Mechanism Of GABA_B Receptor Mobility On Cell Membrane

GABABreceptors are members of class C family of G protein coupled receptors, andtheir ligand is inhibitory neurotransmitter gamma-aminobutyric acid(GABA) of the centralnervous system. GABABreceptors consist of GABAB1and GABAB2subunits. GABABreceptors are widely distributed in mammalian central nervous system and peripheralnervous system and medicated slow synaptic inhibition in the brain.Previous researches in our lab showed that GABABreceptors are located in lipid raftsin the resting state of the cell, and the palmitoylation of GABAB2C-tail plays an importantrole in it. When the GABABreceptors have been activated, they will transfer out of lipidrafts. Receptors associated with lipid rafts have a significant influence on its signaltransduction. Whether the activity of the receptors can dynamically regulate thepalmitoyation of GABABreceptors and palmitoylation can regulate the receptors throughother post-translation protein modifications, there is not much research about it.In HEK293cells and CGNs, through the ABE experiments, we found that the Cys874on the GABAB2C-tail could occur the palmitoylation, which is regulated by the activity ofthe receptors. When the GABABreceptors have been activated, the palmitoylation of thereceptors will be reduced, and at the same time GABABR will transfer out of lipid. Throughthe sequence analysis, we found that near the Cys874of the GABAB2C-tail is YQEL,which is mostly AP2binding motif, and the Y may be a potential phosphorylation site ofnon-receptor tyrosine kinase. So we speculate that palmitoylation of GABABreceptors onthe GABAB2C-tail ensures proper surface location and increases the stability of GABABreceptors in the cell surface via tyrosine phosphorylation of tyrosine based internalizationmotifs. Studies have shown that GABAB2C-tail is playing a dominant role in regulating theinternalization of GABABreceptors in live cells. Our results further prove that when wemutated sites of GABAB2C-tail YQEL, it will block the internalization of receptors anddestroy the interaction with receptors and non-receptor tyrosine kinase. So we got a conclusion that Tyrsine830may be the phosphorylation site and its interaction withpalmitoylation of Cys874will influence the receptors constitutive internalization. And thisnew found will provides us a new basis to research mobility mechanism of GABABR on theplasma membrane.