N-Glycan and Heparan Sulphate Components of the Extracellular Matrix are Essential for Laminar Shear Stress Response of the Epithelial Sodium Channel (ENaC)

The epithelial sodium channel (ENaC), a mechanosensitive ion channel, is known to be activated by laminar shear stress (LSS) [1]. We hypothesise that the large extracellular loops of ENaC interact with the complex extracellular matrix (ECM) and that the application of LSS deforms both the extracellular matrix (ECM) and the interacting ENaC components resulting in a change in ENaC activity. This study investigated whether or not the N-glycan and heparan sulphate components of the ECM are specifically involved in the LSS activation of ENaC. Human α, β and γ ENaC subunits were co-expressed in oocytes surgically harvested from female Xenopus laevis. Two-electrode voltage-clamp was used to determine ENaC activity in response to LSS when different components of the ECM were degraded by neuraminidase and heparinase III enzymes. A significant LSS response was observed in ENaC expressing oocytes, compared to native (no ENaC) oocytes; normalized LSS current of 5.5 ± 1.1 compared to 0.06 ± 0.03 (p = 0.003, n =8–14)....