ИСТИНА

Our scanning electron microscopy study revealed that neutrophils can develop dynamic thread-like membrane tubulovesicular extensions (cytonemes) upon adhesion to fibronectin-coated substrata in the presence of: (i) agents disrupting actin cytoskeleton; (ii) inhibitor of GTPase dynamin; (iii) nitric oxide (NO) donor; (iv) inhibitors of vacuolar-type ATPase or glucose metabolism. Cytonemes have a uniform diameter along their entire length and consist of membrane vesicles and tubules that are aligned in a row. The diameter of a cytoneme varies from 150 to 250 nm depending on conditions. Cytonemes can reach several cell diameters in length and are also characterized by a rapid rate of growth (1–5 µm/min), a high degree of flexibility and mobility, and a capacity for shedding from the cell surface. Cytonemes attach neutrophils to fibronectin, establish long-range cell-cell contacts and bind bacteria over a distance. Proteome analysis indicated that cytonemes contain bactericides typical for neutrophil secretory granules along with cytoplasmic proteins, such as glycolytic enzymes and actin cytoskeleton components. NO appears to be a physiological inductor of cytoneme formation in neutrophils. In the presence of NO neutrophil interactions with bacteria shifted from phagocytosis to extracellular binding by cytonemes. Killing of bacteria in this case occurs due to release of bactericides from cytonemes. We assume that cytonemes represent protrusions of constitutive secretory pathway of neutrophils. Normally constitutive secretion occurs as membrane vesicle scission from the plasma membrane. Agents capable of initiating the cytoneme formation impair exocytotic vesicle scission from the plasma membrane and from each other. As a result secretory process extends from the cells as cytonemes. The capacity to long-range communications via cytonemes is a common property of prokaryotes and eukaryotes. We demonstrated that Gram-negative bacteria can communicate with eukaryotic cells or bacteria via 60 – 90 nm in diameter membrane tubules formed from the outer membrane of bacteria.