title: Voltage-gated calcium channels of Paramecium cilia.
abstract: Paramecium cells swim by beating their cilia, and make turns by transiently reversing their power stroke. Reversal is caused by Ca2+entering the cilium through voltage-gated Ca2+(CaV) channels that are found exclusively in the cilia. As ciliary Ca2+levels return to normal, the cell pivots and swims forward in a new direction. Thus, the activation of the CaVchannels causes cells to make a turn in their swimming paths. For 45 years, the physiological characteristics of the Paramecium ciliary CaVchannels have been known, but the proteins were not identified until recently, when the P. tetraurelia ciliary membrane proteome was determined. Three CaVα1 subunits that were identified among the proteins were cloned and confirmed to be expressed in the cilia. We demonstrate using RNA interference that these channels function as the ciliary CaVchannels that are responsible for the reversal of ciliary beating. Furthermore, we show that Pawn (pw) mutants of Paramecium that cannot swim backward for lack of CaVchannel activity do not express any of the three CaV1 channels in their ciliary membrane, until they are rescued from the mutant phenotype by expression of the wild-type PW gene. These results reinforce the correlation of the three CaVchannels with backward swimming through ciliary reversal. The PwB protein, found in endoplasmic reticulum fractions, co-immunoprecipitates with the CaV1c channel and perhaps functions in trafficking. The PwA protein does not appear to have an interaction with the channel proteins but affects their appearance in the cilia.
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Sukanya
authors.initials: S
authors.lastname: Lodh
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA Junji.Yano@uvm.edu.
authors.forename: Junji
authors.identifier: 0000-0001-6600-3624
authors.initials: J
authors.lastname: Yano
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Megan S
authors.initials: MS
authors.lastname: Valentine
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Judith L
authors.initials: JL
authors.lastname: Van Houten
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism*; D016384:Consensus Sequence; D047468:Immunoprecipitation; D009154:Mutation / Q000235:genetics; D010247:Paramecium / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D000072417:Protein Domains; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D016622:Silver Staining; D012996:Solutions; D013347:Subcellular Fractions / Q000378:metabolism; D013550:Swimming
chemical_list: D015220:Calcium Channels; D021122:Protein Subunits; D012333:RNA, Messenger; D012996:Solutions
keywords: CaVα1; Cilia; Paramecium; Pawn genes; Trafficking; Voltage-gated calcium channel