Dimeric galectin-1 induces surface exposure of phosphatidylserine and phagocytic recognition of leukocytes without inducing apoptosis.
We report that human galectin-1 (dGal-1), a small dimeric beta-galactoside-binding protein, induces phosphatidylserine (PS) exposure, measured by Annexin V staining, on human promyelocytic HL-60 cells, T leukemic MOLT-4 cells, and fMet-Leu-Phe-activated, but not resting, human neutrophils. This effect of dGal-1 on HL-60 and MOLT-4 cells is enhanced by pretreatment of the cells with neuraminidase, but treatment of resting neutrophils with neuraminidase does not enhance their sensitivity to dGal-1. Although the induction of staining with Annexin V is often associated with apoptosis, the dGal-1-treated HL-60 cells, MOLT-4 cells, and activated neutrophils do not undergo apoptosis, and there is no detectable DNA fragmentation. HL-60 and MOLT-4 cells treated with dGal-1 continue to grow normally. By contrast, camptothecin-treated HL-60 cells, etoposide-treated MOLT-4 cells, and anti-Fas-treated neutrophils exhibit extensive DNA fragmentation and/or cell death. Lactose inhibits the dGal-1-induced effects, indicating that dGal-1-induced signaling requires binding to cell surface beta-galactosides. The dimeric form of Gal-1 is required for signaling, because a monomeric mutant form of Gal-1, termed mGal-1, binds to cells but does not cause these effects. Importantly, dGal-1, but not mGal-1, treatment of HL-60 cells and activated human neutrophils significantly promotes their phagocytosis by activated mouse macrophages. These dGal-1-induced effects are distinguishable from apoptosis, but like apoptotic agents, prepare cells for phagocytic removal. Such effects of dGal-1 may contribute to leukocyte homeostasis.
Dias-Baruffi
Marcelo
M
Department of Biochemistry and Molecular Biology and Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Zhu
Hui
H
Cho
Moonjae
M
Karmakar
Sougata
S
McEver
Rodger P
RP
Cummings
Richard D
RD
D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D016923:Cell Death; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D019281:Dimerization; D005434:Flow Cytometry; D037483:Galectin 1 / Q000737:chemistry / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D009154:Mutation; D009439:Neuraminidase / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D010587:Phagocytosis; D010718:Phosphatidylserines / Q000378:metabolism*; D011485:Protein Binding; D012542:Scattering, Radiation; D015398:Signal Transduction; D013997:Time Factors
D037483:Galectin 1; D010718:Phosphatidylserines; D009439:Neuraminidase