LIPOPROTEIN LIPASE-ENHANCED BINDING OF HUMAN TRIGLYCERIDE-RICH LIPOPROTEINS TO HEPARAN-SULFATE - MODULATION BY APOLIPOPROTEIN-E AND APOLIPOPROTEIN-C

The objective of this study was to investigate whether compositional v ariation in apolipoprotein (ape) content of triglyceride-rich lipoprot eins (TRLP) modulates binding of heparan sulfate proteoglycans (HSPG). Human TRLP was enriched with apoE and apoCs and the ability to bind b iotin-conjugated heparan sulfate (b-HS) was studied in the presence or absence of heat-inactivated lipoprotein lipase (LPL). TRLP, associate d with LPL, showed an increased capacity to bind b-HS compared with TR LP alone. Low density lipoproteins (LDL) bound both b-HS and LPL with a higher affinity than TRLP. ApoE enrichment of TRLP resulted in an en hanced binding of b-HS. Increased binding of b-HS to TRLP by the combi nation of apoE enrichment and LPL addition was found to be complementa ry, not affecting their individual binding capacity. TRLP enrichment w ith apoC led to the formation of an apoC-rich, apoE-poor particle; thi s alteration by itself did not change the ability to bind b-HS. ApoC e nrichment of TRLP resulted in a reduced capacity to bind LPL and there fore a subsequently reduced capacity to bind b-HS, compared with contr ol TRLP associated with LPL. Competition studies revealed that b-HS bi nding to TRLP was fully displaceable by lactoferrin but barely by hepa ran sulfate, dermatan sulfate, or chondroitin-4-sulfate. Using TRLP co ated to microtiter wells and associated with LPL, the b-HS displacemen t patterns were comparable to those obtained with coated LDL in the pr esence or absence of LPL. The cell-free system that was used enabled u s to identify the functions of apoC and apoE in the binding of TRLP to LPL and HSPG. Both LPL and apoE increased the ability of TRLP to bind HSPG. The apoC content of TRLP regulated the docking of TRLP to LPL. ApoC enrichment reduced the affinity or capacity of TRLP to LPL bindin g, and this has relevance for the lipolytic cascade.-van Barlingen, H. H. J. J., H. de Jong, D. W. Erkelens, and T. W. A. de Bruin. Lipoprot ein lipase-enhanced binding of human triglyceriderich lipoproteins to heparan sulfate: modulation by apolipoprotein E and apolipoprotein C.