The voltage-gated sodium channel β3 subunit modulates C6 glioma cell motility independently of channel activity

Background

Voltage-gated sodium channels (VGSCs) initiate action potentials in nerve and muscle cells and are regulated by auxiliary β subunits. VGSC β subunits are also expressed in some cancer types, suggesting potential functions distinct from their role in electrophysiological excitability. This study investigated the occurrence and functional implications of the VGSC β3 subunit (the product of SCN3B gene) in glioma, focusing on the role of its extracellular immunoglobulin domain (β3 Ig).

Methods

Data mining explored associations between β3 expression and glioma severity at patient, tissue, and single-cell levels. Using C6 glioma cells expressing β3 or β3 without its Ig domain, we examined the effects on cell viability, mobility, and actin-based cell protrusions. A single-chain variable fragment (scFv) antibody targeting the β3 Ig was selected by phage display to interfere with its functions. The interacting proteins with β3 Ig were identified by immunoprecipitation-mass spectrometry.

Results

Data mining revealed negative correlations between β3 expression and glioma severity and aggressiveness. Expression of β3 in C6 cells reduced cell migration and invasion without affecting cell viability. Filopodia were significantly increased while lamellipodia/ruffles were decreased, producing striking cell morphological changes. These effects were abrogated by expression of the β3 subunit lacking the β3 Ig domain or exogenous application of an scFv targeting β3 Ig. Most of the plasma membrane-associated proteins immunoprecipitated with the β3 subunit are known regulators of actin polymerization.

Conclusion

Our data reveals a novel and unexpected role for the VGSC β3 subunit in orchestrating actin organization and negatively regulating cell migration in glioma cells which may potentially explain clinical correlations with glioma severity.