CK2‐regulated schwannomin‐interacting protein IQCJ‐SCHIP‐1 association with AnkG contributes to the maintenance of the axon initial segment

• Published in: Journal of neurochemistry Vol. 134; no. 3; pp. 527 - 537
• Main Authors: Papandréou, Marie‐Jeanne, Vacher, Hélène, Fache, Marie‐Pierre, Klingler, Esther, Rueda‐Boroni, Fanny, Ferracci, Géraldine, Debarnot, Claire, Pipéroglou, Christelle, Del Caño, Gontzal Garcia, Goutebroze, Laurence, Dargent, Bénédicte
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2015; Wiley
• Subjects: Animals; ankyrin G; Ankyrins - metabolism; axon initial segment; Axons - metabolism; Blotting, Western; Carrier Proteins - metabolism; Casein Kinase II - metabolism; Cells, Cultured; Fluorescent Antibody Technique; Hippocampus - metabolism; Life Sciences; Mice; Microscopy, Confocal; Molecular Sequence Data; Neurobiology; Neurochemistry; Neurons and Cognition; protein kinase CK2; Proteins; Rats; Rats, Wistar; SCHIP‐1; Surface Plasmon Resonance; Transfection; protein kinase CK2; SCHIP-1; axon initial segment; ankyrin G
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/jnc.13158

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. 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.