Membrane expression of OSTα requires the co-expression of OSTβ in COS7 cells. (A) COS7 cells were transfected with OSTα-FLAG and/or OSTβ-Myc as described in Methods and immunofluorescence was performed to visualize the localization of the individual subunits using mouse anti-FLAG and rabbit anti-Myc antibodies. Transfection of OSTα-FLAG (green) alone indicates that in the absence of OSTβ, OSTα is retained intracellularly (left row). In contrast, transfection of OSTβ (red) alone shows that this subunit can traffick to the plasma membrane without OSTα (middle row). Co-expression of OSTα and OSTβ subunits results in plasma membrane localization of OSTα (right row). Bar= 10 μM. (B) Transfected cells were also lysed with RIPA and lysates subjected to PAGE and Western blotting. When OSTα-FLAG and OSTβ-Myc were co-transfected a higher molecular weight band for OSTα was detected (arrow), suggesting a mature, glycosylated form of OSTα (B).