title: Auxiliary subunit regulation of high-voltage activated calcium channels expressed in mammalian cells.
abstract: The effects of auxiliary calcium channel subunits on the expression and functional properties of high-voltage activated (HVA) calcium channels have been studied extensively in the Xenopus oocyte expression system, but are less completely characterized in a mammalian cellular environment. Here, we provide the first systematic analysis of the effects of calcium channel beta and alpha(2)-delta subunits on expression levels and biophysical properties of three different types (Ca(v)1.2, Ca(v)2.1 and Ca(v)2.3) of HVA calcium channels expressed in tsA-201 cells. Our data show that Ca(v)1.2 and Ca(v)2.3 channels yield significant barium current in the absence of any auxiliary subunits. Although calcium channel beta subunits were in principle capable of increasing whole cell conductance, this effect was dependent on the type of calcium channel alpha(1) subunit, and beta(3) subunits altogether failed to enhance current amplitude irrespective of channel subtype. Moreover, the alpha(2)-delta subunit alone is capable of increasing current amplitude of each channel type examined, and at least for members of the Ca(v)2 channel family, appears to act synergistically with beta subunits. In general agreement with previous studies, channel activation and inactivation gating was regulated both by beta and by alpha(2)-delta subunits. However, whereas pronounced regulation of inactivation characteristics was seen with the majority of the auxiliary subunits, effects on voltage dependence of activation were only small (< 5 mV). Overall, through a systematic approach, we have elucidated a previously underestimated role of the alpha(2)-delta(1) subunit with regard to current enhancement and kinetics. Moreover, the effects of each auxiliary subunit on whole cell conductance and channel gating appear to be specifically tailored to subsets of calcium channel subtypes.
authors.affiliation: Department of Physiology and Biophysics, Cellular and Molecular Neurobiology Research Group, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4 N1, Canada.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yasuda
authors.forename: Lina
authors.initials: L
authors.lastname: Chen
authors.forename: Wendy
authors.initials: W
authors.lastname: Barr
authors.forename: John E
authors.initials: JE
authors.lastname: McRory
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lewis
authors.forename: David J
authors.initials: DJ
authors.lastname: Adams
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004553:Electric Conductivity; D004622:Embryo, Mammalian; D015870:Gene Expression / Q000502:physiology*; D049452:Green Fluorescent Proteins; D006801:Humans; D015640:Ion Channel Gating; D007668:Kidney; D008164:Luminescent Proteins / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014162:Transfection / Q000379:methods
chemical_list: D015220:Calcium Channels; D008164:Luminescent Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins