A5062772273- Diabetes, Cardiovascular Risks, and Lipoproteins
- Lipid metabolism and disorders
- Lipoproteins and Cardiovascular Health
- Cancer, Lipids, and Metabolism
- Enzyme Catalysis and Immobilization
- Lipid metabolism and biosynthesis
- Diabetes and associated disorders
- Cholesterol and Lipid Metabolism
- Caveolin-1 and cellular processes
- Analytical Chemistry and Chromatography
- Glycosylation and Glycoproteins Research
- Proteoglycans and glycosaminoglycans research
- PARP inhibition in cancer therapy
- Cancer, Hypoxia, and Metabolism
- Pancreatic function and diabetes
- Signaling Pathways in Disease
- Carbohydrate Chemistry and Synthesis
- Lipid Membrane Structure and Behavior
- Protein Interaction Studies and Fluorescence Analysis
- Adipose Tissue and Metabolism
- Microbial Metabolic Engineering and Bioproduction
- Blood properties and coagulation
- Metabolism, Diabetes, and Cancer
- Peroxisome Proliferator-Activated Receptors
- Viral gastroenteritis research and epidemiology
Tallinn University of Technology
2014-2025
Umeå University
2002-2014
Tallinn University
2014
Max Perutz Labs
2008
University College London
2008
National Institute of Chemical Physics and Biophysics
1998-2003
Novo Nordisk (Denmark)
1996
Aarhus University
1993-1994
Eppendorf (Germany)
1994
Estonian Academy of Sciences
1993
Lipoprotein lipase (LPL) has a central role in lipoprotein metabolism to maintain normal levels blood and, through tissue specific regulation of its activity, determine when and what tissues triglycerides are unloaded. Recent data indicate that angiopoietin-like protein (Angptl)-4 inhibits LPL retards catabolism. We demonstrate here the N-terminal coiled-coil domain Angptl-4 binds transiently interaction results conversion enzyme from catalytically active dimers inactive, but still folded,...
Lipoprotein lipase (LPL) causes a marked increase in the cellular binding of beta-migrating very low density lipoprotein (beta-VLDL) to large receptor compatible with alpha 2-macroglobulin (alpha 2MR)/low receptor-related protein (LRP) (Beisiegel, U., Weber, W., and Bengtsson-Olivecrona, G. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 8342-8346). Here we demonstrate that LPL binds alpha-chain purified 2MR/LRP immobilized on microtiter plates. The binding, apparently multiple sites, was blocked...
Apolipoproteins (apo) C-I and C-III are known to inhibit lipoprotein lipase (LPL) activity, but the molecular mechanisms for this remain obscure. We present evidence that either apoC-I or apoC-III, when bound triglyceride-rich lipoproteins, prevent binding of LPL lipid/water interface. This results in decreased lipolytic activity enzyme. Site-directed mutagenesis revealed hydrophobic amino acid residues centrally located apoC-III molecule critical attachment lipid emulsion particles...
The low density lipoprotein receptor-related protein (LRP) is a multifunctional endocytic cell-surface receptor that binds and internalizes diverse array of ligands. contains four putative ligand-binding domains, generally referred to as clusters I, II, III, IV. In this study, soluble recombinant fragments, representing each the individual clusters, were used map binding sites set structurally functionally distinct Using surface plasmon resonance, we studied these fragments...
Transgenic and gene disruption experiments in mice have revealed that apolipoprotein (apo) A-V is a potent regulator of plasma triglyceride (TG) levels. To investigate the molecular basis apoA-V function, ability isolated recombinant to modulate lipoprotein lipase (LPL) activity was examined vitro. With three distinct lipid substrate particles, including very low-density (VLDL), TG/phospholipid emulsion, or dimyristoylphosphatidylcholine liposomes, had little effect on LPL activity. In...
The interaction of lipoprotein lipase (LPL) with heparan sulfate and size-fractionated fragments heparin was characterized by several approaches (stabilization, sedimentation, surface plasmon resonance, circular dichroism, fluorescence). results show that decasaccharides form a 1:1 complex dimeric LPL are the shortest which can completely satisfy binding regions in LPL. Equimolar concentrations octasaccharides also stabilized LPL, while shorter (hexa- tetrasaccharides) were less efficient....
Apolipoprotein A-V is a potent modulator of plasma triacylglycerol levels. To investigate the molecular basis for this phenomenon we explored ability apolipoprotein A-V, in most experiments complexed to disks dimyristoylphosphatidylcholine, interact with two members low density lipoprotein receptor family, receptor-related protein and mosaic type-1 receptor, SorLA. Experiments using surface plasmon resonance showed specific binding both free lipid-bound receptors. The was calcium dependent...
Lipoprotein lipase (LPL) was rapidly inactivated by low concentrations of the active‐site inhibitor tetrahydrolipstatin (THL). The presence amphiphils (e.g. long‐chain fatty acids) or lipid/water interfaces (lipid emulsions) required for inhibition to occur. Apolipoprotein CII increased maximal inactivation rate constant 1.8‐fold in an emulsion triacylglycerols, but had no effect tributyrylglycerol. fully inhibited enzyme a ratio THL/LPL nearly 2, indicating that both subunits LPL homo‐dimer...
It has previously been shown that lipoprotein lipase can mediate uptake of remnant particles via binding to the low density receptor-related proteinla,-macroglobulin receptor (LRP).Binding lipase, and triglyceride-rich lipoproteins associated with LRP depends on an intact carboxyl-terminal folding domain (Nykjaer,
The purpose of this study was to identify rare APOA5 variants in 130 severe hypertriglyceridemic patients by sequencing, and test their functionality, since no patient recall possible.We studied the impact vitro on LPL activity receptor binding 3 novel heterozygous variants, apoAV-E255G, -G271C, -H321L, together with previously reported -G185C, -Q139X, -Q148X, a construct -Delta139 147. Using VLDL as TG-source, compared wild type, apoAV-G255, -L321 -C185 showed reduced activation (-25%...
Interaction of different classes lipoproteins with heparan sulfate, heparin, and lipoprotein lipase was studied by a surface plasmon resonance based technique on BIAcore. The proteoglycans were covalently attached to sensor chips as previously described [Lookene, A., Chevreuil, O., Ostergaard, P., & Olivecrona, G. (1996) Biochemistry 35, 12155-12163]. Binding all lipoproteins, except for beta-VLDL, endothelial sulfate low. chylomicrons (from rat lymph) human VLDL much increased the presence...
Previous studies had pointed to an important function of a putative exposed loop in the C-terminal domain lipoprotein lipase for activity against emulsified lipid substrates. This contains 3 tryptophan residues (Trp390, Trp393, and Trp394). We have expressed characterized mutants with alanine substitutions at positions 55, 114, 382, 390, 393, 394 double mutant 393 394. The N-terminal (W55A W114A) led poor expression completely inactive variants. Heparin-Sepharose chromatography showed that...
Lipoprotein lipase (LPL), a key enzyme in the metabolism of triglyceride-rich plasma lipoproteins, is homodimer. Dissociation to monomers leads loss activity. Evidence that LPL dimers rapidly exchange subunits was demonstrated by fluorescence resonance energy transfer between labeled with Oregon Green and tetrametylrhodamine, respectively, also formation heterodimers composed radiolabeled biotinylated captured on streptavidine-agarose. Compartmental modeling inactivation kinetics confirmed...
The active form of lipoprotein lipase (LPL) is a noncovalent homodimer 55-kDa subunits. dimer unstable and tends to undergo irreversible dissociation into inactive monomers. We noted that preparation such monomers slowly regained traces activity under assay conditions with substrate, heparin, serum or in cell culture medium containing serum. therefore studied the refolding pathway LPL after full denaturation 6 M guanidinium chloride 1 chloride. In crude systems, we identified as factor...
Lipoprotein lipase (LPL) is a non-covalent, homodimeric, N-glycosylated enzyme important for metabolism of blood lipids. LPL regulated by yet unknown post-translational events affecting the levels active dimers. On co-expression with human molecular chaperones, we found that calreticulin had most pronounced effects on activity, but calnexin was also effective. Calreticulin caused 9-fold increase in LPL, amounting to about 50% expressed protein. The total expression protein increased less...
During the diagnosis of three unrelated patients with severe hypertriglyceridemia, APOA5 mutations [p.(Ser232_Leu235)del, p.Leu253Pro, and p.Asp332ValfsX4] were found without evidence concomitant LPL, APOC2, or GPIHBP1 mutations. The molecular mechanisms by which result in hypertriglyceridemia remain poorly understood, functional impairment/s induced these specific was not obvious. Therefore, we performed a thorough structural analysis that included follow-up their closest relatives,...
LPL hydrolyzes triglycerides in plasma lipoproteins. Due to the complex regulation mechanism, it has been difficult mimic physiological conditions under which acts vitro. We demonstrate that isothermal titration calorimetry (ITC), using human as substrate, overcomes several limitations of previously used techniques. The high sensitivity ITC allows continuous recording heat released during hydrolysis. Both initial rates and kinetics for complete hydrolysis lipids can be studied. rate was...
Lipoprotein lipase has been found to efficiently mediate binding of lipoproteins cell surfaces and the low density lipoprotein (LDL) receptor-related protein (LRP) under culture conditions (Beisiegel et al. 1991. Proc. Natl. Acad. Sci. USA. 88: 8242-8346). This supports previously proposed idea that could have a role in receptor-mediated uptake chylomicron remnants liver. We investigated effects on clearance chylomicrons during perfusions rat livers. The were doubly labeled vivo with...
Treatment of bovine lipoprotein lipase (LPL) with chymotrypsin results in cleavage between residues Phe390‐Ser391 and Trp392‐Ser393, indicating that this region is exposed the native conformation LPL. Two main fragments are generated, one large including aminoterminus (chymotrypsin‐truncated LPL = c‐LPL) small, carboxy‐terminal fragment. The small fragment not stable, but further degraded by protease. Isolated c‐LPL has full catalytic activity against tributyryl glycerol (tributyrin) p...
Lipoprotein lipase (LPL), a crucial enzyme in the intravascular hydrolysis of triglyceride-rich lipoproteins, is potential drug target for treatment hypertriglyceridemia. The activity and stability LPL are influenced by complex ligand network. Previous studies performed dilute solutions suggest that can appear various oligomeric states. However, it was not known how physiological environment, blood plasma, affects action LPL. In current study, we demonstrate albumin, major protein component...