| 1. |
- Carlsson, Michael, et al.
(författare)
-
Galectin-1-binding glycoforms of haptoglobin with altered intracellular trafficking, and increase in metastatic breast cancer patients.
- 2011
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:10
-
Tidskriftsartikel (refereegranskat)abstract
- Sera from 25 metastatic breast cancer patients and 25 healthy controls were subjected to affinity chromatography using immobilized galectin-1. Serum from the healthy subjects contained on average 1.2 mg per ml (range 0.7-2.2) galectin-1 binding glycoproteins, whereas serum from the breast cancer patients contained on average 2.2 mg/ml (range 0.8-3.9), with a higher average for large primary tumours. The major bound glycoproteins were α-2-macroglobulin, IgM and haptoglobin. Both the IgM and haptoglobin concentrations were similar in cancer compared to control sera, but the percentage bound to galectin-1 was lower for IgM and higher for haptoglobin: about 50% (range 20-80) in cancer sera and about 30% (range 25-50) in healthy sera. Galectin-1 binding and non-binding fractions were separated by affinity chromatography from pooled haptoglobin from healthy sera. The N-glycans of each fraction were analyzed by mass spectrometry, and the structural differences and galectin-1 mutants were used to identify possible galectin-1 binding sites. Galectin-1 binding and non-binding fractions were also analyzed regarding their haptoglobin function. Both were similar in forming complex with haemoglobin and mediate its uptake into alternatively activated macrophages. However, after uptake there was a dramatic difference in intracellular targeting, with the galectin-1 non-binding fraction going to a LAMP-2 positive compartment (lysosomes), while the galectin-1 binding fraction went to larger galectin-1 positive granules. In conclusion, galectin-1 detects a new type of functional biomarker for cancer: a specific type of glycoform of haptoglobin, and possibly other serum glycoproteins, with a different function after uptake into tissue cells.
|
|
| 2. |
- Lepur, Adriana
(författare)
-
Functional properties of galectin-3. Beyond the sugar binding.
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Contemporary diseases like diabetes, asthma, atherosclerosis etc. are marked by chronic inflammation, often supported by the activity of different macrophages. Proteins from galectin family were found to contribute to disease pathophysiology. Therefore, there is an intensive interest in understanding different galectin functions. The aim of this thesis was to pin-point specific galectin-3 roles in differently activated macrophages. Additional aim was to understand the mechanism and consequences of galectin-3 ligand binding. In the first paper galectin-3 endocytosis was studied in a system of differently activated macrophages. We found that inflammatory, M1, and alternatively activated, M2, macrophages have a large capacity to internalize externally added galectin-3, besides expressing and secreting galectin-3. Additionally, we found that galectin-3 does not require the functional carbohydrate recognition domain (CRD) for its endocytosis. In the second paper we used M2 macrophages to study how galectin-1 directs the endocytosis of hemoglobin-haptoglobin complex. Our results indicated that galectin-1 bound fraction of the complex takes a recycling intracellular route instead of the pathway for degradation. The third paper shows how certain complex carbohydrate ligands can induce galectin-3 self-association that involves CRD to CRD binding. This “type-C” self-association engages more galectin-3 molecules than there are available glycan ligands and can explain certain biological events that require fast galectin-3 mobilization. In the fourth paper we tested the inhibitory potential of a few plant products for several galectins. We found that their activity was very weak, hence the search for more potent anti-galectin, perhaps also anti-inflammatory remedies continues.
|
|
| 3. |
- Lepur, Adriana, et al.
(författare)
-
Galectin-3 endocytosis by carbohydrate independent and dependent pathways in different macrophage like cell types.
- 2012
-
Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 0304-4165. ; 1820:7, s. 804-818
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Galectin-3 (the Mac-2 antigen) is abundantly expressed in both macrophage like cells and certain non-macrophage cells. We have studied endocytosis of galectin-3 as one important step relevant for its function, and compared it between variants of a macrophage like cell line, and non-macrophage cells. METHODS: Endocytosis of galectin-3 was observed by fluorescence microscopy and measured by flow cytometry. The endocytosis mechanism was analysed using galectin-3 mutants, galectin-3 inhibitors and endocytic pathways inhibitors in the human leukaemia THP-1 cell line differentiated into naïve (M0), classical (M1) or alternatively activated (M2) macrophage like cells, and the non-macrophage cell lines HFL-1 fibroblasts and SKBR3 breast carcinoma. RESULTS: Galectin-3 endocytosis in non-macrophage cells and M2 cells was blocked by lactose and a potent galectin-3 inhibitor TD139, and also by the R186S mutation in the galectin-3 carbohydrate recognition domain (CRD). In M1 cells galectin-3 endocytosis could be inhibited only by chlorpromazine and by interference with the non-CRD N-terminal part of galectin-3. In all the cell types galectin-3 entered early endosomes within 5-10min, to be subsequently targeted mainly to non-degradative vesicles, where it remained even after 24h. CONCLUSIONS: Galectin-3 endocytosis in M1 cells is receptor mediated and carbohydrate independent, while in M2 cells it is CRD mediated, although the non-CRD galectin-3 domain is also involved. General significance The demonstration that galectin-3 endocytosis in M1 macrophages is carbohydrate independent and different from M2 macrophages and non-macrophage cells, suggests novel, immunologically significant interactions between phagocytic cells, galectin-3 and its ligands.
|
|
| 4. |
- Lepur, Adriana, et al.
(författare)
-
Ligand induced galectin-3 self-association.
- 2012
-
Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 287:26, s. 21751-21756
-
Tidskriftsartikel (refereegranskat)abstract
- Many functions of galectin-3 entail binding of its carbohydrate recognition site to glycans of a glycoprotein, resulting in cross-linking thought to be mediated by its N-terminal non-carbohydrate-binding domain. Here we studied interaction of galectin-3 with the model glycoprotein asialofetuin (ASF), using a fluorescence anisotropy (FA) assay to measure the concentration of free galectin carbohydrate recognition sites in solution. Surprisingly, in the presence of ASF this remained low even at high galectin-3 concentrations, showing that many more galectin-3 molecules were engaged than expected due to the about 9 known glycan based binding sites per ASF molecule. This suggests that, after ASF induced nucleation, galectin-3 associates with itself by the carbohydrate recognition site binding to another galectin-3 molecule, possibly forming oligomers. We named this type-C self-association to distinguish it from the previously proposed models (type-N) where galectin-3 molecules bind to each other through the N-terminal domain, and all carbohydrate recognition sites are available for binding glycans. Both types of self-association can result in precipitates, as measured here by turbidometry and dynamic light scattering. Type-C self-association and precipitation occurred even with a galectin-3 mutant (R186S) that bound poorly to ASF, but required much higher concentration (~50μM) compared to wild type (~1μM). ASF also induced weaker type-C self-association of galectin-3 lacking its N-terminal part, but, as expected, no precipitation. Neither a monovalent or divalent LacNAc containing glycan induced type-C self-association, even if the latter gave precipitates with high concentrations of galectin-3 (> ~50μM) in agreement with published results, and perhaps due to type-N self-association.
|
|
| 5. |
- Stegmayr, John, et al.
(författare)
-
Low or No Inhibitory Potency of the Canonical Galectin Carbohydrate-binding Site by Pectins and Galactomannans
- 2016
-
Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 291:25, s. 13318-13334
-
Tidskriftsartikel (refereegranskat)abstract
- Some complex plant-derived polysaccharides, such as modified citrus pectins and galactomannans, have been shown to have promising anti-inflammatory and anti-cancer effects. Most reports propose or claim that these effects are due to interaction of the polysaccharides with galectins because the polysaccharides contain galactose-containing side chains that might bind this class of lectin. However, their direct binding to and/or inhibition of the evolutionarily conserved galactoside-binding site of galectins has not been demonstrated. Using a well established fluorescence anisotropy assay, we tested the direct interaction of several such polysaccharides with physiological concentrations of a panel of galectins. The bioactive pectic samples tested were very poor inhibitors of the canonical galactoside-binding site for the tested galectins, with IC50 values >10 mg/ml for a few or in most cases no inhibitory activity at all. The galactomannan Davanat® was more active, albeit not a strong inhibitor (IC50 values ranging from 3 to 20 mg/ml depending on the galectin). Pure synthetic oligosaccharide fragments found in the side chains and backbone of pectins and galactomannans were additionally tested. The most commonly found galactan configuration in pectins had no inhibition of the galectins tested. Galactosylated tri- and pentamannosides, representing the structure of Davanat®, had an inhibitory effect of galectins comparable with that of free galactose. Further evaluation using cell-based assays, indirectly linked to galectin-3 inhibition, showed no inhibition of galectin-3 by the polysaccharides. These data suggest that the physiological effects of these plant polysaccharides are not due to inhibition of the canonical galectin carbohydrate-binding site.
|
|
