CDK5R2 (Cyclin-Dependent Kinase Regulatory Subunit 2)
<div class="infobox infobox-gene"> [@tsai2001]Gene Symbol | CDK5R2 |Full Name | Cyclin-Dependent Kinase 5 Regulatory Subunit 2 |Chromosomal Location | 2q35 |NCBI Gene ID | [8941](https://www.ncbi.nlm.nih.gov/gene/8941) |Ensembl ID | ENSG00000100157 |UniProt ID | [Q16569](https://www.uniprot.org/uniprot/Q16569) |Protein Name | Cyclin-dependent kinase 5 activator 2 (p39) |Expression | Neuron-specific |
Overview
flowchart TD
CDK5R2["CDK5R2"] -->|"therapeutic target"| Encephalitis["Encephalitis"]
CDK5R2["CDK5R2"] -->|"associated with"| Inflammation["Inflammation"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| ISG15["ISG15"]
CDK5R2["CDK5R2"] -->|"associated with"| GRM5["GRM5"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| GRM5["GRM5"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| SCN2B["SCN2B"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| STAT1["STAT1"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| SCN8A["SCN8A"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| SLC17A7["SLC17A7"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| FGF13["FGF13"]
CDK5R2["CDK5R2"] -->|"therapeutic target"| Cdk5["Cdk5"]
CDK5R2["CDK5R2"] -->|"interacts with"| FGF13["FGF13"]
CDK5R2["CDK5R2"] -->|"interacts with"| GRM5["GRM5"]
CDK5R2["CDK5R2"] -->|"interacts with"| ISG15["ISG15"]
style CDK5R2 fill:#4fc3f7,stroke:#333,color:#000
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CDK5R2 (Cyclin-Dependent Kinase Regulatory Subunit 2)
<div class="infobox infobox-gene"> [@tsai2001]Gene Symbol | CDK5R2 |Full Name | Cyclin-Dependent Kinase 5 Regulatory Subunit 2 |Chromosomal Location | 2q35 |NCBI Gene ID | [8941](https://www.ncbi.nlm.nih.gov/gene/8941) |Ensembl ID | ENSG00000100157 |UniProt ID | [Q16569](https://www.uniprot.org/uniprot/Q16569) |Protein Name | Cyclin-dependent kinase 5 activator 2 (p39) |Expression | Neuron-specific |
Overview
Mermaid diagram (expand to render)
CDK5R2 (also known as p39 ) is a neuron-specific gene that encodes a regulatory subunit of [CDK5](/proteins/cdk5), a proline-directed serine/threonine kinase critical for neuronal function. Unlike its ubiquitously expressed paralog [CDK5R1](/genes/cdk5r1) (p35), p39 is enriched in the brain and plays distinct roles in neuronal development, synaptic plasticity, and myelination. Variants in CDK5R2 have been associated with [Alzheimer's Disease](/diseases/alzheimers-disease) and other neurodegenerative conditions through dysregulation of tau phosphorylation and synaptic homeostasis.
Normal Function
CDK5 Activation CDK5R2 encodes p39, which forms an active complex with [CDK5](/proteins/cdk5):
Neuron-specific activation : p39 expression is largely restricted to neurons, making CDK5 activity in the brain uniquely regulated by this activatorAlternative splicing : The CDK5R2 gene produces multiple isoforms with different tissue distributions and regulatory propertiesCalcium-dependent activation : p39 cleavage by calpain produces p25, a hyperactive fragment similar to p35 cleavage in disease statesRoles in Neuronal Biology p39/CDK5 signaling regulates multiple neuronal processes:
| Process | Function | Key Targets |Neuronal Development | Axon guidance, dendrite formation | CRMPs, MAPs |Synaptic Plasticity | Long-term potentiation, memory formation | Synaptic receptors, PSD proteins |Myelination | Oligodendrocyte differentiation | MBP, PLP |Cell Cycle Control | Neuronal cell cycle exit | Rb, E2F proteins |
Interaction with p35 (CDK5R1) CDK5R2 and [CDK5R1](/genes/cdk5r1) have overlapping but distinct functions:
p35 (CDK5R1) is expressed earlier in development
p39 (CDK5R2) becomes dominant in mature neurons
Both activators can compensate for each other's loss
p39 knockout mice show more severe neurological phenotypes than p35 knockouts
Protein Structure The p39 protein contains:
N-terminal region : Regulatory domain responsible for CDK5 binding and activationCentral region : Contains cleavage sites for calpain-mediated conversion to p25C-terminal domain : Required for proper subcellular localizationDisease Associations
Alzheimer's Disease CDK5R2 dysregulation contributes to AD pathogenesis through multiple mechanisms:
Tau Hyperphosphorylation : Enhanced CDK5/p39 activity leads to excessive tau phosphorylation at AD-relevant epitopes (Ser202, Thr231, Ser396)Synaptic Dysfunction : Alters synaptic protein phosphorylation, impairing neurotransmissionAmyloid-β Interaction : Aβ can activate calpain, leading to p39 cleavage and CDK5 hyperactivationNeuroinflammation : CDK5/p39 signaling modulates microglial activation and inflammatory responses
Other Neurodegenerative Conditions
Parkinson's Disease : Altered expression in dopaminergic neuronsAmyotrophic Lateral Sclerosis (ALS) : Dysregulated in motor neuronsHuntington's Disease : Implicated in mutant huntingtin toxicityGenetic Associations Genome-wide association studies (GWAS) have linked CDK5R2 variants to:
Alzheimer's disease risk
Cognitive decline in aging
Schizophrenia susceptibility
Expression Patterns
Brain Regional Distribution p39 is expressed throughout the brain with highest levels in:
Cerebral cortex : Especially layer V pyramidal neuronsHippocampus : CA1-CA3 regions, dentate gyrusCerebellum : Purkinje cellsBasal ganglia : Striatal medium spiny neuronsCellular Localization
Cytosolic : Majority of p39 is cytosolicMembrane-associated : Subset localizes to synapsesNeuronal processes : Present in axons and dendritesResearch Findings
Key Publications
[Tsai et al., 2001](https://doi.org/10.1016/S0092-8674(01)00491-3) - Original characterization of p39 function in neurons
[Liu et al., 2007](https://doi.org/10.1016/j.tins.2007.04.003) - Comprehensive review of p39 in neuronal function
[Czonka et al., 2021](https://doi.org/10.1007/s12035-021-02345-8) - CDK5R2 role in neurodegeneration mechanisms
[Shah et al., 2009](https://doi.org/10.1016/j.neuroscience.2009.02.053) - CDK5R2 in brain development
Therapeutic Implications CDK5/p39 activity represents a potential therapeutic target:
Inhibitor development : Small molecules targeting the CDK5/p39 complexCalpain inhibition : Preventing p25 generation from p39Gene therapy : Modulating CDK5R2 expression levelsInteractions
Protein Interactions CDK5R2/p39 interacts with:
[CDK5](/proteins/cdk5) - Primary binding partner
[Tau](/proteins/tau) - Phosphorylation substrate
[DARPP-32](/proteins/darpp32) - Modulator of CDK5 activity
[p35](/proteins/p35) - Can form heterodimers
Synaptic proteins (PSD95, Synapsin)
Pathway Membership
[CDK5 Signaling Pathway](/mechanisms/cdk5-signaling)
[Tau Phosphorylation Pathway](/mechanisms/tau-phosphorylation)
[Synaptic Plasticity Mechanisms](/mechanisms/synaptic-plasticity)
[Neuronal Development](/mechanisms/neuronal-development)
Related Pages
[CDK5 Protein](/proteins/cdk5)
[CDK5R1 Gene](/genes/cdk5r1)
[CDK5 Signaling](/mechanisms/cdk5-signaling)
[Tau Phosphorylation](/mechanisms/tau-phosphorylation)
[Synaptic Plasticity](/mechanisms/synaptic-plasticity)
[Alzheimer's Disease](/diseases/alzheimers-disease)
See Also
[CDK5 Signaling](/mechanisms/cdk5-signaling)
[Tau Biology](/mechanisms/tau-biology)
[Synaptic Plasticity](/mechanisms/synaptic-plasticity)
[Neurodegeneration Mechanisms](/diseases/neurodegeneration)
External Links
[NCBI Gene: CDK5R2](https://www.ncbi.nlm.nih.gov/gene/8941)
[Ensembl: ENSG00000100157](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100157)
[UniProt: Q16569](https://www.uniprot.org/uniprot/Q16569)
[GeneCards: CDK5R2](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CDK5R2)
[OMIM: CDK5R2](https://omim.org/search?search=CDK5R2)
[Allen Brain Atlas: CDK5R2](https://human.brain-map.org/microarray/search/show?search_term=CDK5R2)
== References ==
References
[Tsai et al., p39 function in neurons (2001) (2001)](/[DOI:10.1016/S0092-8674(01)00491-3](https://doi.org/10.1016/S0092-8674(01)00491-3))
[Dhavan et al., CDK5 and synaptic plasticity (2002) (2002)](https://doi.org/10.1038/nrn727)
[Shah et al., CDK5R2 in brain development (2009) (2009)](https://doi.org/10.1016/j.neuroscience.2009.02.053)
[Liu et al., p39 in neuronal function (2007) (2007)](https://doi.org/10.1016/j.tins.2007.04.003)
[Czonka et al., CDK5R2 in neurodegeneration (2021) (2021)](https://doi.org/10.1007/s12035-021-02345-8)
Pathway Diagram The following diagram shows the key molecular relationships involving CDK5R2 Gene discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)
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