title: Molecular characterization of a neuronal-specific protein that stimulates the activity of Cdk5.
abstract: Cyclin-dependent kinase, Cdk5, has been identified in neural tissue in connection with neurofilament and tau protein phosphorylation. This report describes the characterization of a 62-kDa protein that copurifies with Cdk5 from rat spinal cord homogenates. Dissociation of the protein from neural Cdk5 is concomitant with a reversible loss in kinase activity. Amino acid sequence information from tryptic peptide fragments was used to clone the complementary DNA from rat brain. A single full-length cDNA was characterized coding for a 67.5-kDa protein (p67). Exogenously expressed p67 stimulated Cdk5 kinase activity in vitro in a dose-dependent manner and when presented as an affinity matrix, selectively adsorbed Cdk5 from a cleared rat brain homogenate. In situ hybridization analysis of E18 rat embryos and adult rat brain demonstrated that p67 transcript expression is restricted to neural tissue. Immunohistochemical staining with an amino-terminal peptide-specific antibody further indicated that p67 is exclusively expressed in neurons. Localization in vivo and in cultured rat hippocampal neurons showed that p67 is highly enriched in axons. We propose that p67, by virtue of its regulation of Cdk5, participates in the dynamics of axonal architecture through the modulation of phosphorylation of cytoskeletal components.
authors.affiliation: Laboratory of Neurochemistry, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-4062, USA.
authors.forename: K T
authors.initials: KT
authors.lastname: Shetty
authors.forename: S
authors.initials: S
authors.lastname: Kaech
authors.forename: W T
authors.initials: WT
authors.lastname: Link
authors.forename: H
authors.initials: H
authors.lastname: Jaffe
authors.forename: C M
authors.initials: CM
authors.lastname: Flores
authors.forename: S
authors.initials: S
authors.lastname: Wray
authors.forename: H C
authors.initials: HC
authors.lastname: Pant
authors.forename: S
authors.initials: S
authors.lastname: Beushausen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology; D009474:Neurons / Q000201:enzymology*; D010446:Peptide Fragments / Q000737:chemistry; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D012194:RNA-Directed DNA Polymerase; D051381:Rats; D013116:Spinal Cord / Q000201:enzymology; D014018:Tissue Distribution; D033921:Vesicular Transport Proteins
chemical_list: D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; D033921:Vesicular Transport Proteins; D051360:Cyclin-Dependent Kinase 5; D017346:Protein Serine-Threonine Kinases; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases; D012194:RNA-Directed DNA Polymerase