Related Experiment Video
Updated: Aug 25, 2026
Using Live-Cell Imaging to Measure the Effects of Pathological Proteins on Axonal Transport in Primary Hippocampal Neurons
Published on: December 22, 2023
Effects of cyclin-dependent kinase-5 activity on apoptosis and tau phosphorylation in immortalized mouse brain
Shirley B Shelton1, Pavan Krishnamurthy, Gail V W Johnson
1Department of Psychiatry, University of Alabama at Birmingham, Birmingham, Alabama 35294-0001, USA.
Abstract:
Cyclin-dependent kinase-5 (CDK5), a unique CDK family member, is active primarily in the central nervous system (CNS). Previous studies suggest that CDK5 is proapoptotic and contributes to tau hyperphosphorylation and neurodegeneration in Alzheimer's disease. The objective of this study was to examine CDK5 effects on apoptotic progression and tau phosphorylation. Immortalized embryonic mouse brain cortical cells were used to establish a stable cell line that overexpressed wild-type human tau. In these studies, thapsigargin, which induces endoplasmic reticulum stress and can cause accumulation of misfolded proteins, was used to induce apoptosis. Caspase-3 activity and poly-(ADP-ribose)-polymerase (PARP) cleavage, as measures of apoptosis, were significantly increased 24 and 48 hr after thapsigargin treatment, and these events were unaffected by tau expression. Although transient coexpression of CDK5 and its activator, p25, increased CDK5 activity greater than tenfold, increases in caspase-3 activity in response to thapsigargin treatment were unaffected by the presence of CDK5/p25. Tau phosphorylation at the PHF-1 epitope, but not the Tau-1 epitope, was increased significantly in CDK5/p25-transfected cells compared to cells transfected with dominant negative CDK5 (DNCDK5). The PHF-1 epitope remained phosphorylated until 48 hr after thapsigargin treatment in the CDK5/p25-transfected cells. Over the course of apoptosis in this model, phosphorylation of the Tau-1 epitope was unaffected in cells transfected with DNCDK5, vector, or CDK5/p25. In summary, these results demonstrate that CDK5 does not have a significant impact on tau phosphorylation and thapsigargin-induced apoptosis in this neuronal cell model.
Insights
Cyclin-dependent kinase-5 (CDK5) did not significantly impact tau phosphorylation or thapsigargin-induced apoptosis in this neuronal cell model, despite increased CDK5 activity.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Cyclin-dependent kinase-5 (CDK5) is primarily active in the central nervous system (CNS).
- Previous research suggests CDK5 promotes apoptosis and tau hyperphosphorylation, contributing to Alzheimer's disease neurodegeneration.
- The role of CDK5 in apoptosis and tau phosphorylation requires further investigation.
Purpose of the Study:
- To investigate the effects of CDK5 on apoptotic progression.
- To examine CDK5's influence on tau phosphorylation.
- To understand CDK5's role in neurodegenerative disease models.
Main Methods:
- Established a stable cell line overexpressing wild-type human tau in immortalized embryonic mouse brain cortical cells.
- Induced apoptosis using thapsigargin to trigger endoplasmic reticulum stress and protein misfolding.
- Assessed apoptosis via caspase-3 activity and poly-(ADP-ribose)-polymerase (PARP) cleavage.
- Manipulated CDK5 activity through coexpression with its activator p25 or dominant-negative CDK5 (DNCDK5).
Main Results:
- Thapsigargin treatment significantly increased caspase-3 activity and PARP cleavage, indicative of apoptosis, irrespective of tau expression.
- Coexpression of CDK5 and p25 elevated CDK5 activity but did not alter thapsigargin-induced caspase-3 activity.
- CDK5/p25 transfection increased tau phosphorylation at the PHF-1 epitope, which persisted throughout apoptosis, but did not affect the Tau-1 epitope phosphorylation.
- Phosphorylation of the Tau-1 epitope remained unchanged across different transfection conditions (DNCDK5, vector, CDK5/p25) during apoptosis.
Conclusions:
- CDK5 does not significantly influence thapsigargin-induced apoptosis in this neuronal cell model.
- CDK5 activity, even when elevated, does not alter the apoptotic pathway triggered by endoplasmic reticulum stress.
- While CDK5/p25 affects specific tau phosphorylation sites (PHF-1), it does not broadly impact tau phosphorylation during apoptosis in this context.
