title: CK2-regulated schwannomin-interacting protein IQCJ-SCHIP-1 association with AnkG contributes to the maintenance of the axon initial segment.
abstract: The axon initial segment (AIS) plays a central role in electrogenesis and in the maintenance of neuronal polarity. Its molecular organization is dependent on the scaffolding protein ankyrin (Ank) G and is regulated by kinases. For example, the phosphorylation of voltage-gated sodium channels by the protein kinase CK2 regulates their interaction with AnkG and, consequently, their accumulation at the AIS. We previously showed that IQ motif containing J-Schwannomin-Interacting Protein 1 (IQCJ-SCHIP-1), an isoform of the SCHIP-1, accumulated at the AIS in vivo. Here, we analyzed the molecular mechanisms involved in IQCJ-SCHIP-1-specific axonal location. We showed that IQCJ-SCHIP-1 accumulation in the AIS of cultured hippocampal neurons depended on AnkG expression. Pull-down assays and surface plasmon resonance analysis demonstrated that AnkG binds to CK2-phosphorylated IQCJ-SCHIP-1 but not to the non-phosphorylated protein. Surface plasmon resonance approaches using IQCJ-SCHIP-1, SCHIP-1a, another SCHIP-1 isoform, and their C-terminus tail mutants revealed that a segment including multiple CK2-phosphorylatable sites was directly involved in the interaction with AnkG. Pharmacological inhibition of CK2 diminished both IQCJ-SCHIP-1 and AnkG accumulation in the AIS. Silencing SCHIP-1 expression reduced AnkG cluster at the AIS. Finally, over-expression of IQCJ-SCHIP-1 decreased AnkG concentration at the AIS, whereas a mutant deleted of the CK2-regulated AnkG interaction site did not. Our study reveals that CK2-regulated IQJC-SCHIP-1 association with AnkG contributes to AIS maintenance. The axon initial segment (AIS) organization depends on ankyrin (Ank) G and kinases. Here we showed that AnkG binds to CK2-phosphorylated IQCJ-SCHIP-1, in a segment including 12 CK2-phosphorylatable sites. In cultured neurons, either pharmacological inhibition of CK2 or IQCJ-SCHIP-1 silencing reduced AnkG clustering. Overexpressed IQCJ-SCHIP-1 decreased AnkG concentration at the AIS whereas a mutant deleted of the CK2-regulated AnkG interaction site did not. Thus, CK2-regulated IQJC-SCHIP-1 association with AnkG contributes to AIS maintenance.
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Marie-Jeanne
authors.initials: MJ
authors.lastname: Papandréou
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Vacher
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Fache
authors.affiliation: Institut du Fer à Moulin, Inserm, UMR-S 839, Université Pierre et Marie-Curie, Paris, France.
authors.forename: Esther
authors.initials: E
authors.lastname: Klingler
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Fanny
authors.initials: F
authors.lastname: Rueda-Boroni
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Ferracci
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Debarnot
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Pipéroglou
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.|Department of Neurosciences, University of the Basque Country, Vitoria-Gasteiz, Spain.
authors.forename: Gontzal
authors.initials: G
authors.lastname: Garcia Del Caño
authors.affiliation: Institut du Fer à Moulin, Inserm, UMR-S 839, Université Pierre et Marie-Curie, Paris, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Goutebroze
authors.affiliation: CRN2M-UMR7286, Aix Marseille Université, CNRS, Marseille, France.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Dargent
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D001369:Axons / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D047390:Casein Kinase II / Q000378:metabolism*; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D006624:Hippocampus / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D051381:Rats; D017208:Rats, Wistar; D020349:Surface Plasmon Resonance; D014162:Transfection
chemical_list: D017487:Ankyrins; D002352:Carrier Proteins; C000600131:SCHIP1 protein, mouse; D047390:Casein Kinase II
keywords: SCHIP-1; ankyrin G; axon initial segment; protein kinase CK2