title: Phosphorylation of microtubule-associated protein STOP by calmodulin kinase II.
abstract: STOP proteins are microtubule-associated, calmodulin-regulated proteins responsible for the high degree of stabilization displayed by neuronal microtubules. STOP suppression in mice induces synaptic defects affecting both short and long term synaptic plasticity in hippocampal neurons. Interestingly, STOP has been identified as a component of synaptic structures in neurons, despite the absence of microtubules in nerve terminals, indicating the existence of mechanisms able to induce a translocation of STOP from microtubules to synaptic compartments. Here we have tested STOP phosphorylation as a candidate mechanism for STOP relocalization. We show that, both in vitro and in vivo, STOP is phosphorylated by the multifunctional enzyme calcium/calmodulin-dependent protein kinase II (CaMKII), which is a key enzyme for synaptic plasticity. This phosphorylation occurs on at least two independent sites. Phosphorylated forms of STOP do not bind microtubules in vitro and do not co-localize with microtubules in cultured differentiating neurons. Instead, phosphorylated STOP co-localizes with actin assemblies along neurites or at branching points. Correlatively, we find that STOP binds to actin in vitro. Finally, in differentiated neurons, phosphorylated STOP co-localizes with clusters of synaptic proteins, whereas unphosphorylated STOP does not. Thus, STOP phosphorylation by CaMKII may promote STOP translocation from microtubules to synaptic compartments where it may interact with actin, which could be important for STOP function in synaptic plasticity.
authors.affiliation: Laboratoire du Cytosquelette, INSERM U366, DRDC/CS, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble cedex 9, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Baratier
authors.forename: Leticia
authors.initials: L
authors.lastname: Peris
authors.forename: Jacques
authors.initials: J
authors.lastname: Brocard
authors.forename: Sylvie
authors.initials: S
authors.lastname: Gory-Fauré
authors.forename: Fabrice
authors.initials: F
authors.lastname: Dufour
authors.forename: Christophe
authors.initials: C
authors.lastname: Bosc
authors.forename: Anne
authors.initials: A
authors.lastname: Fourest-Lieuvin
authors.forename: Laurent
authors.initials: L
authors.lastname: Blanchoin
authors.forename: Paul
authors.initials: P
authors.lastname: Salin
authors.forename: Didier
authors.initials: D
authors.lastname: Job
authors.forename: Annie
authors.initials: A
authors.lastname: Andrieux
mesh_terms: D000199:Actins / Q000737:chemistry; D000818:Animals; D001921:Brain / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D013569:Synapses / Q000378:metabolism
chemical_list: D000199:Actins; D002147:Calmodulin; D008869:Microtubule-Associated Proteins; C491893:Mtap6 protein, mouse; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases