glycosaminoglycan; Artiodactyla; Ungulata
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.6.2254

Lipoprotein lipase (LPL), synthesized in muscle and fat, hydrolyzes plasma triglycerides primarily while bound to luminal endothelial cell surfaces. To obtain information about the movement of LPL from the basal to the luminal endothelial cell surface, we studied the transport of purified bovine milk LPL across bovine aortic endothelial cell monolayers.125I-labeled LPL (125I-LPL) added to the basal surface of the monolayers was detected on the apical side of the cells in two compartments: (i) in the medium of the upper chamber, and (ii) bound to the apical cell surface. The amount of125I-LPL on the cell surface, but not in the medium, reached saturation with time and LPL dose. Catalytically active LPL was transported to the apical surface but very little LPL activity appeared in the medium. Heparinase treatment of the basal cell surface and addition of dextran sulfate (0.15 μ M) to the lower chamber decreased the amount of125I-LPL appearing on the apical surface. Similarly, the presence of increasing molar ratios of oleic acid/bovine serum albumin at the basal surface decreased the transport of active LPL across the monolayer. Thus, a saturable transport system, which requires heparan sulfate proteoglycans and is inhibited by high concentrations of free fatty acids on the basal side of the cells, appears to exist for passage of enzymatically active LPL across endothelial cells. We postulate that regulation of LPL transport to the endothelial luminal surface modulates the physiologically active pool of LPL in vivo.