Cell Surface Sialylation and Ecto-sialyltransferase Activity of Human CD34 Progenitors from Peripheral Blood and Bone Marrow.

Surface expressed negatively charged sialoglycans contribute to the regulation of adhesive cellular Interactions and are thus Involved In the growth and dlfferentlaton of hematopoietic progenitor cells. In particular, the cell surface sialylatlon state may govern the liberation of CD34+ hematopoietic precursors from bone marrow stroma cells and extracellular matrbc. in order to assess the overall surface sialylatlon of live human 0034 hematopoietic precursor cells, we applied a previously described flow cytometric enzyme assay. Cells with and without slalidase pretreatmem were incubated in the presence of fluorescent CUP-siallc add and exogenous STSGall. Thus sialylatlon of surface-expressed bctosamlne residues was analysed. We demonstrated that surface lactosamlnes of CD34 precursors derived from bone marrow and peripheral blood are over 55% sialylated, predominantly in ai,B linkage. These results are In accordance with flow cytometric analysis of surface lectin staining. Sialic ackt specific lectins UAA and SNA were strongly bound whereas SBA, WA, and PNA became reactiva only after sialklase pretreatment. CD344 leukemia cell lines TF1 and KGIa also showed a high degree of surface sialylation whereas cell line KG1 expressed to the largest extent free lactosamlnes. In these cell lines, aifi and a sialylated residues were present In equal amounts, in a variation of the flow cytometric enzyme assay, live cells were incubated without exogenous STGa I to measure the activity of endogenous ecto-sialyltransferase. Ecto sialyltransferase activity was observed in all CD34+ cells which was able to resialylate major surface glycoproteins such as HLA Class I, CD45, CD43, and CD34. The ecto-sialyltransferase may serve to maintain or Increase surface sialylation rapidly without de novo synthesis.

SCHWARTZ-ALBIEZ R.;  MERLING A.;  MARTIN Simona;  HAAS R.;  GROSS H.J.; 

2005-07-29

SPRINGER

JRC30041

https://publications.jrc.ec.europa.eu/repository/handle/JRC30041,