Tamoxifen Inhibits CDK5 Kinase Activity by Interacting with p35/p25 and Modulates the Pattern of Tau Phosphorylation

Abstract

Cyclin-dependent kinase 5 (CDK5) is a multifunctional enzyme that plays numerous roles, notably in brain development. CDK5 is activated through its association with the activators, p35 and p39, rather than by cyclins. Proteolytic procession of the N-terminal part of its activators has been linked to Alzheimer's disease and various other neuropathies. The interaction with the proteolytic product p25 prolongs CDK5 activation and modifies the substrate specificity. In order to discover small-molecule inhibitors of the interaction between CDK5 and p25, we have used a bioluminescence resonance energy transfer (BRET)-based screening assay. Among the 1,760 compounds screened, the generic drug tamoxifen has been identified. The inhibition of the CDK5 activity by tamoxifen was notably validated by monitoring the phosphorylation state of tau protein. The study of the molecular mechanism of inhibition indicates that tamoxifen interacts with p25 to block the CDK5/p25 interaction and pave the way for new treatments of tauopathies.

Fluorescent Biosensor of CDK5 Kinase Activity in Glioblastoma Cell Extracts and Living Cells

“…[ 42,43 ] 6His‐p25 and 6His‐Cyclin A were expressed in E. coli by IPTG induction and purified on Ni‐NTA resin. [ 42–44 ] GST‐CDK5/6Hisp25 complex was formed following individual purification of each subunit and stoichiometric incubation, then further incubated with GST‐CIV to (ensure complete activation). GST‐CDK2/6HisCyclinA complex was formed by incubating 6His‐CyclinA with GST‐CDK2 on the GST affinity column, prior to elution.…”

La levure modèle et outil… aussi pour la recherche thérapeutique

“…Le suivi de l'activité luciférase permet aussi d'évaluer la cytotoxicité des molécules analysées. Plusieurs criblages ont été mis en oeuvre afin d'identifier des inhibiteurs de l'interaction CDK5/p25, une protéine kinase impliquée notamment dans divers troubles neurodégénératifs [58,59] et de nouveaux antibactériens, inhibiteurs de l'interaction entre la sous-unité b' et le facteur d'initiation s 70 de l'ARN polymérase bactérienne [60]. L'utilisation de nouveaux substrats de luciférase, de la NanoLuc® et de nouveaux couples donneur/ accepteur (mutants de la luciférase et de l'accepteur, tels que la mVenus ou encore la mTurquoise) permettront d'augmenter la sensibilité et l'usage du BRET dans la levure pour y étudier de nouvelles IPP [57].…”

Biological functions of CDK5 and potential CDK5 targeted clinical treatments

“…Recently, tamoxifen (TMX), a drug currently used in breast cancer treatment, was found to decrease CDK5 activation by competitively binding with p35 and p25, and preventing their activation of CDK5. While the TMX inhibition of CDK5 activity could contribute to the anti-tumor effects of the drug, TMX treatment was also found to decrease Tau phosphorylation, suggesting a use for tamoxifen in treating Alzheimer's disease [66]. However, because of the broad functions of CDK5 in different cell and tissue types and the pan CDK inhibitory effect on other family members, the off target affects of a CDK5 inhibitory drug may create undesirable side effects.…”