Mitotic separation of daughter cells in the human lymphoma B cell line Daudi involves L-selectin engagement and shedding.
OBJECTIVE
A novel role for shedding of the surface molecule L-selectin has been proposed as an adjunctive phenomenon during cell detachment from marrow stroma or vessel endothelium. We wished to examine whether variations in expression of L-selectin on a lymphoma B cell line were linked to shedding.


METHODS
Mapping of L-selectin expression on the surface of Daudi lymphoma cells was performed by flow cytometry, fluorescence microscopy, and electron microscopy. Levels of shed L-selectin were evaluated by Western blotting of culture supernatants. Evaluation of cell cycle and proliferative activity was performed by flow cytometry.


RESULTS
Large Daudi cells in S+G(2)/M phases were L-selectin positive, whereas small Daudi cells in G(0)/G(1) phase were L-selectin negative. During mitosis, L-selectin was distributed along the cleavage furrow, and gradually lost. Electron microscopy revealed that separating Daudi cells were negative for L-selectin on the entire surface, except minute aggregates of L-selectin within the cleavage furrow. Addition of agents known to interfere with the ligand-binding portion of L-selectin (sulfatides, MoAbs: Lam1.3 and TQ1) results in loss of L-selectin. Removal of L-selectin by digestion with chymotrypsin inhibits Daudi proliferation. The MoAb FMC46 did not interfere with proliferation. Proliferating Daudi cells produced large quantities of shed L-selectin. Inhibition of Daudi proliferation resulted in levels of shed L-selectin below the limit of detection.


CONCLUSIONS
L-selectin is re-distributed on the cell surface of Daudi cells during the last phase of mitosis, in which plasma membrane invagination occurs between newly formed daughter cells. Shedding of L-selectin is involved in the cytokinesis of Daudi cells.
Po
J L
JL
Dept. Surgery, Royal Victoria Hospital, Montreal, PQ, Canada.
Mak
A
A
Ginsberg
D
D
Huerta
P
P
Manoukian
R
R
Shustik
C
C
Jensen
G S
GS
D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000473:pathology*; D002453:Cell Cycle; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D019041:L-Selectin / Q000502:physiology*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008938:Mitosis; D009363:Neoplasm Proteins / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000166:cytology
D009363:Neoplasm Proteins; D019041:L-Selectin