A single amino-acid in the TM1 domain is an important determinant of the desensitization kinetics of recombinant human and guinea pig alpha-homomeric 5-hydroxytryptamine type 3 receptors.
Desensitization of ligand-gated ion channels shapes synaptic responses and provides critical neuroprotection at central synapses, yet the molecular mechanisms underlying the desensitization process are poorly understood. Using the whole-cell voltage-clamp technique, we investigated desensitization kinetics of recombinant human and guinea pig alpha-homomeric 5-hydroxytryptamine type 3 (5-HT(3A)) receptors heterologously expressed in human embryonic kidney 293 cells. Human 5-HT(3A) receptors desensitize 3.5 times faster than does the homologous receptor from guinea pigs. By constructing various chimeras and through site-directed mutagenesis, we have identified a single serine in the M1 region of the human 5-HT(3A) receptor sequence (S248) that, when substituted with threonine found in the equivalent guinea pig sequence (T254), conferred guinea pig-like kinetics on the time course of desensitization of the human receptor. Correspondingly, the reverse mutation (guinea pig T254S) resulted in a fast, human-like time constant of desensitization. Thus, the primary structure of the M1 region is an important determinant of desensitization kinetics of recombinant 5-HT(3A) receptors.
Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany.
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N
Lobitz
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G
Gisselmann
H
H
Hatt
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CH
Wetzel
D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary / Q000502:physiology; D011985:Receptors, Serotonin / Q000235:genetics* / Q000378:metabolism*; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics* / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D013329:Structure-Activity Relationship
D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012701:Serotonin