Figure 1.

Agonist binding to GPCRs promotes the dissociation of GDP bound to the Gα subunit and its replacement with GTP leading to the activation of the heterotrimeric G proteins and the subunit dissociation into a βγ dimer and the GTP-bound α monomer. Both subunits activate multiple downstream effectors which induce gene transcription and relevant biological responses. A cross-talk between several GPCRs and other membrane receptors as Epidermal Growth Factor Receptor (EGFR) contributes to the growth stimulation and invasion of cancer cells.