title: The HOOK region of voltage-gated Ca2+ channel β subunits senses and transmits PIP2 signals to the gate.
abstract: The β subunit of voltage-gated Ca2+(CaV) channels plays an important role in regulating gating of the α1 pore-forming subunit and its regulation by phosphatidylinositol 4,5-bisphosphate (PIP2). Subcellular localization of the CaVβ subunit is critical for this effect; N-terminal-dependent membrane targeting of the β subunit slows inactivation and decreases PIP2sensitivity. Here, we provide evidence that the HOOK region of the β subunit plays an important role in the regulation of CaVbiophysics. Based on amino acid composition, we broadly divide the HOOK region into three domains: S (polyserine), A (polyacidic), and B (polybasic). We show that a β subunit containing only its A domain in the HOOK region increases inactivation kinetics and channel inhibition by PIP2depletion, whereas a β subunit with only a B domain decreases these responses. When both the A and B domains are deleted, or when the entire HOOK region is deleted, the responses are elevated. Using a peptide-to-liposome binding assay and confocal microscopy, we find that the B domain of the HOOK region directly interacts with anionic phospholipids via polybasic and two hydrophobic Phe residues. The β2c-short subunit, which lacks an A domain and contains fewer basic amino acids and no Phe residues in the B domain, neither associates with phospholipids nor affects channel gating dynamically. Together, our data suggest that the flexible HOOK region of the β subunit acts as an important regulator of CaVchannel gating via dynamic electrostatic and hydrophobic interaction with the plasma membrane.
authors.affiliation: Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea.
authors.forename: Cheon-Gyu
authors.identifier: http://orcid.org/0000-0002-4739-1913
authors.initials: CG
authors.lastname: Park
authors.affiliation: Izmir International Biomedicine and Genome Institute (iBG-izmir), Dokuz Eylul University, 35340 Balcova, Izmir, Turkey.
authors.forename: Yongsoo
authors.initials: Y
authors.lastname: Park
authors.affiliation: Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea bcsuh@dgist.ac.kr.
authors.forename: Byung-Chang
authors.initials: BC
authors.lastname: Suh
mesh_terms: D000818:Animals; D001665:Binding Sites; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D051379:Mice; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D051381:Rats
chemical_list: C503279:Cacna1b protein, rat; D020864:Calcium Channels, N-Type; D019269:Phosphatidylinositol 4,5-Diphosphate; D021122:Protein Subunits