Synthesis of the interleukin-4Rα/GP Ibα subunit is stabilized by the induction of GP Ibβ and GP IX genes.

Cell lysates of transfected CHO cells induced for the expression of GP Ibβ and GP IX (Tet-Off) were analyzed by Western blot to identify the IL-4Rα/GP Ibα subunit schematically shown in Figure 1. Under nonreducing conditions an anti–IL-4R monoclonal antibody identified a dominant immunoreactive species migrating with an apparent molecular mass of 148 kDa. No IL-4R immunoreactive species was seen in the absence of induced GP Ibβ and GP IX expression (Tet-On). Upon induction (Tet-Off) an anti-GP Ibβ polyclonal antibody identified a dominant immunoreactive species seen under nonreducing conditions with a similar mobility to the major antigen observed with an anti–IL-4R monoclonal antibody (mAb). Upon reduction a single immunoreactive species of approximately 22 kDa is seen, consistent with the reduced single chain molecular weight for the platelet GP Ibβ subunit.