Large scale expression and purification of the rat 5-HT2c receptor

5-HT2c G-protein coupled receptors located in the central nervous system bind the endogenous neurotransmitters serotonin and couple to G protein to mediate excitatory neurotransmission, which inhibits dopamine and norepinephrine release in the brain. Thus, 5-HT2c receptors play important roles in cognitive function and are potent drug targets. Structural information is needed to elucidate the molecular mechanism of ligand-binding and receptor-activation of the 5-HT2c receptor. Lacking of an efficient expression system that produces sufficient amounts of active and homogenous receptors hinders progress in the functional and structural characterization of the 5-HT2c receptor. We present here a protocol which can be used easily to obtain milligram amount of purified rat 5-HT2c receptors. We established this protocol by protein engineering and optimization of expression and purification based on radioligand-binding assay. The purified and well-characterized rat 5-HT2c receptors are active, stable, homogenous, and ready for 2-dimensional and 3-dimensional crystallization experiments.