GABAB Receptor Activation Protects Neurons from Apoptosis via IGF-1 Receptor Transactivation

The G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) play key roles in cell-cell communication. Several studies revealed important synergisms between these two types of receptors, with some of the actions of either receptor being mediated through transactivation of the other. Among the large GPCR family, GABA(B) receptor is activated by the neurotransmitter GABA, and is expressed in most neurons where it mediates slow and prolonged inhibition of synaptic transmission. Here we show that this receptor is involved in the regulation of life and death decisions of cerebellar granule neurons (CGNs). We show that specific activation of GABA(B) receptor can protect neurons from apoptosis through a mechanism that involves transactivation of the IGF-1 receptor (IGF-1R). Further work demonstrated that this cross talk was dependent on G(i/o)-protein, PLC, cytosolic Ca2+, and FAK1 but independent of PKC, while IGF-1R-induced signaling involved Src kinase, PI3 kinase, and Akt activation. These results reveal a new function for this important GPCR and further highlight the importance of functional cross-talk networks between GPCRs and RTKs. Our results reveal GABA(B) receptor as a potential drug target for the treatment of neurodegenerative disorders.