The coreceptor function of CD44v6 is independent of heparin sulfation. (A) HUVECs were induced with VEGF-A121 in the presence of the CD44v6-specific peptide or control peptide as indicated. The activation of VEGFR-2 (as in Figure 1C) and Erk was determined. The IgG lane corresponds to an immunoprecipitation with the IgG control antibody. (B) HEK293 cells were transiently transfected with a VEGFR-2 expression construct (see “Transfection”). They were then treated with VEGF and peptides as indicated, and the activation of VEGFR-2 or signaling to Erk was measured directly by Western blotting. (C) BSp73AS cells (AS) or BSp73ASs6 (ASs6) cells were transiently transfected with a VEGFR-2 expression construct and activated with VEGF-A165 where indicated. Activation of VEGFR-2 was determined using the phospho VEGFR-2–specific antibody (Tyr 1175) directly in Western blotting. The numbers refer to fold induction. Vertical lines have been inserted to indicate repositioned gel lanes.