Glioblastoma multiforme is the most common and lethal primary
brain cancer in adults.
Tumor cells diffusely infiltrate the brain making focal surgical and
radiation treatment challenging. The invasion of
glioma cells into normal brain is facilitated by the activity of
ion channels aiding dynamic regulation of cell volume. Recent studies have specifically implicated ClC-3, a voltage-gated
chloride channel, in this process. However, the interaction between ClC-3 activity and cell movement is poorly understood. Here, we demonstrate that ClC-3 is highly expressed on the plasma membrane of human
glioma cells where its activity is regulated through phosphorylation via
Ca(2+)/calmodulin-dependent protein kinase II (
CaMKII). Intracellular infusion of autoactivated
CaMKII via patch pipette enhanced
chloride currents 3-fold, and this regulation was inhibited by
autocamtide-2 related inhibitory
peptide, a CaMKII-specific inhibitor.
CaMKII modulation of
chloride currents was also lost upon stable
small hairpin RNA knockdown of ClC-3 channels indicating a specific interaction of ClC-3 and
CaMKII. In ClC-3-expressing cells, inhibition of
CaMKII reduced
glioma invasion to the same extent as direct inhibition of ClC-3. The importance of the molecular interaction of ClC-3 and
CaMKII is further supported by our finding that
CaMKII co-localizes and co-immunoprecipitates with ClC-3. ClC-3 and
CaMKII also co-immunoprecipitate in tissue biopsies from patients diagnosed with grade IV
glioblastoma. These
tumor samples show 10-fold higher ClC-3
protein expression than nonmalignant brain. These data suggest that
CaMKII is a molecular link translating intracellular
calcium changes, which are intrinsically associated with
glioma migration, to changes in ClC-3 conductance required for cell movement.