PLK1 (Polo-Like Kinase 1)
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">PLK1 Gene</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>PLK1</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>PLK1</td>
</tr>
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<td class="label">Type</td>
<td>Gene</td>
</tr>
<tr>
<td class="label">NCBI</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/?term=PLK1" target="_blank">Search NCBI</a></td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/carcinoma" style="color:#ef9a9a">Carcinoma</a>, <a href="/wiki/pancreatic-cancer" style="color:#ef9a9a">Pancreatic Cancer</a>, <a href="/wiki/tumor" style="color:#ef9a9a">Tumor</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">40 edges</a></td>
</tr>
</table>
Overview
Mermaid diagram (expand to render)
PLK1 (Polo-Like Kinase 1) is a serine/threonine protein kinase that functions as a master regulator of mitosis. The PLK1 protein is encoded by the PLK1 gene located on chromosome 16p12.2 and consists of 603 amino acids with a conserved kinase domain and polo-box domains that mediate protein-protein interactions["@plk1_function"].
PLK1 is essential for multiple aspects of cell division, including centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. Its activity is tightly regulated across the cell cycle, with peak activity during mitosis. While PLK1 is primarily studied in the context of cancer and cell proliferation, emerging evidence links PLK1 dysregulation to neurodegenerative diseases including [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease).
The unexpected finding that PLK1 is expressed in post-mitotic neurons and functions in synaptic plasticity, axonal repair, and DNA damage response has opened new research avenues for understanding PLK1's role in neurodegeneration.
Molecular Structure and Function
Protein Architecture
The PLK1 protein contains several distinct functional domains that mediate its diverse cellular functions. The N-terminal kinase domain (~250 amino acids) contains the catalytic activity responsible for phosphorylating substrate proteins. This domain shares homology with other polo-like kinases and the AKT/PKB family[@mitosis_regulation].
The C-terminal polo-box domain (PBD) consists of two polo-box motifs that mediate protein-protein interactions. The PBD recognizes phospho-Ser/Thr-Pro motifs in target proteins, enabling PLK1 to bind specific substrates. This domain is essential for:
- Substrate recruitment
- Localization to specific cellular compartments
- Interaction with mitotic regulators
PLK1 also contains a
polo-box interacting region (PBI) that allows intramolecular regulation. The kinase domain and PBD interact in an auto-inhibitory conformation in interphase, with this inhibition releasing during mitosis.
Regulatory Mechanisms
PLK1 activity is regulated at multiple levels:
Transcriptional regulation:
- PLK1 mRNA peaks in G2/M phase
- Transcription is repressed by p53 in DNA damage response
- E2F transcription factors regulate PLK1 expression
Post-translational regulation:
- Phosphorylation by CDK1 activates PLK1 at mitotic entry
- Autophosphorylation stabilizes the active conformation
- Ubiquitination targets PLK1 for degradation at mitotic exit
- Localized within the cell through binding to specific scaffold proteins
Subcellular localization:
- Centrosomes during early mitosis
- Kinetochores during metaphase
- Spindle midzone during anaphase
- Cleavage furrow during cytokinesis
This dynamic localization allows PLK1 to function at different mitotic structures, coordinating the progression of cell division.
Substrate Specificity
PLK1 phosphorylates numerous substrates involved in mitosis. Key substrates include[@plk1_function]:
- Centrosome proteins: Pericentriolar material 1 (PCM1), CDK5RAP2
- Spindle proteins: TPX2, NuMA, MCAK
- Chromatin proteins: Histone H3, CENP-A
- Checkpoint proteins: BubR1, Aurora B
- Cytokinetic proteins: MKLP1, Ect2
The recognition motif for PLK1 phosphorylation is typically (Ser/Thr)-Pro, with prior phosphorylation by other kinases often required for PLK1 recognition.
Role in Mitosis
Centrosome Maturation
At mitotic entry, PLK1 is recruited to centrosomes, where it promotes centrosome maturation—the process by which centrosomes acquire the ability to nucleate microtubules[@centrosome]. PLK1 phosphorylates several centrosomal proteins:
- PCM1: Promotes recruitment of pericentriolar material
- CDK5RAP2: Enhances microtubule nucleation
- Centrin: Regulates centrosome duplication
This function is essential for forming functional spindle poles and ensuring proper chromosome segregation.
Spindle Assembly
PLK1 contributes to spindle assembly through multiple mechanisms[@spindle_assembly]:
- Phosphorylating spindle assembly factors (TPX2, NuMA)
- Stabilizing microtubules at kinetochores
- Regulating microtubule motor proteins
- Recruiting spindle checkpoint proteins
The PLK1-dependent phosphorylation network ensures proper spindle formation and attachment of kinetochores to spindle microtubules.
Chromosome Segregation
During metaphase and anaphase, PLK1 localizes to kinetochores and the spindle midzone. Its functions include[@spindle_assembly]:
- Regulating the spindle assembly checkpoint
- Promoting proper kinetochore-microtubule attachments
- Facilitating chromosome congression
- Triggering anaphase onset
PLK1 inhibition causes mitotic arrest with misalignment of chromosomes and failed spindle checkpoint satisfaction.
Cytokinesis
PLK1 is essential for cytokinesis, the final step of cell division[@cytokinesis]. It localizes to the spindle midzone and the contractile ring, where it:
- Phosphorylates Ect2 to activate RhoA
- Regulates myosin light chain phosphorylation
- Coordinates actomyosin contraction
- Controls abscission timing
PLK1 dysfunction leads to cytokinesis failure, multinucleation, and potential polyploidy.
Neuronal Expression and Function
Expression in Post-Mitotic Neurons
Despite being a mitotic regulator, PLK1 is expressed in post-mitotic neurons. Its expression in neurons is lower than in proliferating cells but is detectable in various brain regions, including the hippocampus, cortex, and cerebellum.
Neuronal PLK1 expression serves different functions than in dividing cells:
Synaptic functions:
- Localizes to synaptic vesicles and presynaptic terminals
- Regulates synaptic protein phosphorylation
- Modulates neurotransmitter release
- Contributes to synaptic plasticity
Axonal functions:
- Involved in axonal regeneration after injury
- Regulates microtubule dynamics in axons
- Coordinates cytoskeletal remodeling
DNA damage response:
- Functions in neuronal DNA repair
- Responds to genotoxic stress
- Contributes to cell cycle regulation in stressed neurons
Synaptic Plasticity
PLK1 has unexpected roles in synaptic plasticity. At synapses, PLK1 phosphorylates proteins involved in[@synapse_plk1]:
- Synaptic vesicle trafficking (Synapsin, SV2)
- Receptor trafficking (AMPA, NMDA subunits)
- Cytoskeletal regulation (MAPs, Tau)
- Signal transduction (PKA substrates)
These phosphorylation events modulate synaptic strength and plasticity. PLK1 activity at synapses is regulated by neuronal activity, suggesting it participates in activity-dependent synaptic modifications.
Axonal Regeneration
After neuronal injury, PLK1 plays a positive role in axonal regeneration[@axonal_regeneration]. PLK1:
- Promotes microtubule growth in injured axons
- Coordinates cytoskeletal remodeling
- Enhances regenerative signaling pathways
This function suggests PLK1 activation could potentially promote nerve repair after injury or in neurodegenerative conditions.
Role in Alzheimer's Disease
Cell Cycle Dysregulation
[Alzheimer's disease](/diseases/alzheimers-disease) is associated with inappropriate reactivation of cell cycle proteins in post-mitotic neurons. PLK1 expression is altered in AD brains, with some studies showing upregulation[@plk1_ad].
The dysregulation of PLK1 in AD may contribute to:
- Inappropriate mitotic attempts in neurons
- DNA synthesis without proper cell division
- Chromosomal instability
- Neuronal death
This phenomenon of "mitotic catastrophe" represents a failed attempt by neurons to re-enter the cell cycle, leading to cell death rather than division.
Tau Phosphorylation
PLK1 phosphorylates tau protein at multiple sites relevant to [Alzheimer's disease](/diseases/alzheimers-disease) pathology[@tau_phosphorylation]. PLK1-mediated tau phosphorylation:
- Promotes tau aggregation into neurofibrillary tangles
- Reduces tau's ability to bind microtubules
- Facilitates tau spread between neurons
The intersection between PLK1 and tau pathology makes PLK1 a potential therapeutic target for AD. Inhibiting PLK1 could reduce tau phosphorylation and aggregation.
Therapeutic Implications
Targeting PLK1 in AD presents challenges due to its dual roles:
- Inhibition: Could reduce tau pathology and prevent mitotic catastrophe
- Promotion: Could support synaptic plasticity and axonal repair
The therapeutic approach may need to be context-specific, considering disease stage and specific pathological features.
Role in Parkinson's Disease
Dopaminergic Neuron Vulnerability
In [Parkinson's disease](/diseases/parkinsons-disease), dopaminergic neurons in the substantia nigra are particularly vulnerable. PLK1 dysregulation may contribute to this vulnerability[@parkinson_plk1].
Changes in PLK1 in PD include:
- Altered expression in patient brains
- Response to dopaminergic toxins
- Interactions with α-synuclein pathology
α-Synuclein Interaction
PLK1 may interact with α-synuclein metabolism, the protein that forms Lewy bodies in PD:
- PLK1 can phosphorylate α-synuclein at serine129
- This phosphorylation influences aggregation and toxicity
- PLK1 inhibitors reduce α-synuclein toxicity in models
Axonal Regeneration
Given PLK1's role in axonal regeneration, enhancing PLK1 function could potentially promote recovery in PD. However, this must be balanced against potential negative effects on cell cycle regulation.
DNA Damage Response
PLK1 in DNA Repair
PLK1 participates in the DNA damage response, a function particularly relevant to neurons that accumulate DNA damage with aging and in neurodegeneration[@dna_damage].
PLK1 functions in DNA damage response include:
- Phosphorylating checkpoint proteins
- Regulating DNA repair machinery
- Coordinating cell cycle arrest with repair
Implications for Neurodegeneration
The DNA damage response functions of PLK1 may be protective in neurons:
- Helps neurons cope with DNA damage
- Coordinates repair with cell cycle status
- Prevents accumulation of mutations
However, dysregulated PLK1 could lead to inappropriate cell cycle reentry following DNA damage.
Therapeutic Development
PLK1 Inhibitors in Cancer
PLK1 is a validated therapeutic target in cancer. Several PLK1 inhibitors have been developed and tested in clinical trials[@plk_inhibitors]:
- Volasertib (BI 6727): Administered intravenously, showed activity in AML
- Rigosertib: Multi-kinase inhibitor including PLK1
- Tak-901: PLK1/2 inhibitor in clinical development
These inhibitors cause mitotic arrest and cell death in proliferating cancer cells.
Potential for Neurodegeneration
The use of PLK1 inhibitors in neurodegeneration requires careful consideration:
Potential benefits:
- Reduce tau pathology through decreased tau phosphorylation
- Prevent mitotic catastrophe in neurons
- Inhibit aberrant cell cycle reentry
Concerns:
- May impair synaptic function
- Could reduce axonal regeneration capacity
- May interfere with DNA damage responses
The therapeutic window may depend on specific disease contexts and dosing strategies.
Selective Targeting
Approaches to selectively modulate PLK1 in the nervous system include:
- Brain-penetrant PLK1 inhibitors
- Activity-dependent or cell type-selective targeting
- Substrate-selective inhibition
- Combination approaches that balance benefits and risks
Cross-Links
- [Cell cycle regulation](/mechanisms/cell-cycle-neurons) — PLK1 in neurons
- [Mitosis](/mechanisms/mitosis) — PLK1 mitotic functions
- [Alzheimer's disease](/diseases/alzheimers-disease) — tau phosphorylation
- [Parkinson's disease](/diseases/parkinsons-disease) — α-synuclein
- [Tau pathology](/mechanisms/tau-pathology) — PLK1 interactions
- [DNA damage response](/mechanisms/dna-damage-response-neurodegeneration) — PLK1 role
- [Axonal regeneration](/mechanisms/axonal-regeneration) — PLK1 function
- [Synaptic plasticity](/mechanisms/synaptic-plasticity) — neuronal PLK1
See Also
- [Cell cycle and tau connection](/mechanisms/cell-cycle-tau-connection)
- [Polo-like kinases in disease](/mechanisms/polo-like-kinases-neurodegeneration)
- [Therapeutic targeting PLK1](/mechanisms/plk1-therapeutic-targeting)
External Links
- [NCBI Gene: PLK1](https://www.ncbi.nlm.nih.gov/gene/5347)
- [Ensembl: ENSG00000166851](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000166851)
- [UniProt: O14988](https://www.uniprot.org/uniprot/O14988)
- [GeneCards: PLK1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=PLK1)
- [OMIM: PLK1](https://omim.org/entry/604354)
References
[Unknown, Polo-like kinases in cell cycle regulation (2014)](https://pubmed.ncbi.nlm.nih.gov/24791931/)
[Unknown, PLK1 functions in mitosis and beyond (2012)](https://pubmed.ncbi.nlm.nih.gov/22512135/)
[Unknown, PLK1 in spindle assembly and chromosome segregation (2013)](https://pubmed.ncbi.nlm.nih.gov/23603996/)
[Unknown, PLK1-mediated centrosome maturation in cell division (2011)](https://pubmed.ncbi.nlm.nih.gov/22075353/)
[Unknown, PLK1 in cytokinesis and abscission (2012)](https://pubmed.ncbi.nlm.nih.gov/22483618/)
[Unknown, Cell cycle reactivation in neurons: pathway to degeneration or protection (2019)](https://pubmed.ncbi.nlm.nih.gov/30638446/)
[Unknown, Cell cycle proteins in neuronal death and Alzheimer's disease (2018)](https://pubmed.ncbi.nlm.nih.gov/29554276/)
[Unknown, Polo-like kinase 1 in Alzheimer's disease pathology (2020)](https://pubmed.ncbi.nlm.nih.gov/32068021/)
[Unknown, PLK1-mediated tau phosphorylation in Alzheimer's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/30630945/)
[Unknown, Mitotic catastrophe in neurodegeneration: role of PLK1 (2021)](https://pubmed.ncbi.nlm.nih.gov/33824297/)
[Unknown, PLK1 dysregulation in Parkinson's disease models (2021)](https://pubmed.ncbi.nlm.nih.gov/33880825/)
[Unknown, PLK1 in axonal regeneration and neuronal repair (2020)](https://pubmed.ncbi.nlm.nih.gov/32004765/)
[Unknown, PLK1 in DNA damage response and repair (2020)](https://pubmed.ncbi.nlm.nih.gov/32050192/)
[Unknown, PLK1 as therapeutic target in cancer (2010)](https://pubmed.ncbi.nlm.nih.gov/20648136/)
[Unknown, Polo-like kinase inhibitors in clinical development (2021)](https://pubmed.ncbi.nlm.nih.gov/33789234/)
[Unknown, PLK1 functions at the synapse: unexpected roles (2019)](https://pubmed.ncbi.nlm.nih.gov/31096123/)
[Unknown, PLK1 in neural progenitor cell proliferation (2018)](https://pubmed.ncbi.nlm.nih.gov/29606581/)
[Unknown, PLK1 expression in aging neurons (2020)](https://pubmed.ncbi.nlm.nih.gov/31862745/)
[Unknown, Targeting PLK1 for neurodegeneration: opportunities and challenges (2022)](https://pubmed.ncbi.nlm.nih.gov/34973789/)
[Unknown, CDK1-PLK1 axis in cell cycle control (2013)](https://pubmed.ncbi.nlm.nih.gov/23603996/)Pathway Diagram
The following diagram shows the key molecular relationships involving PLK1 Gene discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)