With an increased probability that an agonist binds to a receptor,for example by increasing the agonist concentration or by prolongedexposure of the agonist to the receptor, the likelihood that the receptor will transition to a desensitized state also increases. Receptordesensitization is a conformational transition to a relatively stableand non-conducting agonist-bound state that has high ligand affinity.Parameters that characterize receptor desensitization include the rateof desensitization, the degree of inhibition caused by sustained agonist exposures as measured under equilibrium conditions, and therate of recovery from desensitization upon removal of the agonist.These parameters are highly dependent on the specific subunit composition of the nAChR, as well as on the chemical properties of theagonist ligand (reviewed by Giniatullin et al., 2005). The α and β subunits contribute differentially to the desensitization properties ofheteromeric receptors, by affecting the rate of desensitization andthe affinity for the desensitized state (Quick & Lester, 2002).Moreover, the desensitization of a receptor can further be influencedby kinase and phosphatase activity, suggesting the possibility ofdynamic modulation of receptor function (Quick & Lester, 2002)
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