Surface expression of nonfunctional hASIC1a mutants. (A) Immunoblots of surface biotinylated HA WT and mutants with N- or C-terminal truncation at the indicated positions, total hASIC1a protein, and GAPDH protein in WCLs. The ctrl^neg sample is collected from nontransfected HEK293T cells; GAPDH is used as a loading control. Blots were incubated with anti–HA-HRP or anti–GAPDH-HRP antibody as indicated on the right. (B) Quantitative analysis of the immunoblots. Density values of the bands were measured using the ImageJ program. The ratio of the surface portion versus total amount in the WCL normalized to WT hASIC1a is shown as bars. (C) Immunoblots of surface expression of F21 hASIC1a mutants (biotinylated) compared to total lysate. (D) Similar experiment of W46 mutants.