| 1. |
- Deligny, Audrey, et al.
(författare)
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NDST2 (N-Deacetylase/N-Sulfotransferase-2) Enzyme Regulates Heparan Sulfate Chain Length
- 2016
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 291:36, s. 18600-18607
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of heparan sulfate synthesized by HEK 293 cells overexpressing murine NDST1 and/or NDST2 demonstrated that the amount of heparan sulfate was increased in NDST2-but not in NDST1-overexpressing cells. Altered transcript expression of genes encoding other biosynthetic enzymes or proteoglycan core proteins could not account for the observed changes. However, the role of NDST2 in regulating the amount of heparan sulfate synthesized was confirmed by analyzing heparan sulfate content in tissues isolated from Ndst2(-/-) mice, which contained reduced levels of the polysaccharide. Detailed disaccharide composition analysis showed no major structural difference between heparan sulfate from control and Ndst2(-/-) tissues, with the exception of heparan sulfate from spleen where the relative amount of trisulfated disaccharides was lowered in the absence of NDST2. In vivo transcript expression levels of the heparan sulfate-polymerizing enzymes Ext1 and Ext2 were also largely unaffected by NDST2 levels, pointing to a mode of regulation other than increased gene transcription. Size estimation of heparan sulfate polysaccharide chains indicated that increased chain lengths in NDST2-overexpressing cells alone could explain the increased heparan sulfate content. A model is discussed where NDST2-specific substrate modification stimulates elongation resulting in increased heparan sulfate chain length.
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| 2. |
- Carlsson, Pernilla, et al.
(författare)
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Heparan sulfate biosynthesis: Characterization of an NDST1 splice variant
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Annan publikation (populärvet., debatt m.m.)abstract
- N-Deacetylase/N-sulfotransferases (NDSTs) are Golgi-located enzymes involved in the biosynthesis of heparan sulfate. They are bifunctional enzymes responsible for N-deacetylation of N-acetylglucosamine residues followed by N-sulfation of the generated free amino groups. In this paper we have identified and characterized a splice variant of NDST1 mRNA. The alternatively spliced mRNA transcript was shown to be present in varying amounts in different adult and embryonic mouse tissues. The protein resulting from translation of the spliced transcript (NDST1S) lacks the C-terminal half of fullength NDST and appears to be devoid of enzyme activity. As shown in HEK 293 cells overexpressing NDST1, a high expression of the splice variant resulted in reduced levels of NDST1. Unexpectedly, the level of N-sulfation was largely unaltered in heparan sulfate produced in NDST1S overexpressing cells while 6-O-sulfation was elevated and 2-O-sulfation was reduced. NDST1S shares the ability of NDST1 to interact with EXT2, one of the components of the heparan sulfate copolymerase. We speculate that NDST1S may alter the composition of the tentaive enzyme complex, the GAGosome, resulting in changes in the structure of heparan sulfate synthesized.
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| 3. |
- Dagälv, Anders, et al.
(författare)
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Cell surface mast cell proteoglycans identified as heparin-substituted syndecan-2
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Annan publikation (populärvet., debatt m.m.)abstract
- Connective tissue type mast cells isolated from the peritoneal cavity of mice and then cultured in vitro have been used to answer the question if one cell at a given time point can synthesize heparan sulfate chains with different structure. Characterization of cell surface proteoglycans made by the cells demonstrated that they were identical to syndecan-2, substituted with heparin chains. Ion exchange chromatography showed that the syndecan heparin chains behaved identically as heparin chains recovered from serglycin, inside the cells. This was also the case when mast cells from NDST2 deficient mice were studied. This time, syndecan-2 as well as serglycin derived polysaccharide chains had a lower but identical charge density. We conclude that mast cells only synthesize one kind of heparan sulfate/heparin chain at a time and that polysaccharide chains of identical structure will be found at the cell surface and inside the cell.
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| 4. |
- Dagälv, Anders, et al.
(författare)
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Lack of both lethality and defective in vitro differentiation of embryonic stem cells N-deacetylase/N-sulfotransferase 1 and 2 causes early embryonic
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Annan publikation (populärvet., debatt m.m.)abstract
- NDSTs (N-deacetylase/N-sulfotransferases) are enzymes responsible for N-sulfation during heparan sulfate and heparin biosynthesis. While lack of NDST2 results in defective mast cells and NDST1 deficiency causes neonatal death and lung, skeletal and brain defects, lack of both isoforms is not compatible with embryonic development. We here show that NDST1/2-/- embryos die before E6.5 and that embryos dissected out at E5.5 lack parts of the embryo/extraembryonic tissue. Consistent with their in vivo behavior, in vitro cultured NDST1/2 deficient embryos displayed impaired ability of inner cell mass proliferation. In addition, markers for all the three germ layers had a disturbed expression pattern in isolated NDST1/2 deficient embryonic stem (ES) cells. Characterization of heparan sulfate (HS) structure in control ES cells and in ES cells lacking NDST1, NDST2 or both NDST1 and NDST2 revealed big differences. As expected, control cells synthesized HS with the highest degree of sulfation closely followed by HS from NDST2-/- cells, which in turn was more sulfated than HS produced by NDST1-/- cells. HS from NDST1/2-/- cells was almost devoid of sulfate groups. Notably, lack of one NDST isoform did not result in increased expression of any of the others. While all cell types except the NDST1/2-/- cells produced HS with a higher degree of sulfation when allowed to differentiate for 8 days, HS from control cells was still more heavily sulfated than that produced by NDST2-/- cells followed by the HS of NDST1-/- cells. The increase in sulfation was paralleled by increased expression of NDST transcripts and could also be recorded as increased N-sulfotransferase activity of cell lysates. While NDST1/2 deficient ES cells were unable to differentiate into beating cardiomyocytes all NDST1-/- and control embryoid bodies had started to beat after 4 days of culture. Surprisingly, NDST2 deficiency resulted in delayed cardiomyocyte differentiation.
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| 5. |
- Dagälv, Anders, et al.
(författare)
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Lowered Expression of Heparan Sulfate/Heparin Biosynthesis Enzyme N-Deacetylase/N-Sulfotransferase 1 Results in Increased Sulfation of Mast Cell Heparin
- 2011
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 286:52, s. 44433-44440
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Tidskriftsartikel (refereegranskat)abstract
- Deficiency of the heparan sulfate biosynthesis enzyme N-deacetylase/N-sulfotransferase 1 (NDST1) in mice causes severely disturbed heparan sulfate biosynthesis in all organs, whereas lack of NDST2 only affects heparin biosynthesis in mast cells (MCs). To investigate the individual and combined roles of NDST1 and NDST2 during MC development, in vitro differentiated MCs derived from mouse embryos and embryonic stem cells, respectively, have been studied. Whereas MC development will not occur in the absence of both NDST1 and NDST2, lack of NDST2 alone results in the generation of defective MCs. Surprisingly, the relative amount of heparin produced in NDST1(+/-) and NDST1(-/-) MCs is higher (approximate to 30%) than in control MCs where approximate to 95% of the (35)S-labeled glycosaminoglycans produced is chondroitin sulfate. Lowered expression of NDST1 also results in a higher sulfate content of the heparin synthesized and is accompanied by increased levels of stored MC proteases. A model of the GAGosome, a hypothetical Golgi enzyme complex, is used to explain the results.
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| 6. |
- Dagälv, Anders
(författare)
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Role of Heparan Sulfate N-sulfation in Mouse Embryonic Development
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heparan sulfate (HS) is a sulfated glycosaminoglycan expressed by all cells in the body. It is found at the cell surface and in the extracellular matrix where it binds a large amount of various ligands including growth factors and morphogens. HS is important for building up morphogen gradients during embryonic development and to act as coreceptors for signaling molecules. Many different Golgi enzymes are involved in the biosynthesis of HS. It is known that some of these enzymes interact with each other but not how the whole biosynthesis machinery works or how the cell regulates the structure of the HS that it produces. In this thesis, cells and mice deficient in two of these biosynthetic enzymes, glucosaminyl N-deacetylase/N-sulfotransferase-1 (NDST1) and the isoform NDST2 have been studied. NDSTs perform the first modifications during biosynthesis where they replace N-acetyl groups on N-acetyl-glucosamine units with sulfate groups. It is known that deficiency of NDST1 is lethal, while lack of NDST2 only results in abnormal connective tissue type mast cells. Here it is shown that deficiency of both NDST1 and NDST2 is embryonically lethal. The embryonic stem (ES) cells extracted from the inner cell mass of double knockout blastocysts show in addition an impaired differentiation capacity compared to wild-type ES cells and fail completely to differentiate into cardiac muscle cells which NDST1-/-, NDST2-/- and wild-type ES cells all do. Cultured mast cells that lack NDST2 produce heparin that is low-sulfated compared to wild-type HS. To our surprise, we could show that mast cells deficient in NDST1 instead produce a more highly sulfated heparin than wild-type cells. We use a model that predicts that the biosynthesis enzymes work together in a multienzyme complex, the GAGosome, to explain our results. We hypothesize that NDST1 has a higher affinity for the GAGosome than NDST2 which only in the absence of NDST1 gets incorporated into the enzyme complex. When all GAGosomes contain NDST2, a more highly sulfated glycosaminoglycan chain will be synthesized. A splice variant of NDST1, NDST1S, has also been studied. We could show that NDST1S lacks enzyme activity but that it probably has the capacity to incorporate into GAGosomes. Overexpression of NDST1S results in altered structure of the HS produced by the cells. We speculate that expression of the splice variant during development may be one way to regulate HS structure.
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| 7. |
- Forsberg, Maud, et al.
(författare)
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Undersulfation of Heparan Sulfate Restricts Differentiation Potential of Mouse Embryonic Stem Cells
- 2012
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 287:14, s. 10853-10862
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Tidskriftsartikel (refereegranskat)abstract
- Heparan sulfate proteoglycans, present on cell surfaces and in the extracellular matrix, interact with growth factors and morphogens to influence growth and differentiation of cells. The sulfation pattern of the heparan sulfate chains formed during biosynthesis in the Golgi compartment will determine the interaction potential of the proteoglycan. The glucosaminyl N-deacetylase/N-sulfotransferase (NDST) enzymes have a key role during biosynthesis, greatly influencing total sulfation of the heparan sulfate chains. The differentiation potential of mouse embryonic stem cells lacking both NDST1 and NDST2 was studied using in vitro differentiation protocols, expression of differentiation markers, and assessment of the ability of the cells to respond to growth factors. The results show that NDST1 and NDST2 are dispensable for mesodermal differentiation into osteoblasts but necessary for induction of adipocytes and neural cells. Gene expression analysis suggested a differentiation block at the primitive ectoderm stage. Also, GATA4, a primitive endoderm marker, was expressed by these cells. The addition of FGF4 or FGF2 together with heparin rescued the differentiation potential to neural progenitors and further to mature neurons and glia. Our results suggest that the embryonic stem cells lacking both NDST1 and NDST2, expressing a very low sulfated heparan sulfate, can take the initial step toward differentiation into all three germ layers. Except for their potential for mesodermal differentiation into osteoblasts, the cells are then arrested in a primitive ectoderm and/or endoderm stage.
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| 8. |
- Holley, Rebecca J., et al.
(författare)
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Mucopolysaccharidosis Type I, Unique Structure of Accumulated Heparan Sulfate and Increased N-Sulfotransferase Activity in Mice Lacking alpha-L-iduronidase
- 2011
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 286:43, s. 37515-37524
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Tidskriftsartikel (refereegranskat)abstract
- Mucopolysaccharide (MPS) diseases are characterized by accumulation of glycosaminoglycans (GAGs) due to deficiencies in lysosomal enzymes responsible for GAG breakdown. Using a murine model of MPSI Hurler (MPSIH), we have quantified the heparan sulfate (HS) accumulation resulting from alpha-L-iduronidase (Idua) deficiency. HS levels were significantly increased in liver and brain tissue from 12-week-old Idua(-/-) mice by 87- and 20-fold, respectively. In addition, HS chains were shown to contain significantly increased N-, 2-O-, and 6-O-sulfation. Disaccharide compositional analyses also uncovered an HS disaccharide uniquely enriched in MPSIH, representing the terminal iduronic acid residue capping the non-reducing end of the HS chain, where no further degradation can occur in the absence of Idua. Critically, we identified that excess HS, some of which is colocalized to the Golgi secretory pathway, acts as a positive regulator of HS-sulfation, increasing the N-sulfotransferase activity of HS-modifying N-deacetylase/N-sulfotransferase enzymes. This mechanism may have severe implications during disease progression but, now identified, could help direct improved therapeutic strategies.
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| 9. |
- Holmborn, Katarina, et al.
(författare)
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Divergent effects of heparan sulfate/heparin biosynthesis enzymes N-deacetylase/N-sulfotransferase 1 and 2 on Mast cell development
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Deficiency of the heparan sulfate (HS) biosynthesis enzyme N-deacetylase/N-sulfotransferase 1 (NDST1) in mice causes severely disturbed HS biosynthesis in all organs, while lack of NDST2 only affects heparin biosynthesis in mast cells (MCs). To investigate the individual and combined roles of NDST1 and NDST2 during MC development, cultured terminally differentiated MCs from adult mice, in vitro differentiated MCs derived from mouse embryos and embryonic stem cells, respectively, have been studied. While MC development will not occur in the absence of both NDST1 and NDST2, lack of NDST2 alone results in the generation of defective MCs. Surprisingly, NDST1 deficiency results in the formation of MCs which compared to wild type MCs contain increased levels of proteases specific for the connective tissue type MCs as well as increased amounts and degree of sulfation of heparin. A model of the GAGosome, a tentative Golgi enzyme complex, is used to explain the results.
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| 10. |
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