title: Regulation of synaptojanin 1 by cyclin-dependent kinase 5 at synapses.
abstract: Synaptojanin 1 is a polyphosphoinositide phosphatase concentrated in presynaptic nerve terminals, where it dephosphorylates a pool of phosphatidylinositol 4,5-bisphosphate implicated in synaptic vesicle recycling. Like other proteins with a role in endocytosis, synaptojanin 1 undergoes constitutive phosphorylation in resting synapses and stimulation-dependent dephosphorylation by calcineurin. Here, we show that cyclin-dependent kinase 5 (Cdk5) phosphorylates synaptojanin 1 and regulates its function both in vitro and in intact synaptosomes. Cdk5 phosphorylation inhibited the inositol 5-phosphatase activity of synaptojanin 1, whereas dephosphorylation by calcineurin stimulated such activity. The activity of synaptojanin 1 was also stimulated by its interaction with endophilin 1, its major binding partner at the synapse. Notably, Cdk5 phosphorylated serine 1144, which is adjacent to the endophilin binding site. Mutation of serine 1144 to aspartic acid to mimic phosphorylation by Cdk5 inhibited the interaction of synaptojanin 1 with endophilin 1. These results suggest that Cdk5 and calcineurin may have an antagonistic role in the regulation of synaptojanin 1 recruitment and activity, and therefore in the regulation of phosphatidylinositol 4,5-bisphosphate turnover at synapses.
authors.affiliation: Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06510, USA.
authors.forename: Sang Yoon
authors.initials: SY
authors.lastname: Lee
authors.forename: Markus R
authors.initials: MR
authors.lastname: Wenk
authors.forename: Yong
authors.initials: Y
authors.lastname: Kim
authors.forename: Angus C
authors.initials: AC
authors.lastname: Nairn
authors.forename: Pietro
authors.initials: P
authors.lastname: De Camilli
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D019703:Calcineurin / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000502:physiology*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000502:physiology*; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology*; D010766:Phosphorylation; D051381:Rats; D012694:Serine / Q000378:metabolism; D013569:Synapses / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D009419:Nerve Tissue Proteins; C075637:amphiphysin; D012694:Serine; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases; C097702:synaptojanin; D019703:Calcineurin; D010744:Phosphoric Monoester Hydrolases