FIGURE 3.

TSP-2 and TSP-4 EGF-like repeats activate EGFR. A431 cells were exposed to equimolar concentrations (214 nm) of TSP1 (lane 2), recombinant EGF-like repeats from TSP1 (lane 3), TSP-2 (lanes 4 and 5), and TSP-4 (lanes 6 and 7) or media alone (lane 1). These baculovirus-derived recombinant proteins included the following: TSP1 E123 (lane 3), TSP-2 E123CaG (lane 4), TSP-2 P3E123 (lane 5), TSP-4 E1234 (lane 6), and TSP-4 E1234CaG (lane 7). Cells were lysed and processed for immunoblotting with anti-phospho-EGFR (Tyr-1068) antibodies. The blots were stripped and reprobed with anti-β-tubulin antibody to indicate protein loading and transfer. IB, immunoblot; IB^*, immunoblot after stripping. The blot is representative of ≥3 independent experiments.