THE E-SELECTIN-LIGAND ESL-1 IS LOCATED IN THE GOLGI AS WELL AS ON MICROVILLI ON THE CELL-SURFACE

Neutrophils and subsets of lymphocytes bind to E-selectin, a cytokine inducible adhesion molecule on endothelial cells. The E-selectin-ligan d-1 (ESL-1) is a high affinity glycoprotein ligand which participates in the binding of mouse myeloid cells to E-selectin, The sequence of m ouse ESL-1 is highly homologous to the cysteine rich FGF receptor (CFR ) in chicken and the rat Golgi protein MG160. We have analysed the sub cellular distribution of ESL-1 by indirect immunofluorescence, flow cy tometry, various biochemical techniques and by immunogold scanning ele ctron microscopy, We could localize ESL-1 in the Golgi as well as on t he cell surface of 32Dc13 cells and neutrophils, Cell surface staining was confirmed by cell surface biotinylation and by cell surface immun oprecipitations in which antibodies only had access to surface protein s on intact cells, In addition, ESL-1(high) and ESL-1(low) expressing cells, sorted by flow cytometry, gave rise to high and low immunopreci pitation signals for ESL-1, respectively, Based on immunogold labeling of intact cells, we localized ESL-1 on microvilli of 32Dc13 cells and of the lymphoma cell line K46, Quantitative evaluation determined 80% of the total labeling for ESL-1 on microvilli of K46 cells while 69% of the labeling for the control antigen B220 was found on the planar c ell surface, These data indicate that ESL-1 occurs at sites on the leu kocyte cell surface which are destined for the initiation of cell cont acts to the endothelium.