title: Cyclin-dependent kinase 5 activators p35 and p39 facilitate formation of functional synapses.
abstract: Cyclin-dependent kinase 5 (Cdk5) has emerged as a key coordinator of cell signaling in neurite outgrowth. Cdk5 needs to associate with one of the regulatory proteins p35 or p39 to be an active enzyme. To investigate if Cdk5 plays a role in the establishment of functional synapses, we have characterized the expression of Cdk5, p35, and p39 in the neuroblastoma-glioma cell line NG108-15, and recorded postsynaptic activity in myotubes in response to presynaptic overexpression of Cdk5, p35, and p39. Endogenous Cdk5 and p35 protein levels increased with cellular differentiation and preferentially distributed to soluble pools, whereas the level of p39 protein remained low and primarily was present in membrane and cytoskeletal fractions. Transient transfection of a dominant-negative mutant of Cdk5 in NG108-15 cells and subsequent culturing on differentiating muscle cells resulted in a significant reduction in synaptic activity, as measured by postsynaptic miniature endplate potentials (mEPPs). Overexpression of either Cdk5/p35 or Cdk5/p39 resulted in a substantial increase in synaptic structures that displayed postsynaptic activities, as well as mEPP frequency. These findings demonstrate that Cdk5, p35, and p39 are endogenously expressed in NG108-15 cells, exhibit distinct subcellular localizations, and that both Cdk5/p35 and Cdk5/p39 are central in formation of functional synapses.
authors.affiliation: Department of Molecular Medicine, The Rolf Luft Center for Diabetes Research, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden.
authors.forename: Jenny U
authors.initials: JU
authors.lastname: Johansson
authors.forename: Lena
authors.initials: L
authors.lastname: Lilja
authors.forename: Xiao-Liang
authors.initials: XL
authors.lastname: Chen
authors.forename: Haruhiro
authors.initials: H
authors.lastname: Higashida
authors.forename: Björn
authors.initials: B
authors.lastname: Meister
authors.forename: Mami
authors.initials: M
authors.lastname: Noda
authors.forename: Zhen-Guo
authors.initials: ZG
authors.lastname: Zhong
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Berggren
authors.forename: Christina
authors.initials: C
authors.lastname: Bark
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D002490:Central Nervous System / Q000196:embryology / Q000201:enzymology*; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000201:enzymology; D004789:Enzyme Activation / Q000502:physiology; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009434:Neural Pathways / Q000196:embryology / Q000201:enzymology*; D009469:Neuromuscular Junction / Q000196:embryology / Q000201:enzymology; D051381:Rats; D013569:Synapses / Q000201:enzymology*; D009435:Synaptic Transmission / Q000235:genetics; D015854:Up-Regulation / Q000502:physiology
chemical_list: C108298:Cdk5 activator p39; D009419:Nerve Tissue Proteins; C089495:neuronal Cdk5 activator (p25-p35); D051360:Cyclin-Dependent Kinase 5; C495906:Cdk5 protein, mouse; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases