Figure 5. Signal transduction in the tumor cell from the NTSR₁ receptor.

In general, the activation of NTSR₁ leads to activation of ERK1/2 MAPK and PI3K-PKB cascades. The signal transmission involves EGFR, activated via c-Src. EGFR can also be activated by MMP1 and MMP9. These metalloproteins release the EGF-like ligands, thus activating these receptors. As a result, the ERK1/2 MAPK cascade and the PI3K-PKB pathway are activated. Nevertheless, the ERK1/2 MAPK cascade can be directly activated by the NTSR₁-PLCβ-PKC pathway, without the involvement of other receptors. Similarly, the PI3K-PKB pathway can be activated by signal transduction to IGF-1R.