title: Calcium currents are enhanced by α2δ-1 lacking its membrane anchor.
abstract: The accessory α(2)δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α(2) and δ. All α(2)δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α(2)δ subunits, we have now examined the properties of α(2)δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α(2)δ-1ΔC-term). We find that the majority of α(2)δ-1ΔC-term is soluble and secreted into the medium, but unexpectedly, some of the protein remains associated with detergent-resistant membranes, also termed lipid rafts, and is extrinsically bound to the plasma membrane. Furthermore, heterologous co-expression of α(2)δ-1ΔC-term with Ca(V)2.1/β1b results in a substantial enhancement of the calcium channel currents, albeit less than that produced by wild-type α(2)δ-1. These results call into question the role of membrane anchoring of α(2)δ subunits for calcium current enhancement.
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom. i.kadurin@ucl.ac.uk
authors.forename: Ivan
authors.initials: I
authors.lastname: Kadurin
authors.forename: Anita
authors.initials: A
authors.lastname: Alvarez-Laviada
authors.forename: Shu Fun Josephine
authors.initials: SF
authors.lastname: Ng
authors.forename: Ryan
authors.initials: R
authors.lastname: Walker-Gray
authors.forename: Marianna
authors.initials: M
authors.lastname: D'Arco
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fadel
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Pratt
authors.forename: Annette C
authors.initials: AC
authors.lastname: Dolphin
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D005727:Ganglia, Spinal / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry / Q000379:methods; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017422:Sequence Analysis, DNA
chemical_list: D002118:Calcium; D020864:Calcium Channels, N-Type; D018076:DNA, Complementary; D021122:Protein Subunits