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Mallmann R, Ondacova K, Moravcikova L, Jurkovicova-Tarabova B, Pavlovicova M, Moravcik R, Lichvarova L, Kominkova V, Klugbauer N, Lacinova L. Four novel interaction partners demonstrate diverse modulatory effects on voltage-gated Ca V2.2 Ca 2+ channels. Pflugers Arch 2019; 471:861-874. [PMID: 30612149 DOI: 10.1007/s00424-018-02248-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 12/14/2018] [Accepted: 12/18/2018] [Indexed: 12/11/2022]
Abstract
Voltage-gated Ca2+ channels are embedded in a network of protein interactions that are fundamental for channel function and modulation. Different strategies such as high-resolution quantitative MS analyses and yeast-two hybrid screens have been used to uncover these Ca2+ channel nanodomains. We applied the yeast split-ubiquitin system with its specific advantages to search for interaction partners of the CaV2.2 Ca2+ channel and identified four proteins: reticulon 1 (RTN1), member 1 of solute carrier family 38 (SLC38), prostaglandin D2 synthase (PTGDS) and transmembrane protein 223 (TMEM223). Interactions were verified using the yeast split-ubiquitin system and narrowed down to CaV2.2 domain IV. Colocalization studies using fluorescent constructs demonstrated defined regions of subcellular localization. Detailed electrophysiological studies revealed that coexpression of RTN1 modulated CaV2.2 channels only to a minor extent. SLC38 accelerated the cumulative current inactivation during a high-frequency train of brief depolarizing pulses. As neurons expressing CaV2.2 channels were exposed to high-frequency bursts under physiological conditions, observed regulation may have a negative modulatory effect on transmitter release. Coexpression of PTGDS significantly lowered the average current density and slowed the kinetics of cumulative current inactivation. Since the latter effect was not significant, it may only partly compensate the first one under physiological conditions. Expression of TMEM223 lowered the average current density, accelerated the kinetics of cumulative current inactivation and slowed the kinetics of recovery from inactivation. Therefore, TMEM223 and, to a lesser extent, PTGDS, may negatively modulate Ca2+ entry required for transmitter release and/or for dendritic plasticity under physiological conditions.
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Affiliation(s)
- Robert Mallmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Fakultät für Medizin, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Katarina Ondacova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | - Lucia Moravcikova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | | | - Michaela Pavlovicova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | - Roman Moravcik
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | - Lucia Lichvarova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | - Viera Kominkova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia
| | - Norbert Klugbauer
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Fakultät für Medizin, Albert-Ludwigs-Universität Freiburg, Albertstr. 25, 79104, Freiburg, Germany
| | - Lubica Lacinova
- Center of Bioscience, Institute for Molecular Physiology and Genetics, 84005, Bratislava, Slovakia.
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Kim DI, Kweon HJ, Park Y, Jang DJ, Suh BC. Ca2+ controls gating of voltage-gated calcium channels by releasing the β2e subunit from the plasma membrane. Sci Signal 2016; 9:ra67. [PMID: 27382026 DOI: 10.1126/scisignal.aad7247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Voltage-gated calcium (Cav) channels, which are regulated by membrane potential, cytosolic Ca(2+), phosphorylation, and membrane phospholipids, govern Ca(2+) entry into excitable cells. Cav channels contain a pore-forming α1 subunit, an auxiliary α2δ subunit, and a regulatory β subunit, each encoded by several genes in mammals. In addition to a domain that interacts with the α1 subunit, β2e and β2a also interact with the cytoplasmic face of the plasma membrane through an electrostatic interaction for β2e and posttranslational acylation for β2a. We found that an increase in cytosolic Ca(2+) promoted the release of β2e from the membrane without requiring substantial depletion of the anionic phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) from the plasma membrane. Experiments with liposomes indicated that Ca(2+) disrupted the interaction of the β2e amino-terminal peptide with membranes containing PIP2 Ca(2+) binding to calmodulin (CaM) leads to CaM-mediated inactivation of Cav currents. Although Cav2.2 coexpressed with β2a required Ca(2+)-dependent activation of CaM for Ca(2+)-mediated reduction in channel activity, Cav2.2 coexpressed with β2e exhibited Ca(2+)-dependent inactivation of the channel even in the presence of Ca(2+)-insensitive CaM. Inducible depletion of PIP2 reduced Cav2.2 currents, and in cells coexpressing β2e, but not a form that lacks the polybasic region, increased intracellular Ca(2+) further reduced Cav2.2 currents. Many hormone- or neurotransmitter-activated receptors stimulate PIP2 hydrolysis and increase cytosolic Ca(2+); thus, our findings suggest that β2e may integrate such receptor-mediated signals to limit Cav activity.
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Affiliation(s)
- Dong-Il Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Hae-Jin Kweon
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Yongsoo Park
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Deok-Jin Jang
- Department of Ecological Science, College of Ecology and Environment, Kyungpook National University, Kyungbuk 742-711, Korea
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea.
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Molecular Basis of the Membrane Interaction of the β2e Subunit of Voltage-Gated Ca(2+) Channels. Biophys J 2016; 109:922-35. [PMID: 26331250 DOI: 10.1016/j.bpj.2015.07.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 07/27/2015] [Accepted: 07/28/2015] [Indexed: 12/30/2022] Open
Abstract
The auxiliary β subunit plays an important role in the regulation of voltage-gated calcium (CaV) channels. Recently, it was revealed that β2e associates with the plasma membrane through an electrostatic interaction between N-terminal basic residues and anionic phospholipids. However, a molecular-level understanding of β-subunit membrane recruitment in structural detail has remained elusive. In this study, using a combination of site-directed mutagenesis, liposome-binding assays, and multiscale molecular-dynamics (MD) simulation, we developed a physical model of how the β2e subunit is recruited electrostatically to the plasma membrane. In a fluorescence resonance energy transfer assay with liposomes, binding of the N-terminal peptide (23 residues) to liposome was significantly increased in the presence of phosphatidylserine (PS) and phosphatidylinositol 4,5-bisphosphate (PIP2). A mutagenesis analysis suggested that two basic residues proximal to Met-1, Lys-2 (K2) and Trp-5 (W5), are more important for membrane binding of the β2e subunit than distal residues from the N-terminus. Our MD simulations revealed that a stretched binding mode of the N-terminus to PS is required for stable membrane attachment through polar and nonpolar interactions. This mode obtained from MD simulations is consistent with experimental results showing that K2A, W5A, and K2A/W5A mutants failed to be targeted to the plasma membrane. We also investigated the effects of a mutated β2e subunit on inactivation kinetics and regulation of CaV channels by PIP2. In experiments with voltage-sensing phosphatase (VSP), a double mutation in the N-terminus of β2e (K2A/W5A) increased the PIP2 sensitivity of CaV2.2 and CaV1.3 channels by ∼3-fold compared with wild-type β2e subunit. Together, our results suggest that membrane targeting of the β2e subunit is initiated from the nonspecific electrostatic insertion of N-terminal K2 and W5 residues into the membrane. The PS-β2e interaction observed here provides a molecular insight into general principles for protein binding to the plasma membrane, as well as the regulatory roles of phospholipids in transporters and ion channels.
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