PLK1 Gene

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>
<tr>
<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

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>
<tr>
<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

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

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

• 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

• Centrosomes during early mitosis
• Kinetochores during metaphase
• Spindle midzone during anaphase
• Cleavage furrow during cytokinesis

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

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

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

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

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

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

• Involved in axonal regeneration after injury
• Regulates microtubule dynamics in axons
• Coordinates cytoskeletal remodeling

• 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)

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

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

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

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

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

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

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

• May impair synaptic function
• Could reduce axonal regeneration capacity
• May interfere with DNA damage responses

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

Pathway Diagram

The following diagram shows the key molecular relationships involving PLK1 Gene discovered through SciDEX knowledge graph analysis: