title: Cdk5/p35 regulates neurotransmitter release through phosphorylation and downregulation of P/Q-type voltage-dependent calcium channel activity.
abstract: Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase with close structural homology to the mitotic Cdks. The complex of Cdk5 and p35, the neuron-specific regulatory subunit of Cdk5, plays important roles in brain development, such as neuronal migration and neurite outgrowth. Moreover, Cdk5 is thought to be involved in the promotion of neurodegeneration in Alzheimer's disease. Cdk5 is abundant in mature neurons; however, its physiological functions in the adult brain are unknown. Here we show that Cdk5/p35 regulates neurotransmitter release in the presynaptic terminal. Both Cdk5 and p35 were abundant in the synaptosomes. Roscovitine, a specific inhibitor of Cdk5 in neurons, induced neurotransmitter release from the synaptosomes in response to membrane depolarization and enhanced the EPSP slopes in rat hippocampal slices. The electrophysiological study using each specific inhibitor of the voltage-dependent calcium channels (VDCCs) and calcium imaging revealed that roscovitine enhanced Ca2+ influx from the P/Q-type VDCC. Moreover, Cdk5/p25 phosphorylated the intracellular loop connecting domains II and III (L(II-III)) between amino acid residues 724 and 981 of isoforms cloned from rat brain of the alpha1A subunit of P/Q-type Ca2+ channels. The phosphorylation inhibited the interaction of L(II-III) with SNAP-25 and synaptotagmin I, which were plasma membrane soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) proteins and were required for efficient neurotransmitter release. These results strongly suggest that Cdk5/p35 inhibits neurotransmitter release through the phosphorylation of P/Q-type VDCC and downregulation of the channel activity.
authors.affiliation: Department of Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan. tomikt@md.okayama-u.ac.jp
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Tomizawa
authors.forename: Jun
authors.initials: J
authors.lastname: Ohta
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsushita
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Moriwaki
authors.forename: Sheng-Tian
authors.initials: ST
authors.lastname: Li
authors.forename: Kohji
authors.initials: K
authors.lastname: Takei
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsui
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020865:Calcium Channels, P-Type / Q000378:metabolism*; D020907:Calcium Channels, Q-Type / Q000378:metabolism*; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015536:Down-Regulation; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D066298:In Vitro Techniques; D007701:Kinetin; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D000077546:Roscovitine; D013574:Synaptosomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D004791:Enzyme Inhibitors; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D020033:Protein Isoforms; D011687:Purines; C089495:neuronal Cdk5 activator (p25-p35); D000077546:Roscovitine; D018698:Glutamic Acid; C090046:olomoucine; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat; D018844:Cyclin-Dependent Kinases; D007701:Kinetin; D002118:Calcium