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

Abstract

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). In ENaC expressing oocytes cleavage of N‐glycan from the ECM with neuraminidase (0.2U/mL for 2h at 21°C) significantly reduced the normalised LSS response from 4.5 ± 0.4 to 1.7 ± 0.4 (p=0.003, n=8). Destruction of heparan sulphate components of the ECM with heparinase III (0.5 U/mL for 30min at 21°C) significantly reduced the LSS response from 5.1 ± 1.2 to 1.2 ± 0.5 (p=0.009, n=12). Data indicates that both removal of N‐glycan and cleavage of heparan sulphate from the ECM reduce the activation of ENaC by LSS, indicating that they are crucial components of the ECM for mechanosensation by ENaC.Support or Funding InformationThis study was supported by the Royal Society Marsden fund.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.