Animal cells connected by nanotubes can be electrically coupled through interposed gap-junction channels

Abstract

Tunneling nanotubes (TNTs) are recently discovered conduits for a previously unrecognized form of cell-to-cell communication. These nanoscale, F-actin-containing membrane tubes connect cells over long distances and facilitate the intercellular exchange of small molecules and organelles. Using optical membrane-potential measurements combined with mechanical stimulation and wholecell patch-clamp recording, we demonstrate that TNTs mediate the bidirectional spread of electrical signals between TNT-connected normal rat kidney cells over distances of 10 to 70 μm. Similar results were obtained for other cell types, suggesting that electrical coupling via TNTs may be a widespread characteristic of animal cells. Strength of electrical coupling depended on the length and number of TNT connections. Several lines of evidence implicate a role for gap junctions in this long-distance electrical coupling: punctate connexin 43 immunoreactivity was frequently detected at one end of TNTs, and electrical coupling was voltage-sensitive and inhibited by meclofenamic acid, a gap-junction blocker. Cell types lacking gap junctions did not show TNT-dependent electrical coupling, which suggests that TNT-mediated electrical signals are transmitted through gap junctions at a membrane interface between the TNT and one cell of the connected pair. Measurements of the fluorescent calcium indicator X-rhod-1 revealed that TNTmediated depolarization elicited threshold-dependent, transient calcium signals in HEK293 cells. These signals were inhibited by the voltage-gated Ca 2+ channel blocker mibefradil, suggesting they were generated via influx of calcium through low voltage-gated Ca 2+ channels. Taken together, our data suggest a unique role for TNTs, whereby electrical synchronization between distant cells leads to activation of downstream target signaling.

Electrotonic coupling of excitable and nonexcitable cells in the heart revealed by optogenetics

“…Plausible structural substrates for heterocellular electrotonic coupling include previously identified connexin-based junctions between cardiac myocytes and nonmyocytes in situ (5) but potentially also tunneling nanotubes (27). These direct membrane connections have been shown to support heterocellular communication (28), including electrotonic coupling (29), in vitro. To investigate 3D nanoscale interrelations of myocytes and nonmyocytes at the scar border of cryoinjured hearts, tissue samples were imaged by electron tomography (ET) with an isotropic voxel size of 1.02-2.55 nm.…”

Contractility in Type III Cochlear Fibrocytes Is Dependent on Non-muscle Myosin II and Intercellular Gap Junctional Coupling

“…4D; n=5), confirming that neurobiotin and Lucifer yellow had most likely transferred between cells via gap junctions and not via cytoplasmic bridges. In experiments in which cells were pre-treated with meclofenamic acid (MFA), a water-soluble blocker of cx43-containing gap junctions (Pan et al 2007;Liu et al 2010;Wang et al 2010), there was no spread of neurobiotin ( Fig. 4E; n=4).…”

“…Dye transfer within cultures was inhibited by MFA, a reversible blocker of cx43-containing channels in various tissues (Harks et al 2001;Pan et al 2007;Liu et al 2010;Wang et al 2010). This agent has been reported to modulate inter-kinetic nuclear migration (INM), via its inhibition of gap junctional signaling and the resultant regulation of the cytoskeleton (Liu et al 2010).…”

How the Internet of cells has biologists buzzing

“…Further types of tube have been spotted as well. In 2010, Gerdes and his team reported that some tubes end in gap junctions: gateways that bestow the neuron-like ability to send electrical signals and can also pass along peptides and RNA molecules 6 . Yamashita speculates that such connections may be more than conceptually related to neuronal synapses.…”