FIGURE 8.

The extracellular domains of HER2 and EGFR interact directly with Sdc1 and Sdc4, respectively. A, recombinant HER2^ecto expressed and purified from S2 insect cell conditioned medium is incubated overnight with recombinant GST, GST-S1ED with or without SSTN_210–240 or with GST-S4ED, then the GST fusion proteins are captured on glutathione beads and probed for binding of HER2^ecto. An equivalent amount of HER2^ecto used in the capture assay is shown as input. B, recombinant EGFR^ecto expressed in insect cells is incubated overnight with recombinant GST, GST-S4ED with or without SSTN_87–131 or with GST-S1ED, then the GST fusion proteins are captured on glutathione beads and probed for binding of EGFR^ecto. An equivalent amount of EGFR^ecto used in the capture assay is shown as input.