Neither R124H nor V270E NIS interferes with WT NIS activity when coexpressed with WT NIS.
A, Steady-state I− uptake in Cos-7 cells transiently transfected with the GFP-expressing vector pEGFP (Clontech), WT NIS, or one of the NIS mutants R124H and V270E (5 μg/10 cm dish). In WT/GFP-, WT/R124H-, WT/V270E-, and V270E/R124H-cotransfected cells, a half dose of each of the plasmids was used (2.5 μg/10 cm dish), to keep the total amount of DNA constant. Cells were incubated with 10μM I− in the absence (dark bars) or presence (light bars) of 40μM ClO4−. Results are expressed in pmol I−/μg of DNA ± SD. *, P < .05 (ANOVA, Newman-Keuls test). ns, nonstatistically significant. B, Representative FACS analysis of WT or mutant NIS expression under nonpermeabilized (upper panel; surface) and permeabilized (lower panel; total) conditions using anti-HA antibody. Cos-7 cells transiently transfected with HA-tagged WT NIS, HA-tagged R124H, HA-tagged V270E NIS, and HA-tagged V270E + nontagged R124H NIS (2.5 μg per mutant/10-cm dish). A vector encoding the Na+/monocarboxylate transporter (SMCT) was added to adjust for equal amounts of transfected DNA.
