The α 2 δ subunits of voltage-gated calcium channels form GPI-anchored proteins, a posttranslational modification essential for function
Open Access
- 4 January 2010
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 107 (4), 1654-1659
- https://doi.org/10.1073/pnas.0908735107
Abstract
Voltage-gated calcium channels are thought to exist in the plasma membrane as heteromeric proteins, in which the α1 subunit is associated with two auxiliary subunits, the intracellular β subunit and the α2δ subunit; both of these subunits influence the trafficking and properties of CaV1 and CaV2 channels. The α2δ subunits have been described as type I transmembrane proteins, because they have an N-terminal signal peptide and a C-terminal hydrophobic and potentially transmembrane region. However, because they have very short C-terminal cytoplasmic domains, we hypothesized that the α2δ proteins might be associated with the plasma membrane through a glycosylphosphatidylinositol (GPI) anchor attached to δ rather than a transmembrane domain. Here, we provide biochemical, immunocytochemical, and mutational evidence to show that all of the α2δ subunits studied, α2δ-1, α2δ-2, and α2δ-3, show all of the properties expected of GPI-anchored proteins, both when heterologously expressed and in native tissues. They are substrates for prokaryotic phosphatidylinositol-phospholipase C (PI-PLC) and trypanosomal GPI-PLC, which release the α2δ proteins from membranes and intact cells and expose a cross-reacting determinant epitope. PI-PLC does not affect control transmembrane or membrane-associated proteins. Furthermore, mutation of the predicted GPI-anchor sites markedly reduced plasma membrane and detergent-resistant membrane localization of α2δ subunits. We also show that GPI anchoring of α2δ subunits is necessary for their function to enhance calcium currents, and PI-PLC treatment only reduces calcium current density when α2δ subunits are coexpressed. In conclusion, this study redefines our understanding of α2δ subunits, both in terms of their role in calcium-channel function and other roles in synaptogenesis.Keywords
This publication has 33 references indexed in Scilit:
- Presynaptic α2δ-3 is required for synaptic morphogenesis independent of its Ca2+-channel functionsNature Neuroscience, 2009
- Gabapentin Receptor α2δ-1 Is a Neuronal Thrombospondin Receptor Responsible for Excitatory CNS SynaptogenesisCell, 2009
- Characterization of the glycosylphosphatidylinositol-anchor signal sequence of human Cryptic with a hydrophilic extensionBiochimica et Biophysica Acta (BBA) - Biomembranes, 2008
- Structural changes of membrane-anchored native PrP CProceedings of the National Academy of Sciences, 2008
- Immunostaining of rat brain, spinal cord, sensory neurons and skeletal muscle for calcium channel alpha2-delta (α2-δ) type 1 proteinNeuroscience, 2008
- Pharmacological disruption of calcium channel trafficking by the α 2 δ ligand gabapentinProceedings of the National Academy of Sciences of the United States of America, 2008
- Functional biology of the α2δ subunits of voltage-gated calcium channelsTrends in Pharmacological Sciences, 2007
- Kinetics of internalization and degradation of N-type voltage-gated calcium channels: Role of the α2/δ subunitCell Calcium, 2007
- Identification of the α 2 -δ-1 subunit of voltage-dependent calcium channels as a molecular target for pain mediating the analgesic actions of pregabalinProceedings of the National Academy of Sciences of the United States of America, 2006
- Use of site‐directed antibodies to probe the topography of theα2 subunit of voltage‐gated Ca2+ channelsFEBS Letters, 1995