Tunneling nanotube (TNT)-like structures facilitate a constitutive, actomyosin-dependent exchange of endocytic organelles between normal rat kidney cells

Abstract

Tunneling nanotube (TNT)-like structures are intercellular membranous bridges that mediate the transfer of various cellular components including endocytic organelles. To gain further insight into the magnitude and mechanism of organelle transfer, we performed quantitative studies on the exchange of fluorescently labeled endocytic structures between normal rat kidney (NRK) cells. This revealed a linear increase in both the number of cells receiving organelles and the amount of transferred organelles per cell over time. The intercellular transfer of organelles was unidirectional, independent of extracellular diffusion, and sensitive to shearing force. In addition, during a block of endocytosis, a significant amount of transfer sustained. Fluorescence microscopy revealed TNT-like bridges between NRK cells containing F-actin but no microtubules. Depolymerization of F-actin led to the disappearance of TNT and a strong inhibition of organelle exchange. Partial ATP depletion did not affect the number of TNT but strongly reduced organelle transfer. Interestingly, the myosin II specific inhibitor S-(-)-blebbistatin strongly induced both organelle transfer and the number of TNT, while the general myosin inhibitor 2,3-butanedione monoxime induced the number of TNT but significantly inhibited transfer. Taken together, our data indicate a frequent and continuous exchange of endocytic organelles between cells via TNT by an actomyosin-dependent mechanism.

TiO2nanotube stimulate chondrogenic differentiation of limb mesenchymal cells by modulating focal activity

“…Several recent studies showed that a nanotubebearing surface allows dynamic and coordinated changes in cytoskeletal organization, locomotion, and cell-to-cell communication in a great variety of cell systems, including dendritic cells, monocytes, human embryonic kidney 293T cells, normal rat kidney cells, primary macrophages, T cells, activated B cells, and human glioblastoma cells (Ryu et al, 2005;Dumortier et al, 2006;Brammer et al, 2008;Gurke et al, 2008;Kaiser et al, 2008;Williams et al, 2008;Park et al, 2009). Since morphological transition via reorganization of the actin cytoskeleton is essential for chondrocytic differentiation, we hypothesized that a nanotubebearing surface could be a useful culture substrate for maintaining chondrocytic phenotypes and allowing chondrocytes to differentiate.…”

Tunneling-nanotube development in astrocytes depends on p53 activation

“…1 It is hypothesized that TNTs are kind of a 'highway' for substance transportation between cells. 24 Cellular compartments, such intracellular and extracellular Ab peptides, which are proven cytotoxic to neurons and astrocytes. 19,25 As a transcription factor, p53 responds to various stress signals and transcribes a series of genes.…”

Tunneling nanotubes: Emerging view of their molecular components and formation mechanisms

“…The organelle transfer in PC12 and NRK cells is unidirectional and dependent on actin filaments [7], and is inhibited by ATP depletion and the general myosin inhibitor 2,3-butanedione monoxime [17]. In addition, the actin-based molecular motor, myosin-Va, co-localizes with organelles inside the TNTs of PC12 and rat primary 13 astrocytes cells [7] [18], suggesting that this motor protein is an interesting potential candidate to mediate movement of organelles along TNT.…”