ABSTRACT
Aim To generate m3AChR-G11 fusion protein in baculovirus-Sf9 cells and test the couping function,the interation and the influence factors be-tween m3AChR and G11 protein,as well as screen the specific ligands for m3AChR. Methods m3AChR-G11 fused DNA was generated through a two-step PCR and then expressed in Sf9 cells to produce fusion protein. The total concentration for membrane protein was de-tected by BCA method,[3H]QNB and [35 S]GTP?S binding experiment as perfomed to study the function of m3AChR-G11 fusion protein. Results The expression level of m3AChR-G11 was 7. 76 ? 10 -9 mol?g -1. The affinity of GDP to G11 partner changed in the presence of different muscarinic ligands. IC50 values of GDP in the presence of ACh,Pilo,CCh,MCN-A-343,Atro,4-Damp and Dafi were 82. 2,93. 70,12. 10,14. 30, 1. 93,1. 37,0. 72 ? 10 -6 mol ? L -1 respectively,and that in the absence of muscarinic was 1. 99 ? 10 -6 mol ?L-1.Concluslons The m3AChR-G11 fusion protein has the pharmacological specificity of m3 receptor and the efficient coupling interaction of the two partners. Affinity of GDP to ligand-bound fusion protein represents the species of muscarinic ligands. This is helpful in screening and detecting the new specific ligands to muscarinic receptors.
ABSTRACT
After the development of two major techniques - SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) to image the human subjects in a three-dimensional direction in the 1980s, many radiotracers have been used for functional neuroimaging. Still it would be very important study to develop selective radiotracers for functional neuroimaging. New radiotracers will help to expand the knowledge of neurotransmitter systems and of the genetic contribution to receptor or transporter availability. Neurotransmitter depletion-restoration studies, the distribution of brain functions and their modulation by neurotransmitter system aid in better understanding and limiting the side effects of drugs used as well as newly developed. In addition, these radiotracers will be thus very useful to gain a better understanding in biochemical and pharmacological interactions in living human. This review mentions the introduction of radioligands for the functional neuroimaging. Although significant progress has been achieved in the development of new PET and SPECT ligands for in vivo imaging of those receptors and transporters, there are continuous needs of new diagnostic radioligands.