An LPL-specific monoclonal antibody, 88B8, that abolishes the binding of LPL to GPIHBP1.

LPL contains two principal domains: an amino-terminal catalytic domain (residues 1-297) and a carboxyl-terminal domain (residues 298-448) that is important for binding lipids and binding glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1) (an endothelial cell protein that shuttles LPL to the capillary lumen). The LPL sequences required for GPIHBP1 binding have not been examined in detail, but one study suggested that sequences near LPL's carboxyl terminus (residues ∼403-438) were crucial. Here, we tested the ability of LPL-specific monoclonal antibodies (mAbs) to block the binding of LPL to GPIHBP1.

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).

Discovery of new liver X receptor agonists by pharmacophore modeling and shape-based virtual screening.

Agonists of liver X receptors (LXR) α and β are important regulators of cholesterol metabolism, but agonism of the LXRα subtype appears to cause hepatic lipogenesis, suggesting LXRβ-selective activators are attractive new lipid lowering drugs. In this work, pharmacophore modeling and shape-based virtual screening were combined to predict new LXRβ-selective ligands. Out of the 10 predicted compounds, three displayed significant LXR activity.

Chylomicronemia mutations yield new insights into interactions between lipoprotein lipase and GPIHBP1.

Lipoprotein lipase (LPL) is a 448-amino-acid head-to-tail dimeric enzyme that hydrolyzes triglycerides within capillaries. LPL is secreted by parenchymal cells into the interstitial spaces; it then binds to GPIHBP1 (glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1) on the basolateral face of endothelial cells and is transported to the capillary lumen. A pair of amino acid substitutions, C418Y and E421K, abolish LPL binding to GPIHBP1, suggesting that the C-terminal portion of LPL is important for GPIHBP1 binding.

GPIHBP1, an endothelial cell transporter for lipoprotein lipase.

Interest in lipolysis and the metabolism of triglyceride-rich lipoproteins was recently reignited by the discovery of severe hypertriglyceridemia (chylomicronemia) in glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1)-deficient mice. GPIHBP1 is expressed exclusively in capillary endothelial cells and binds lipoprotein lipase (LPL) avidly. These findings prompted speculation that GPIHBP1 serves as a binding site for LPL in the capillary lumen, creating "a platform for lipolysis.

Mutations in lipoprotein lipase that block binding to the endothelial cell transporter GPIHBP1.

GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells, shuttles lipoprotein lipase (LPL) from subendothelial spaces to the capillary lumen. An absence of GPIHBP1 prevents the entry of LPL into capillaries, blocking LPL-mediated triglyceride hydrolysis and leading to markedly elevated triglyceride levels in the plasma (i.e.

Assessing the role of the glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) three-finger domain in binding lipoprotein lipase.

Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) is an endothelial cell protein that transports lipoprotein lipase (LPL) from the subendothelial spaces to the capillary lumen. GPIHBP1 contains two main structural motifs, an amino-terminal acidic domain enriched in aspartates and glutamates and a lymphocyte antigen 6 (Ly6) motif containing 10 cysteines. All of the cysteines in the Ly6 domain are disulfide-bonded, causing the protein to assume a three-fingered structure.

Binding preferences for GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells.

Objective: To define the ability of GPIHBP1 to bind other lipase family members and other apolipoproteins (apos) and lipoproteins.

Methods And Results: GPIHBP1, a GPI-anchored lymphocyte antigen (Ly)6 protein of capillary endothelial cells, binds lipoprotein lipase (LPL) avidly, but its ability to bind related lipase family members has never been evaluated. As judged by cell-based and cell-free binding assays, LPL binds to GPIHBP1, but other members of the lipase family do not.

Unexpected expression pattern for glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) in mouse tissues revealed by positron emission tomography scanning.

Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), a GPI-anchored endothelial cell protein, binds lipoprotein lipase (LPL) and transports it into the lumen of capillaries where it hydrolyzes triglycerides in lipoproteins. GPIHBP1 is assumed to be expressed mainly within the heart, skeletal muscle, and adipose tissue, the sites where most lipolysis occurs, but the tissue pattern of GPIHBP1 expression has never been evaluated systematically. Because GPIHBP1 is found on the luminal face of capillaries, we predicted that it would be possible to define GPIHBP1 expression patterns with radiolabeled GPIHBP1-specific antibodies and positron emission tomography (PET) scanning.

Cholesterol intake modulates plasma triglyceride levels in glycosylphosphatidylinositol HDL-binding protein 1-deficient mice.

Objective: To determine whether plasma triglyceride levels in adult Glycosylphosphatidylinositol HDL-binding protein 1 (GPIHBP1)-deficient (Gpihbp1(-/-)) mice would be sensitive to cholesterol intake.

Methods And Results: Gpihbp1(-/-) mice were fed a Western diet containing 0.15% cholesterol.

Orchestration of concurrent oxidation and reduction cycles for stereoinversion and deracemisation of sec-alcohols.

Black and white are opposites as are oxidation and reduction. Performing an oxidation, for example, of a sec-alcohol and a reduction of the corresponding ketone in the same vessel without separation of the reagents seems to be an impossible task. Here we show that oxidative cofactor recycling of NADP (+) and reductive regeneration of NADH can be performed simultaneously in the same compartment without significant interference.

Biocatalytic racemization of sec-alcohols and alpha-hydroxyketones using lyophilized microbial cells.

Biocatalytic racemization of aliphatic and aryl-aliphatic sec-alcohols and alpha-hydroxyketones (acyloins) was accomplished using whole resting cells of bacteria, fungi, and one yeast. The mild (physiological) reaction conditions ensured the suppression of undesired side reactions, such as elimination or condensation. Cofactor and inhibitor studies suggest that the racemization proceeds through an equilibrium-controlled enzymatic oxidation-reduction sequence via the corresponding ketones or alpha-diketones, respectively, which were detected in various amounts.

An algorithm for the deconvolution of mass spectroscopic patterns in isotope labeling studies. Evaluation for the hydrogen-deuterium exchange reaction in ketones.

An easy to use computerized algorithm for the determination of the amount of each labeled species differing in the number of incorporated isotope labels based on mass spectroscopic data is described and evaluated. Employing this algorithm, the microwave-assisted synthesis of various alpha-labeled deuterium ketones via hydrogen-deuterium exchange with deuterium oxide was optimized with respect to time, temperature, and degree of labeling. For thermally stable ketones the exchange of alpha-protons was achieved at 180 degrees C within 40-200 min.