NaV1.5 Na+ channels allosterically regulate the NHE-1 exchanger and promote the activity of breast cancer cell invadopodia

Abstract : The degradation of the extracellular matrix by cancer cells represents an essential step in metastatic progression and this is performed by cancer cell structures called invadopodia. Na V 1.5 (also known as SCN5A) Na + channels are overexpressed in breast cancer tumours and are associated with metastatic occurrence. It has been previously shown that Na V 1.5 activity enhances breast cancer cell invasiveness through perimembrane acidification and subsequent degradation of the extracellular matrix by cysteine cathepsins. Here, we show that Na V 1.5 colocalises with Na + /H + exchanger type 1 (NHE-1) and caveolin-1 at the sites of matrix remodelling in invadopodia of MDA-MB-231 breast cancer cells. NHE-1, Na V 1.5 and caveolin-1 co-immunoprecipitated, which indicates a close association between these proteins. We found that the expression of Na V 1.5 was responsible for the allosteric modulation of NHE-1, rendering it more active at the intracellular pH range of 6.4-7; thus, it potentially extrudes more protons into the extracellular space. Furthermore, Na V 1.5 expression increased Src kinase activity and the phosphorylation (Y421) of the actin-nucleation-promoting factor cortactin, modified F-actin polymerisation and promoted the acquisition of an invasive morphology in these cells. Taken together, our study suggests that Na V 1.5 is a central regulator of invadopodia formation and activity in breast cancer cells.