Voltage-gated sodium (Na_V) channels are heteromeric proteins consisting of a single pore forming α-subunit associated with one or two auxiliary β-subunits. These channels are classically known for being responsible of action potential generation and propagation in excitable cells; but lately they have been reported as widely expressed and regulated in several human cancer types. We have previously demonstrated the overexpression of Na_V1.6 channel in cervical cancer (CeCa) biopsies and primary cultures, and its contribution to cell migration and invasiveness. Here, we investigated the expression of Na_V channels β-subunits (Na_Vβs) in the CeCa cell lines HeLa, SiHa and CaSki, and determined their contribution to cell proliferation, migration and invasiveness.

We assessed the expression of Na_Vβs in CeCa cell lines by performing RT-PCR and western blotting experiments. We also evaluated CeCa cell lines proliferation, migration, and invasion by in vitro assays, both in basal conditions and after inducing changes in Na_Vβs levels by transfecting specific cDNAs or siRNAs. The potential role of Na_Vβs in modulating the expression of Na_V α-subunits in the plasma membrane of CeCa cells was examined by the patch-clamp whole-cell technique. Furthermore, we investigated the role of Na_Vβ1 on cell cycle in SiHa cells by flow cytometry.

We found that the four Na_Vβs are expressed in the three CeCa cell lines, even in the absence of functional Na_V α-subunit expression in the plasma membrane. Functional in vitro assays showed differential roles for Na_Vβ1 and Na_Vβ4, the latter as a cell invasiveness repressor and the former as a migration abolisher in CeCa cells. In silico analysis of Na_Vβ4 expression in cervical tissues corroborated the downregulation of this protein expression in CeCa vs normal cervix, supporting the evidence of Na_Vβ4’s role as a cell invasiveness repressor.

Our results contribute to the recent conception about Na_Vβs as multifunctional proteins involved in cell processes like ion channel regulation, cell adhesion and motility, and even in metastatic cell behaviors. These non-canonical functions of Na_Vβs are independent of the presence of functional Na_V α-subunits in the plasma membrane and might represent a new therapeutic target for the treatment of cervical cancer.