Calcium entry via TRPC1 channels activates chloride currents in human glioma cells

Malignant gliomas are highly invasive brain cancers that carry a dismal prognosis. Recent studies indicate that Cl− channels facilitate glioma cell invasion by promoting hydrodynamic cell shape and volume changes. Here we asked how Cl− channels are regulated in the context of migration. Using patch-clamp recordings we show Cl− currents are activated by physiological increases of [Ca2+]i to 65 and 180 nM. Cl− currents appear to be mediated by ClC-3, a voltage-gated, CaMKII-regulated Cl− channel highly expressed by glioma cells. ClC-3 channels colocalized with TRPC1 on caveolar lipid rafts on glioma cell processes. Using perforated-patch electrophysiological recordings, we demonstrate that inducible knockdown of TRPC1 expression with shRNA significantly inhibited glioma Cl− currents in a Ca2+-dependent fashion, placing Cl− channels under the regulation of Ca2+ entry via TRPC1. In chemotaxis assays epidermal growth factor (EGF)-induced invasion was inhibition by TRPC1 knockdown to the same extent as pharmacological block of Cl− channels. Thus endogenous glioma Cl− channels are regulated by TRPC1. Cl− channels could be an important downstream target of TRPC1 in many other cells types, coupling elevations in [Ca2+]i to the shape and volume changes associated with migrating cells.