NHE1 promotes invadopodial ECM proteolysis through acidification of the peri‐invadopodial space

Abstract

Extracellular matrix (ECM) degradation is a critical process in tumor cell invasion and requires membrane and released proteases focalized at membrane structures called invadopodia. While extracellular acidification is important in driving tumor invasion, the structure/function mechanisms underlying this regulation are still unknown. Invadopodia are similar in structure and function to osteoclast podosomes responsible for bone degradation, and extracellular acidification is central to podosome action, suggesting that it could also be for invadopodial function. Here, utilizing a novel system for in situ zymography in native matrices, we show that the Na(+)/H(+) exchanger (NHE1) and NHE1-generated extracellular acidification are localized at and necessary for invadopodial-dependent ECM degradation, thereby promoting tumor invasion. Stimulation with EGF increased both NHE1-dependent proton secretion and ECM degradation. Manipulation of the NHE1 expression by RNA interference or activity via either transport-deficient mutation or the specific inhibitor cariporide confirmed that NHE1 expression and activity are required for invadopodia-mediated ECM degradation. Taken together, our data show a concordance among NHE1 localization, the generation of a well-defined acidic extracellular pH in the nanospace surrounding invadopodia, and matrix-degrading activity at invadopodia of human malignant breast carcinoma cells, providing a structural basis for the role of NHE1 in invasion and identifying NHE1 as a strategic target for therapeutic intervention.

NaV1.5 enhances breast cancer cell invasiveness by increasing NHE1-dependent H+ efflux in caveolae

“…Caveolae have been shown to contain NHE1 in other types of cells (Tekpli et al, 2008) and, independently, to be involved in breast cancer cell invasiveness (Yamaguchi et al, 2009). Recently, it has been shown that NHE1 is localized in invadopodia where it is responsible for an extracellular acidification and the degradation of the extracellular matrix (Busco et al, 2010). Our study brings a new mechanistic explanation for caveolae involvement in cancer cell invasiveness.…”

“…Na v 1.5 promotes NHE1-dependent invasiveness L Brisson et al cells to adapt to their high metabolic H þ production (Gatenby et al, 2007). Indeed it has been shown to have a predominant role in extracellular acidification of tumor cells (Bourguignon et al, 2004) and also to be involved in their invasive process (Cardone et al, 2005;Stock and Schwab, 2009;Busco et al, 2010). In this study, we showed for the first time the evidence that Na V 1.5 channels, abnormally expressed in breast cancer cells, functionally interact with NHE1 in caveolae to enhance its H þ -efflux activity and consequently promote acidic-dependent invasion of the extracellular matrix.…”

Defining the Na+/H+ exchanger NHE1 interactome in triple-negative breast cancer cells

“…These proteolytic enzymes digest a path through the extracellular matrix allowing for cells to leave the primary tumour and enter the bloodstream [24,25]. It is also of note that elevated NHE1 activity contributes of sodium loading of cells.…”

Na + /H + exchanger-mediated hydrogen ion extrusion as a carcinogenic signal in triple-negative breast cancer etiopathogenesis and prospects for its inhibition in therapeutics

“…NHE1 activity acidifies the peri-invadopodial space, establishing the optimal pH for the proteolytic activity of serine proteases and matrix metalloproteinases that aid in the digestion of extracellular matrix at the leading edge of invading cells (75,76) Of all the mutations to NHE1, though, S703A was the most remarkable. Cells expressing S703A-NHE1 exhibited a drastic change in morphology, seemingly reverting from their characteristic mesenchymal morphology to a more epithelial-like phenotype.…”