GFP-ClC-1-FLAG channels expressed in myotubes function normally and traffic to the sarcolemma, but not to DHPR-containing peripheral junctions. (A) GFP-ClC-1-FLAG channels expressed in dyspedic myotubes exhibit normal voltage dependence of steady-state (open circles) and instantaneous (filled circles) current. (B) Superimposed and normalized (to current at −140 mV) instantaneous current–voltage relationships obtained from myotubes expressing either GFP-ClC-1-FLAG (filled circles) or ClC-1 (open triangles). (C) Average relative Po-V curves obtained from tail currents elicited at −100 mV for myotubes expressing GFP-ClC-1-FLAG (filled circles) or ClC-1 (open triangles). Smooth curves through each dataset were generated using a modified Boltzmann equation (Eq. 3). Data in A–C are presented as mean ± SEM of eight and seven experiments for GFP-ClC-1-FLAG– and ClC-1-IRES-GFP–expressing myotubes, respectively. GFP-ClC-1-FLAG fluorescence (D) does not colocalize with DHPR immunofluorescence (E), as emphasized in the merged image (F). In D, black arrows show intracellular aggregates, and white arrows show areas of uniform sarcolemmal expression. DHPRs reside in puncta representing peripheral junctions between the SR and sarcolemma.