title: Axonal targeting of Caspr2 in hippocampal neurons via selective somatodendritic endocytosis.
abstract: Contactin-associated protein 2 (Caspr2) is a neuronal membrane protein that is mutated in autism and related disorders. Although it is highly enriched at juxtaparanodes of Ranvier where it is essential for Shaker-type K(+) channel clustering, little is known about its function and regulation. In the present study, we examined the polarized expression of Caspr2 in hippocampal neurons using extracellular hemagglutinin (HA)-tagged Caspr2 constructs. We found that Caspr2 was targeted to the axonal surface, but colocalized with early endosomes in the somatodendritic compartment. The inhibition of endocytosis using a Dynamin-1 mutant or treatment with Dynasore prevented Caspr2 internalization from the dendrites and cell body. We identified a short sequence included into the 4.1B-binding domain that is required for the endocytosis of Caspr2. This sequence contains a protein kinase C (PKC) substrate motif on Thr1292, and point mutation of this residue or treatment with a PKC inhibitor prevented the somatodendritic internalization of Caspr2. Thus, the PKC-dependent trafficking of Caspr2 underlies its polarized expression in hippocampal neurons.
authors.affiliation: Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, UMR 6231 CNRS, Université de la Méditerranée Aix-Marseille II, Marseille 13916, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Bel
authors.forename: Ksénia
authors.initials: K
authors.lastname: Oguievetskaia
authors.forename: Christophe
authors.initials: C
authors.lastname: Pitaval
authors.forename: Laurence
authors.initials: L
authors.lastname: Goutebroze
authors.forename: Catherine
authors.initials: C
authors.lastname: Faivre-Sarrailh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism*; D019556:COS Cells; D002451:Cell Compartmentation; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism*; D004705:Endocytosis; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D015398:Signal Transduction
chemical_list: C403049:CNTNAP2 protein, human; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011493:Protein Kinase C