Endocytosis and signaling of 5-HT1A receptor

The neurotransmitter serotonin (also known as 5-hydroxytryptamine, 5-HT) regulates many important physiological as well as pathological functions in the body like psychoemotional, sensation, blood circulation, food intake, autonomic, memory, sleep, pain, etc. 5-HT binds to its receptor 5-HT1A to initiate GTP exchange at the Gi/o protein, which activates the receptor G protein complex. G protein subunits attach to different effectors and generate various responses, such as inhibition of adenyl cyclase enzyme and regulates the opening of Ca++ and K+ ion channels. Activated signalling cascades activate protein kinase C (PKC) (a second messenger), which further induces the detachment of Gβγ-dependent receptor signaling and leads to 5-HT1A internalization. After internalization, 5-HT1A receptor attaches to the Ras-ERK1/2 pathway. The receptor further trafficks to the lysosome for degradation. Receptor skips the trafficking to the lysosomal compartments and undergoes dephosphorylation. Dephosphorylated receptors now recycled back to the cell membrane. In this chapter, we have discussed the internalization, trafficking and signaling of the 5-HT1A receptor.