Figure 6.

PROCR engages Src kinase to transactivate IGF-1R and other RTKs. a, Western blot showing that in BT549 cells with PROCR overexpression, inhibition of Src using KX2–391 diminishes the activities of Src, IGF-1R, EGFR-T845, and both ERK and PI3K–Akt–mTOR pathways, whereas it is ineffective to RhoA–ROCK signaling. b, Western blot analysis indicating that in MDA-MB-231 cells, knockdown of PROCR with two independent shRNAs attenuates the activity of EGFR at Tyr-845, but does not affect EGFR Tyr-1068 or Tyr-1173 phosphorylation. c, illustration of PROCR-dependent intracellular signaling pathways. Impact on EGFR-T845 activity is a subsequence of activation of Src by PROCR. d, Western blot showing that in BT549 cells with PROCR overexpression, incubation with IGF-1 neutralizing antibody (12 μg/ml, 2 h) could not inhibit IGF-1R, ERK, and Akt pathways induced by etopic PROCR. e, Western blot showing that in MDA-MB-231 cells, incubation with IGF-1 neutralizing antibody (12 μg/ml, 2 h) is sufficient to inhibit endogenous IGF-1R activity. Western blots in the same panel are from the same batch of cells using the same loadings, thus only one loading control is shown. For a better illustration, they are shown as three or four separated columns representing ERK, Akt, and RhoA pathways, respectively. Each experiment was repeated three times or more.