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Cx43 and Associated Cell Signaling Pathways Regulate Tunneling Nanotubes in Breast Cancer Cells.

ABSTRACT: Connexin 43 (Cx43) forms gap junctions that mediate the direct intercellular diffusion of ions and small molecules between adjacent cells. Cx43 displays both pro- and anti-tumorigenic properties, but the mechanisms underlying these characteristics are not fully understood. Tunneling nanotubes (TNTs) are long and thin membrane projections that connect cells, facilitating the exchange of not only small molecules, but also larger proteins, organelles, bacteria, and viruses. Typically, TNTs exhibit increased formation under conditions of cellular stress and are more prominent in cancer cells, where they are generally thought to be pro-metastatic and to provide growth and survival advantages. Cx43 has been described in TNTs, where it is thought to regulate small molecule diffusion through gap junctions. Here, we developed a high-fidelity CRISPR/Cas9 system to knockout (KO) Cx43. We found that the loss of Cx43 expression was associated with significantly reduced TNT length and number in breast cancer cell lines. Notably, secreted factors present in conditioned medium stimulated TNTs more potently when derived from Cx43-expressing cells than from KO cells. Moreover, TNT formation was significantly induced by the inhibition of several key cancer signaling pathways that both regulate Cx43 and are regulated by Cx43, including RhoA kinase (ROCK), protein kinase A (PKA), focal adhesion kinase (FAK), and p38. Intriguingly, the drug-induced stimulation of TNTs was more potent in Cx43 KO cells than in wild-type (WT) cells. In conclusion, this work describes a novel non-canonical role for Cx43 in regulating TNTs, identifies key cancer signaling pathways that regulate TNTs in this setting, and provides mechanistic insight into a pro-tumorigenic role of Cx43 in cancer.

SUBMITTER: Tishchenko A

PROVIDER: S-EPMC7601615 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Cx43 and Associated Cell Signaling Pathways Regulate Tunneling Nanotubes in Breast Cancer Cells.

Tishchenko Alexander A Azorín Daniel D DD Vidal-Brime Laia L Muñoz María José MJ Arenas Pol Jiménez PJ Pearce Christopher C Girao Henrique H Ramón Y Cajal Santiago S Aasen Trond T

Cancers 20200929 10

Connexin 43 (Cx43) forms gap junctions that mediate the direct intercellular diffusion of ions and small molecules between adjacent cells. Cx43 displays both pro- and anti-tumorigenic properties, but the mechanisms underlying these characteristics are not fully understood. Tunneling nanotubes (TNTs) are long and thin membrane projections that connect cells, facilitating the exchange of not only small molecules, but also larger proteins, organelles, bacteria, and viruses. Typically, TNTs exhibit ...[more]

PMID: 33003486

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Project description:Various types of intercellular connections that are essential for communication between cells are often utilized by pathogens. Recently, a new type of cellular connection, consisting of long, thin, actin-rich membrane extensions named tunneling nanotubes (TNTs), has been shown to play an important role in cell-to-cell spread of HIV and influenza virus. In the present report, we show that TNTs are frequently formed by cells infected by an alphaherpesvirus, bovine herpesvirus 1 (BoHV-1). Viral proteins, such as envelope glycoprotein E (gE), capsid protein VP26, and tegument protein Us3, as well as cellular organelles (mitochondria) were detected by immunofluorescence and live-cell imaging of nanotubes formed by bovine primary fibroblasts and oropharynx cells (KOP cells). Time-lapse confocal studies of live cells infected with fluorescently labeled viruses showed that viral particles were transmitted via TNTs. This transfer also occurred in the presence of neutralizing antibodies, which prevented free entry of BoHV-1. We conclude that TNT formation contributes to successful cell-to-cell spread of BoHV-1 and demonstrate for the first time the participation of membrane nanotubes in intercellular transfer of a herpesvirus in live cells.IMPORTANCE Efficient transmission of viral particles between cells is an important factor in successful infection by herpesviruses. Herpesviruses can spread by the free-entry mode or direct cell-to-cell transfer via cell junctions and long extensions of neuronal cells. In this report, we show for the first time that an alphaherpesvirus can also spread between various types of cells using tunneling nanotubes, intercellular connections that are utilized by HIV and other viruses. Live-cell monitoring revealed that viral transmission occurs between the cells of the same type as well as between epithelial cells and fibroblasts. This newly discovered route of herpesviruses spread may contribute to efficient transmission despite the presence of host immune responses, especially after reactivation from latency that developed after primary infection. Long-range communication provided by TNTs may facilitate the spread of herpesviruses between many tissues and organs of an infected organism.

Project description:BACKGROUND: Tunneling nanotubes (TNTs) may offer a very specific and effective way of intercellular communication. Here we investigated TNTs in the human retinal pigment epithelial (RPE) cell line ARPE-19. Morphology of TNTs was examined by immunostaining and scanning electron microscopy. To determine the function of TNTs between cells, we studied the TNT-dependent intercellular communication at different levels including electrical and calcium signalling, small molecular diffusion as well as mitochondrial re-localization. Further, intercellular organelles transfer was assayed by FACS analysis. METHODOLOGY AND PRINCIPAL FINDINGS: Microscopy showed that cultured ARPE-19 cells are frequently connected by TNTs, which are not attached to the substratum. The TNTs were straight connections between cells, had a typical diameter of 50 to 300 nm and a length of up to 120 µm. We observed de novo formation of TNTs by diverging from migrating cells after a short time of interaction. Scanning electron microscopy confirmed characteristic features of TNTs. Fluorescence microscopy revealed that TNTs between ARPE-19 cells contain F-actin but no microtubules. Depolymerisation of F-actin, induced by addition of latrunculin-B, led to disappearance of TNTs. Importantly, these TNTs could function as channels for the diffusion of small molecules such as Lucifer Yellow, but not for large molecules like Dextran Red. Further, organelle exchange between cells via TNTs was observed by microscopy. Using Ca²? imaging we show the intercellular transmission of calcium signals through TNTs. Mechanical stimulation led to membrane depolarisation, which expand through TNT connections between ARPE-19 cells. We further demonstrate that TNTs can mediate electrical coupling between distant cells. Immunolabelling for Cx43 showed that this gap junction protein is interposed at one end of 44% of TNTs between ARPE-19 cells. CONCLUSIONS AND SIGNIFICANCE: Our observations indicate that human RPE cell line ARPE-19 cells communicate by tunneling nanotubes and can support different types of intercellular traffic.

Dataset Information

Cx43 and Associated Cell Signaling Pathways Regulate Tunneling Nanotubes in Breast Cancer Cells.

Publications

Cx43 and Associated Cell Signaling Pathways Regulate Tunneling Nanotubes in Breast Cancer Cells.

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