Connexin43 enhances glioma invasion by a mechanism involving the carboxy terminus

Abstract

Gliomas are particularly difficult to cure owing largely to their invasive nature. The neoplastic changes of astrocytes which give rise to these tumors frequently include a reduction of connexin43 (Cx43), the most abundant connexin isoform expressed in astrocytes. Cx43 is a subunit of gap junctions (GJ), intercellular channels which directly link the cytosol of adjacent cells and allow the regulated passage of ions and small molecules. To examine the role of Cx43 in glioma motility, we identified two variant C6 cell lines which endogenously express high (C6-H) or low (C6-L) levels of Cx43. In wound healing and transwell assays, C6-H cells were more motile than C6-L cells. To deduce whether Cx43 mediated these differences, assays were conducted on C6-H cells retrovirally transduced with Cx43 shRNA. Coincident with the stable knockdown of endogenous Cx43, a decrease in motility and invasion was observed. Gap junctional intercellular communication was also decreased, however motility assays conducted in the presence of GJ inhibitors did not reveal significant differences in cell motility. C6 cells transfected with full length or C-terminal truncated Cx43 (Cx43DeltaCT) were subjected to the aforementioned motility assays to expose alternate mechanisms of Cx43-mediated motility. Cells expressing full length Cx43 exhibited increased motility while cells expressing Cx43DeltaCT did not. This report, the first in which RNAi has been employed to reduce Cx43 expression in gliomas, indicates that the downregulation of Cx43 decreases motility of C6 cells. Furthermore, it is the first report to suggest that the Cx43 CT plays an important role in glioma motility.

Connexins, cell motility, and the cytoskeleton

“…To address the role of the Cx43 CT, C6 cells were transfected with full length Cx43 and a Cterminal truncated Cx43 (Cx43DCT). Cells expressing full length Cx43 exhibited increased motility while motility of cells expressing Cx43DCT remained unchanged indicating the importance of the Cx43 CT in glioma motility [Bates et al, 2007].…”

“…By contrast, another study showed that blocking GJIC with CBX did not alter motility of C6 cells [Bates et al, 2007]. The latter authors examined the role of Cx43 in migration of C6 glioma cells with the help of two distinct C6 populations, one with high (C6-H) and one with low (C6-L) endogenous expression of Cx43.…”

“…Stable knock-down of Cx43 expression in C6-H glioma using shRNA decreased motility, tumor invasion and also GJIC. However, blocking GJIC with CBX did not alter C6 motility [Bates et al, 2007]. To address the role of the Cx43 CT, C6 cells were transfected with full length Cx43 and a Cterminal truncated Cx43 (Cx43DCT).…”

Connexin 43 (Cx43) Expression in Laryngeal Squamous Cell Carcinomas: Preliminary Data on Its Possible Prognostic Role

“…Experimental data have shown the role of Cx43 in the control of cell proliferation and apoptosis for its ability to form hemichannels exchanging apoptotic and cell growth factors between extracellular and intracellular matrix, but also its role in promoting tumor progression and metastasis [7]. Recent reports suggest a more complex role of Cx43 in the different stages of tumor progression [4,7,8]; Cx43 downregulation has been associated with development of cancer phenotype [2,9], while aberrant Cx43 upregulation in advanced stages of carcinomas suggests the possibility that cancer cells may communicate with normal host cells across hemichannels, playing a role in migration and growth of metastatic cells. Aberrant Cx43 expression has been detected in advanced stages of prostatic and colonic adenocarcinomas [8,10], and metastatic cutaneous melanoma [11].…”

Connexin 43 controls the multipolar phase of neuronal migration to the cerebral cortex

“…Recently, studies using Cx43cKO and Cx43k258stop mice have indicated that the C terminus is required for cortical neuronal migration (30). In addition, independent regulation of the gap junction channel or C-terminal domain in neurite outgrowth (31,32) and cellular motility (33)(34)(35)(36)(37) have been demonstrated in various cell types, indicating that they may affect the neocortical development (38).…”