Segments in the C-terminal folding domain of lipoprotein lipase important for binding to the low density lipoprotein receptor-related protein and to heparan sulfate proteoglycans.
Lipoprotein lipase (LpL) can mediate cellular uptake of chylomicron and VLDL remnants via binding to heparan sulfate proteoglycans (HSPG) and the endocytic alpha2-macroglobulin receptor/low density lipoprotein receptor-related protein (alpha2MR/LRP). Whereas it is established that the C-terminal folding domain binds to alpha2MR/LRP, it remains uncertain whether it binds to heparin and to HSPG. To identify segments important for binding to alpha2MR/LRP and to clarify possible binding to heparin, we produced constructs of the human C-terminal folding domain, LpL-(313-448), and of the fragment LpL-(347-448) in Escherichia coli. In addition to binding to alpha2MR/LRP, LpL-(313-448) displayed binding to heparin with an affinity similar to that of the LpL monomer, whereas it bound poorly to lipoprotein particles. Moreover, LpL-(313-448) displayed heparin sensitive binding to normal, but not to HSPG deficient Chinese hamster ovary cells. LpL-(313-448) and LpL-(347-448) showed similar affinities for binding to both purified alpha2MR/LRP and to heparin. Deletion of LpL residues 380-384 abolished the binding to LRP, whereas binding to heparin was unperturbed. The binding to both heparin and alpha2MR/LRP was essentially abolished following deletion of residues 404-430, and pretreatment of CHO cells with the peptide comprising aa 402-423 inhibited the binding of LpL-(313-448). We conclude that the C-terminal folding domain of human LpL has a site for binding to heparin and to HSPG, presumably involving amino acids within residues 404-430. Two segments of the domain are necessary for efficient binding to alpha2MR/LRP, one comprising residues 380-384 and another overlapping the segment important for binding to heparin.
Nielsen
M S
MS
Department of Medical Biochemistry, University of Aarhus, DK-8000 Aarhus C, Denmark.
Brejning
J
J
García
R
R
Zhang
H
H
Hayden
M R
MR
Vilaró
S
S
Gliemann
J
J
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D005343:Fibrinolytic Agents / Q000378:metabolism; D006493:Heparin / Q000378:metabolism; D006495:Heparin, Low-Molecular-Weight / Q000378:metabolism; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D018613:Microscopy, Confocal; D008958:Models, Molecular; D008970:Molecular Weight; D011487:Protein Conformation; D011971:Receptors, Immunologic / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism*; D000078222:Tinzaparin; D000511:alpha-Macroglobulins / Q000378:metabolism*
D005343:Fibrinolytic Agents; D006493:Heparin; D006495:Heparin, Low-Molecular-Weight; D006497:Heparan Sulfate; D008071:Lipoprotein Lipase; D008079:Lipoproteins, VLDL; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D000078222:Tinzaparin; D000511:alpha-Macroglobulins