Scanning electron microscopy study of neutrophil membrane tubulovesicular extensions (cytonemes) and their role in anchoring, aggregation and phagocytosis. The effect of nitric oxide |
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Authors: | Galkina Svetlana I Molotkovsky Julian G Ullrich Volker Sud'ina Galina F |
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Affiliation: | A. N. Belozersky Institute of Physico-Chemical Biology of the M. V. Lomonosov Moscow State University, 119992, Moscow, Leninskie gory, Building A, Moscow, Russia. galkina@genebee.msu.ru |
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Abstract: | We have shown that human neutrophils develop dynamic thin and very long tubulovesicular extensions (cytonemes) upon adhesion to fibronectin, if cell spreading was blocked by Na(+)-free medium or by 4-bromophenacyl bromide, N-ethylmaleimide, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole and cytochalasin D (S. I. Galkina, G. F. Sud'ina and V. Ullrich, (2001). Exp. Cell Res. 266, 222-228). In the present work we found that similar in size and behavior tubulovesicular extensions were formed on the neutrophil cell bodies upon adhesion to fibronectin-coated substrata in the presence of the nitric oxide donor diethylamine NONOate. In the presence of the nitric oxide synthase inhibitor N-omega-nitro-L-arginine methyl ester, neutrophils were well spread and had no microextensions. Using scanning electron microscopy, we demonstrated that tubulovesicular extensions of neutrophils executed long-range adhesion and binding objects for phagocytosis, such as serum-opsonized zymosan particles and erythrocytes. Tubulovesicular extensions anchored neutrophils to substrata in a beta1 and beta2 integrin-independent, but L-selectin-dependent manner. BODIPY-sphingomyelin impaired development of tubulovesicular extension, and heparitinase 1 played a role in their destruction. Membrane tubulovesicular extensions are supposed to represent protrusions of an intracellular exocytotic traffic and serve as cellular sensory and adhesive organelles. Nitric oxide seems to play a role in regulation of tubulovesicular extensions formation, thus affecting neutrophil adhesive interactions and phagocytosis. |
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Keywords: | Neutrophil (polymorphonuclear leukocyte) Membrane tubulovesicular extensions Cytonemes Adhesion Spreading Phagocytosis β 1 and β 2 integrin l-selectin Heparitinase Nitric oxide Golgi complex |
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