title: The sigma-1 receptor binds to the Nav1.5 voltage-gated Na+ channel with 4-fold symmetry.
abstract: The sigma-1 receptor (Sig1R) is up-regulated in many human tumors and plays a role in the control of cancer cell proliferation and invasiveness. At the molecular level, the Sig1R modulates the activity of various ion channels, apparently through a direct interaction. We have previously shown using atomic force microscopy imaging that the Sig1R binds to the trimeric acid-sensing ion channel 1A with 3-fold symmetry. Here, we investigated the interaction between the Sig1R and the Nav1.5 voltage-gated Na(+) channel, which has also been implicated in promoting the invasiveness of cancer cells. We show that the Sig1R and Nav1.5 can be co-isolated from co-transfected cells, consistent with an intimate association between the two proteins. Atomic force microscopy imaging of the co-isolated proteins revealed complexes in which Nav1.5 was decorated by Sig1Rs. Frequency distributions of angles between pairs of bound Sig1Rs had two peaks, at ∼90° and ∼180°, and the 90° peak was about twice the size of the 180° peak. These results demonstrate that the Sig1R binds to Nav1.5 with 4-fold symmetry. Hence, each set of six transmembrane regions in Nav1.5 likely constitutes a Sig1R binding site, suggesting that the Sig1R interacts with the transmembrane regions of its partners. Interestingly, two known Sig1R ligands, haloperidol and (+)-pentazocine, disrupted the Nav1.5/Sig1R interaction both in vitro and in living cells. Finally, we show that endogenously expressed Sig1R and Nav1.5 also functionally interact.
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
authors.forename: Dilshan
authors.initials: D
authors.lastname: Balasuriya
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Stewart
authors.forename: David
authors.initials: D
authors.lastname: Crottès
authors.forename: Franck
authors.initials: F
authors.lastname: Borgese
authors.forename: Olivier
authors.initials: O
authors.lastname: Soriani
authors.forename: J Michael
authors.initials: JM
authors.lastname: Edwardson
mesh_terms: D002460:Cell Line; D002846:Chromatography, Affinity; D055785:Gene Knockdown Techniques; D006220:Haloperidol / Q000737:chemistry; D006801:Humans; D008024:Ligands; D008564:Membrane Potentials; D018625:Microscopy, Atomic Force; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010423:Pentazocine / Q000737:chemistry; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D034622:RNA Interference; D017480:Receptors, sigma / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D059010:Single-Cell Analysis; D000097605:Sigma-1 Receptor
chemical_list: D006220:Haloperidol; D008024:Ligands; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010423:Pentazocine; D017480:Receptors, sigma; D000097605:Sigma-1 Receptor; C568320:SCN5A protein, human