CDK5P25 Recombinant Protein

The protein encoded by this gene (p35) is a neuron-specific activator of cyclin-dependent kinase 5 (CDK5); the activation of CDK5 is required for proper development of the central nervous system. The p35 form of this protein is proteolytically cleaved by calpain, generating a p25 form. The cleavage of p35 into p25 results in relocalization of the protein from the cell periphery to nuclear and perinuclear regions. P25 deregulates CDK5 activity by prolonging its activation and changing its cellular location. The p25 form accumulates in the brain neurons of patients with Alzheimer's disease. This accumulation correlates with an increase in CDK5 kinase activity, and may lead to aberrantly phosphorylated forms of the microtubule-associated protein tau, which contributes to Alzheimer's disease. [provided by RefSeq, Jul 2008]

Function: p35 is a neuron specific activator of CDK5. The complex p35/CDK5 is required for neurite outgrowth and cortical lamination. Involved in dendritic spine morphogenesis by mediating the EFNA1-EPHA4 signaling. Activator of TPKII.

Subunit structure: Heterodimer composed of a catalytic subunit CDK5 and a regulatory subunit CDK5R1 (p25) and macromolecular complex composed of at least CDK5, CDK5R1 (p35) and CDK5RAP1 or CDK5RAP2 or CDK5RAP3. Only the heterodimer shows kinase activity. Interacts with EPHA4 and NGEF; may mediate the activation of NGEF by EPHA4

By similarity. Interacts with RASGRF2. Ref.8 Ref.10

Subcellular location: Cyclin-dependent kinase 5 activator 1, p35: Cell membrane; Lipid-anchor; Cytoplasmic side

Probable. Note: In the primary cortical neurons, p35 is present in the peripheries and nerve terminals. Ref.6 Ref.10 Ref.11Cyclin-dependent kinase 5 activator 1, p25: Nucleus. Cytoplasm › perinuclear region. Note: The conversion of p35 to p25 relocalizes the protein from the cell periphery to the cytoplasm, in nuclear and perinuclear regions. In the primary cortical neurons, p25 is primarily concentrated in the cell soma and is largely absent from neurites. Ref.6 Ref.10 Ref.11

Tissue specificity: Brain and neuron specific.

Post-translational modification: The p35 form is proteolytically cleaved by calpain, giving rise to the p25 form. P35 has a 5 to 10 fold shorter half-life compared to p25. The conversion results in deregulation of the CDK5 kinase: p25/CDK5 kinase displays an increased and altered tau phosphorylation in comparison to the p35/CDK5 kinase in vivo

By similarity.Myristoylated. A proper myristoylation signal is essential for the proper distribution of p35.Ubiquitinated. Degradation of p35 by proteasome results in down-regulation of CDK5 activity. During this process, CDK5 phosphorylates p35 and induces its ubiquitination and subsequent degradation. Ref.7Phosphorylation at Ser-8 and Thr-138 by CDK5 prevents calpain-mediated proteolysis.

Miscellaneous: Cleavage of p35 to p25 may be involved in the pathogenesis of cytoskeletal abnormalities and neuronal death in neurodegenerative diseases. The p25 form accumulates in neurons in the brain of patients with Alzheimer disease, but not in normal brain. This accumulation correlates with an increase in CDK5 kinase activity. Application of amyloid beta peptide A-beta(1-42) induced the conversion of p35 to p25 in primary cortical neurons. Expression of the p25/Cdk5 complex in cultured primary neurons induces cytoskeletal disruption, morphological degeneration and apoptosis.

Sequence similarities: Belongs to the cyclin-dependent kinase 5 activator family.