GABA B R-Induced EGFR Transactivation Promotes Migration of Human Prostate Cancer Cells

G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) act in concert to regulate cell growth, proliferation, survival, and migration. Metabotropic GABA receptor (GABA R) is the GPCR for the main inhibitory neurotransmitter GABA in the central nervous system. Increased expression of GABA R has been detected in human cancer tissues and cancer cell lines, but the role of GABA R in these cells is controversial and the underlying mechanism remains poorly understood. Here, we investigated whether GABA R hijacks RTK signaling to modulate the fates of human prostate cancer cells. RTK array analysis revealed that the GABA R-specific agonist baclofen selectively induced the transactivation of EGFR in PC-3 cells. EGFR transactivation resulted in the activation of ERK1/2 by a mechanism that is dependent on G protein and that requires matrix metalloproteinase-mediated proligand shedding. Positive allosteric modulators (PAMs) of GABA R, such as CGP7930, rac-BHFF, and GS39783, can function as PAM agonists to induce EGFR transactivation and subsequent ERK1/2 activation. Moreover, both baclofen and CGP7930 promoted cell migration and invasion through EGFR signaling. In summary, our observations demonstrated that GABA R transactivated EGFR in a ligand-dependent mechanism to promote prostate cancer cell migration and invasion, thus providing new insights into developing a novel strategy for prostate cancer treatment by targeting neurotransmitter signaling.