Abstract
ANO1, a Ca2+-activated chloride channel, is highly expressed in glioblastoma cells and its surface expression is involved in their migration and invasion. However, the regulation of ANO1 surface expression in glioblastoma cells is largely unknown. In this study, we found that Ca2+/Calmodulin-dependent protein kinase II (CaMKII) β specifically enhances the surface expression and channel activity of ANO1 in U251 glioblastoma cells. When KN-93, a CaMKII inhibitor, was used to treat U251 cells, the surface expression and channel activity of ANO1 were significantly reduced. Only CaMKIIβ, among the four CaMKII isoforms, increased the surface expression and channel activity of ANO1 in a heterologous expression system. Additionally, gene silencing of CaMKIIβ suppressed the surface expression and channel activity of ANO1 in U251 cells. Moreover, gene silencing of CaMKIIβ or ANO1 prominently reduced the migration and invasion of U251 and U87 MG glioblastoma cells. We thus conclude that CaMKIIβ plays a specific role in the surface expression of ANO1 and in the ANO1-mediated tumorigenic properties of glioblastoma cells, such as migration and invasion.
Highlights
Glioblastoma is the most common and lethal type of primary brain tumor [1,2]
Since ANO1 surface expression and chloride currents were regulated by CaMKIIβ in U251 cells, we examined whether gene silencing of CaMKIIβ or ANO1 affect the characteristics of cancer cells, such as invasion and migration
We previously reported that the surface expression and channel activity of ANO1 are critical for Cumulatively, these results strongly suggest that suppression of ANO1 surface expression by knockdown of CaMKIIβ is critical in the progression of human glioblastoma
Summary
Glioblastoma (astrocytomas, WHO grade IV) is the most common and lethal type of primary brain tumor [1,2]. CaMKII proteins are encoded by four genes: CAMK2A, CAMK2B, CAMK2G, and CAMK2D, which produce CaMKIIα, CaMKIIβ, CaMKIIγ, and CaMKIIδ, respectively [25] These CaMKII proteins phosphorylate nearly 40 different proteins, including enzymes, kinases, transcription factors, and ion channels [26,27,28]. Recent studies reported that the channel activity of ANO1 is inhibited by CaMKII-dependent phosphorylation. We found that surface expression and channel activity of ANO1 are enhanced in a CaMKIIβ-specific manner in U251 and U87 MG glioblastoma cells. We found that suppression of CaMKIIβ using small interfering RNA (siRNA) or a CaMKII inhibitor, KN-93, reduced the surface expression and channel activity of ANO1 in glioblastoma cells. Our results provide strong evidence for a CaMKIIβ-dependent regulation mechanism of ANO1 surface expression and indicate potential therapeutic targets against ANO1-mediated tumorigenesis in glioblastoma cells
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