Functional characterization of two 5-HT3 receptor splice variants isolated from a mouse hippocampal cell line.
Two splice variants of the ligand-gated 5-hydroxytryptamine or serotonin 5-HT3 receptor that differ in a six-amino-acid deletion were cloned by polymerase chain reaction from the hippocampus x neuroblastoma cell line HN9.10e. When expressed in Xenopus oocytes, both variants individually formed 5-HT3 receptors that revealed no significant differences in current responses to the agonists 5-HT and 1-phenylbiguanide and block by the specific antagonist LY-278, 584-maleate. For both receptors, the monovalent cations Na+, K+, Rb+ and Li+ showed the same relative permeability; NH4(+)permeated approximately 2.7 times better than Na+, and Tris+ was only poorly permeable. In contrast to other reports, the receptors were completely and reversibly blocked by extracellular Cs+ in both oocytes and native HN9.10 cells. Moreover, Ca2+ was not permeant and exhibited a concentration-dependent decrease (0.9-18 mM) of the 5-HT-induced currents without affecting the inward rectification of the current/voltage relation. The two receptors were reversibly inhibited by nanomolar concentrations of the specific inhibitor of protein kinase C (PKC) bisindolylmaleimide, but not by the equipotent and less specific inhibitor staurosporine. A regulatory effect on both 5-HT3 receptor subunits by PKC-mediated protein phosphorylation might be possible, however, a functional role of the two splice variants present in one cell remains to be determined.
Glitsch
M
M
Max-Planck-Institute for Biophysical Chemistry, Molecular Neurobiology of Signal Transduction, Am Fassberg 11, D-37077 Göttingen, Germany.
Wischmeyer
E
E
Karschin
A
A
D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000494:pharmacology; D003001:Cloning, Molecular; D004274:DNA, Recombinant; D004789:Enzyme Activation; D014644:Genetic Variation; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007267:Injections; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D018075:RNA, Complementary; D011985:Receptors, Serotonin / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins; D012701:Serotonin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004274:DNA, Recombinant; D007473:Ion Channels; D015345:Oligonucleotide Probes; D047428:Protein Kinase Inhibitors; D018075:RNA, Complementary; D011985:Receptors, Serotonin; D011994:Recombinant Proteins; D012701:Serotonin; D011494:Protein Kinases; D002118:Calcium