Characterization of recombinant and native Ih-channels from Apis mellifera |
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Authors: | Gisselmann Günter Warnstedt Maike Gamerschlag Birgit Bormann Anja Marx Thomas Neuhaus Eva M Stoertkuhl Klemens Wetzel Christian H Hatt Hanns |
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Institution: | 1. Fakultät für Biologie, Lehrstuhl für Zellphysiologie ND4, Ruhr-Universität-Bochum, Universitätsstr. 150, 44780 Bochum, Germany;2. Fakultät für Chemie, Molekulare Zellbiochemie, Ruhr-Universität-Bochum, Universitätsstr. 150, 44780 Bochum, Germany;1. College of Chemistry & Chemical Engineering, Binzhou University, Binzhou 256603, PR China;2. Department of Physics, National University of Singapore, 117542, Singapore;1. Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi''an 710038, PR China;2. Key Laboratory of Brain Stress and Behavior, PLA, Xi''an 710038, PR China;3. Beijing Institute for Brain Disorders, Beijing 100069, PR China;4. Department of Psychology, College of Science, The University of Texas at Arlington, Arlington, TX 76019, USA;1. Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, SLP 78210, Mexico;2. Facultad de Ingeniería, Universidad Autónoma de Baja California, Mexicali, BC, 21280, Mexico |
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Abstract: | Recently, a novel class of genes coding for Ih-channels has been identified in several vertebrates and invertebrates. We isolated a cDNA (AMIH) encoding a putative member of these ion channels from Apis mellifera heads by means of polymerase chain reaction and homology screening. High similarity (88% identical amino acids) to the putative Drosophila melanogaster Ih-channel suggests that the Apis cDNA codes for a hyperpolarization-activated and cyclic nucleotide-gated channel. Functional expression of recombinant AMIH in HEK293 cells gave unitary currents that were preferentially selective for potassium over sodium ions and were activated by hyperpolarizing voltage steps. Cyclic nucleotides shifted the voltage activation curve to more positive membrane potentials. The current kinetics, activation by hyperpolarizing voltage steps and modulatory influence of cyclic nucleotides properties closely resemble those of mammalian Ih-channels. RT-PCR analysis showed pronounced mRNA expression in the antennae, head and body of Apis mellifera. Investigation of hyperpolarization-activated currents in olfactory receptor neurons (ORNs) in a primary cell culture of Apis mellifera antennal cells revealed activation properties similar to the heterologously expressed Ih-channel. By in-situ hybridization and immunohistochemistry, expression of AMIH was seen in olfactory receptor neurons of the bee antennae. We conclude that AMIH is the ion channel responsible for the hyperpolarization-activated currents in olfactory receptor neurons of bee. |
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