Equivalent binding of wild-type lipoprotein lipase (LPL) and S447X-LPL to GPIHBP1, the endothelial cell LPL transporter.
The S447X polymorphism in lipoprotein lipase (LPL), which shortens LPL by two amino acids, is associated with low plasma triglyceride levels and reduced risk for coronary heart disease. S447X carriers have higher LPL levels in the pre- and post-heparin plasma, raising the possibility that the S447X polymorphism leads to higher LPL levels within capillaries. One potential explanation for increased amounts of LPL in capillaries would be more avid binding of S447X-LPL to GPIHBP1 (the protein that binds LPL dimers and shuttles them to the capillary lumen). This explanation seems plausible because sequences within the carboxyl terminus of LPL are known to mediate LPL binding to GPIHBP1. To assess the impact of the S447X polymorphism on LPL binding to GPIHBP1, we compared the ability of internally tagged versions of wild-type LPL (WT-LPL) and S447X-LPL to bind to GPIHBP1 in both cell-based and cell-free binding assays. In the cell-based assay, we compared the binding of WT-LPL and S447X-LPL to GPIHBP1 on the surface of cultured cells. This assay revealed no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1. In the cell-free assay, we compared the binding of internally tagged WT-LPL and S447X-LPL to soluble GPIHBP1 immobilized on agarose beads. Again, no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1 were observed. We conclude that increased binding of S447X-LPL to GPIHBP1 is unlikely to be the explanation for more efficient lipolysis and lower plasma triglyceride levels in S447X carriers.
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Kirsten
K
Turlo
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Calvin S
CS
Leung
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Jane J
JJ
Seo
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Chris N
CN
Goulbourne
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Oludotun
O
Adeyo
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Peter
P
Gin
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Constance
C
Voss
Division of Nutritional Science, Cornell University, Ithaca, NY 14853, United States.
André
A
Bensadoun
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States.
Loren G
LG
Fong
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States; Department of Human Genetics, University of California, Los Angeles, CA 90095, United States. Electronic address: sgyoung@mednet.ucla.edu.
Stephen G
SG
Young
Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, United States. Electronic address: abeigneux@mednet.ucla.edu.
Anne P
AP
Beigneux
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001681:Biological Assay; D016466:CHO Cells; D003412:Cricetulus; D015870:Gene Expression; D006801:Humans; D055767:Immobilized Proteins / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D011485:Protein Binding; D021381:Protein Transport; D018110:Receptors, Lipoprotein / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
C523701:GPIHBP1 protein, human; D055767:Immobilized Proteins; D018110:Receptors, Lipoprotein; D011993:Recombinant Fusion Proteins; D014280:Triglycerides; C548261:LPL protein, human; D008071:Lipoprotein Lipase
GPIHBP1; Lipoprotein lipase; Triglyceride metabolism