An ASIC1 and ENaC hybrid channel is the amiloride sensitive channel in human glioma.

Abstract

High grade gliomas express multiple members of the Epithelial Sodium Channel (ENaC)/Degenerin (Deg) family, displaying a basally active amiloride sensitive cation current. We hypothesize that this glioma current is mediated by a hybrid channel composed of a mixture of Epithelial Sodium Channel (ENaC) and Acid Sensing Ion Channel (ASIC) subunits. Using immunohistochemisty we show a higher expression level of ASIC1, αENaC, and γENaC in glioblastoma biopsy tissue compared with non‐neoplastic brain tissue. To test our hypothesis we made dominant negative (DN) cDNAs for ASIC1, αENaC, and γENaC. D54‐MG cells transfected with the DN constructs for ASIC1, αENaC or γENaC showed reduced protein expression and a significant reduction in the amiloride sensitive whole cell current as compared with untransfected D54‐MG cells. Using co‐immunoprecipitation we show interactions between ASIC1, αENaC, and γENaC at the plasma membrane of D54‐MG cells, consistent with these subunits interacting with each other to form an ion channel. Data using Total Internal Resolution Fluorescent Microscopy (TIRFM) also suggest that ASIC1 and ASIC2 interact with γENaC in CHO‐K1 cells. These data suggest that different ENaC/Deg subunits combine to form a hybrid channel that likely underlies the amiloride‐sensitive current in human gliomas. This study was supported by NIH Grants CA101952 and DK037206.