Membrane organization of the human serotonin<SUB>1A</SUB> receptor monitored by detergent insolubility using GFP fluorescence

Insolubility in non-ionic detergents such as Triton X-100 at low temperature is a widely used biochemical criterion for characterization of membrane domains. In view of the emerging role of membrane organization in the function of G-protein coupled receptors, we have examined detergent insolubility of the 5-HT1A receptor in CHO cells using a novel GFP fluorescence approach developed by us. Using this approach, we have explored the membrane organization of the serotonin1A receptor tagged to enhanced yellow fluorescent protein (5-HT1AR-EYFP) stably expressed in CHO-K1 cells under conditions of varying detergent concentration, reduced membrane cholesterol and agonist stimulation. Our results show that a small yet significant fraction of the 5-HT1A receptor exhibits detergent insolubility, which increases upon depletion of membrane cholesterol. Stimulation of 5-HT1AR-EYFP by its endogenous ligand, serotonin, did not cause a significant change in the detergent insolubility of the receptor. Taken together, our results on detergent insolubility of 5-HT1AR-EYFP provide new insights into the membrane organization of the 5-HT1A receptor and could be relevant in the analysis of membrane organization of other G-protein coupled receptors