lrrk2-protein

LRRK2 (Dardarin) Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4ea;">LRRK2 — Leucine-Rich Repeat Kinase 2</th></tr>
<tr><td><b>Gene</b></td><td>LRRK2</td></tr>
<tr><td><b>UniProt ID</b></td><td>[Q5S007](https://www.uniprot.org/uniprot/Q5S007)</td></tr>
<tr><td><b>PDB Structures</b></td><td>6VP6, 7LHW, 7LI4, 4D0G</td></tr>
<tr><td><b>Molecular Weight</b></td><td>286 kDa (2527 aa)</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Cytoplasm, membranes, mitochondria</td></tr>
<tr><td><b>Protein Family</b></td><td>ROCO family (Kinase + GTPase)</td></tr>
<tr><td><b>Domain Architecture</b></td><td>ARM, ANK, LRR, ROC, COR, Kinase</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1183 edges</a></td>
</tr>
</table>
</div>

Overview

LRRK2 (Leucine-Rich Repeat Kinase 2), also known as Dardarin (from the Basque "dardara" meaning "trembling"), is a large multi-domain protein encoded by the LRRK2 gene. It belongs to the ROCO protein family and is one of the most significant genetic risk factors for Parkinson's disease[@muller2023].

Domain Architecture

LRRK2 (Dardarin) Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4ea;">LRRK2 — Leucine-Rich Repeat Kinase 2</th></tr>
<tr><td><b>Gene</b></td><td>LRRK2</td></tr>
<tr><td><b>UniProt ID</b></td><td>[Q5S007](https://www.uniprot.org/uniprot/Q5S007)</td></tr>
<tr><td><b>PDB Structures</b></td><td>6VP6, 7LHW, 7LI4, 4D0G</td></tr>
<tr><td><b>Molecular Weight</b></td><td>286 kDa (2527 aa)</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Cytoplasm, membranes, mitochondria</td></tr>
<tr><td><b>Protein Family</b></td><td>ROCO family (Kinase + GTPase)</td></tr>
<tr><td><b>Domain Architecture</b></td><td>ARM, ANK, LRR, ROC, COR, Kinase</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1183 edges</a></td>
</tr>
</table>
</div>

Overview

LRRK2 (Leucine-Rich Repeat Kinase 2), also known as Dardarin (from the Basque "dardara" meaning "trembling"), is a large multi-domain protein encoded by the LRRK2 gene. It belongs to the ROCO protein family and is one of the most significant genetic risk factors for Parkinson's disease[@muller2023].

Domain Architecture

LRRK2 has a complex multi-domain structure:

Key Domains

| Domain | Function | Disease Relevance |
|--------|----------|-------------------|
| LRR | Protein-protein interactions | Mutations may affect binding |
| ROC | GTPase activity | G2019S increases kinase activity |
| COR | Kinase regulation | Autophosphorylation |
| Kinase | Phosphotransferase | Major drug target |
| WD40 | Scaffold function | C-terminal interactions |

Normal Function

GTPase Activity

• ROC domain hydrolyzes GTP to GDP
• Regulates protein conformation
• Autophosphorylation on multiple residues

Kinase Activity

• Phosphorylates substrate proteins
• Regulated by GTP binding to ROC domain
• Multiple autophosphorylation sites

Cellular Functions

• Dendritic arborization
• Synaptic formation
• Axon guidance

• MAPK pathway modulation
• Wnt signaling
• Inflammatory responses

• Macroautophagy regulation
• Lysosomal function
• Protein sorting

• Mitochondrial dynamics
• Mitophagy regulation
• Energy metabolism

LRRK2 in Parkinson's Disease

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Pathogenic Mechanisms

LRRK2 mutations cause PD through multiple mechanisms:

• G2019S (most common) increases kinase activity 2-3 fold
• Leads to enhanced substrate phosphorylation
• Causes toxic gain-of-function

• Impaired GTP hydrolysis
• Constitutive activation
• Altered protein interactions

• Impaired autophagy-lysosome pathway
• Mitochondrial dysfunction
• Synaptic defects

• Microglial activation
• Increased cytokine production
• Enhanced neuroinflammation

Cellular Consequences

Autophagy Dysregulation

LRRK2 hyperactivation impairs autophagy:

• mTORC1 hyperactivation: Prevents autophagy initiation
• Lysosomal dysfunction: Reduced clearance
• Protein aggregates: Accumulation

Mitochondrial Dysfunction

LRRK2 affects mitochondria:

• PINK1/Parkin pathway: Altered mitophagy
• Mitochondrial dynamics: fission/fusion imbalance
• Energy production: Reduced ATP

Synaptic Failure

Synaptic dysfunction in LRRK2 models:

• Vesicle cycling: Impaired release
• Spine morphology: Reduced spines
• Neurotransmission: Altered signaling

Common Pathogenic Mutations

| Mutation | Location | Effect | Frequency |
|----------|----------|--------|-----------|
| G2019S | Kinase | Increased activity | 5% familial, 1% sporadic |
| R1441C/G/H | ROC | Impaired GTPase | ~3% familial |
| N1437H | ROC | Reduced activity | Rare |
| G2385R | WD40 | Risk factor | 10% Asian populations |
| R1628P | WD40 | Risk factor | Higher in Asian |

Clinical Features of LRRK2-PD

Motor Symptoms

LRRK2-associated PD shows typical motor features:

• Resting tremor
• Bradykinesia
• Rigidity
• Postural instability

Non-Motor Symptoms

• Sleep disorders: REM sleep behavior disorder
• Olfactory dysfunction: Anosmia
• Autonomic dysfunction: Constipation

Therapeutic Targeting

LRRK2 is a major drug target for PD:

Kinase Inhibitors

Several LRRK2 inhibitors in development:

• DNL151/DNL312 (Denali) — Phase 1/2
• BIIB122 (Biogen) — Phase 2
• MLi-2 — Preclinical tool compound

Challenges

Structural Biology

Cryo-EM Structures

Recent advances have revealed the full-length LRRK2 structure[@alessi2023]:

Full-length architecture:

• L-shaped dimeric structure
• Coordinated Rock-Kinase module
• C-terminal WD40 scaffold

• Back-to-back dimer formation
• ROC domain dimerization
• Kinase activation loop flexibility

GTPase Cycle

The ROC domain functions as a GTPase:

GTP binding:

• Promotes LRRK2 dimerization
• Activates kinase domain
• Enables autophosphorylation

• ROC domain hydrolyzes GTP to GDP
• Regulated by COR domain
• Mutations affect hydrolysis rate

• Slow release rate
• Rate-limiting step
• Drug targeting opportunity

Expression Pattern

| Tissue | Expression Level |
|--------|-----------------|
| Brain (highest in substantia nigra) | High |
| Kidney | High |
| Lung | Moderate |
| Heart | Low-Moderate |
| Liver | Low |

Interacting Proteins

LRRK2 interacts with numerous proteins:

• α-Synuclein — Pathological interaction
• Parkin — Mitophagy regulation
• PINK1 — Mitochondrial quality control
• 14-3-3 proteins — Cytosolic anchoring
• VPS35 — Retromer component
• Rab proteins — Primary substrates
• MAPK components — Signaling pathways
• mTOR — Autophagy regulation

LRRK2-Rab Interaction Network

flowchart LR
classDef blue fill:#0a1929,stroke:#01579b,stroke-width:2px
classDef orange fill:#3e2200,stroke:#e65100,stroke-width:2px
classDef green fill:#0e2e10,stroke:#1b5e20,stroke-width:2px
classDef red fill:#3b1114,stroke:#b71c1c,stroke-width:2px

A["LRRK2"]:::blue -->|"phosphorylates"| B["Rab10"]:::orange
A -->|"phosphorylates"| C["Rab8A"]:::orange
A -->|"phosphorylates"| D["Rab12"]:::orange
A -->|"phosphorylates"| E["Rab35"]:::orange

B -->|"regulates"| F["Membrane Traffic"]:::green
C -->|"regulates"| G["Exocytosis"]:::green
D -->|"regulates"| H["Autophagy"]:::green
E -->|"regulates"| I["Endocytosis"]:::green

F -.->|"defect"| J["PD Pathogenesis"]:::red
G -.-> J
H -.-> J
I -.-> J

click A "/genes/lrrk2" "LRRK2 Gene"
click A "/proteins/lrrk2-protein" "LRRK2 Protein"
click H "/mechanisms/autophagy-lysosomal-pathway-parkinsons" "Autophagy Pathway"
click J "/diseases/parkinsons-disease" "Parkinson's Disease"

Neuroinflammation in LRRK2-PD

Microglial Activation

LRRK2 is highly expressed in microglia:

Activation markers:

• Iba1 upregulation
• CD68 expression

• IL-1β, IL-6, TNF-α

Research Directions

• Developing brain-penetrant kinase inhibitors
• Understanding kinase substrate specificity
• LRRK2 biomarkers development
• Gene therapy approaches

LRRK2 in Neurobiology

Neuronal Functions

LRRK2 plays important roles in neurons[@greggio2021]:

Synaptic function:

• Presynaptic vesicle cycling
• Dendritic spine morphology
• neurotransmitter release

• Axon guidance during development
• Mitochondrial transport
• Cytoskeletal dynamics

• MAPK pathway modulation
• Autophagy regulation
• Stress response

Glial Functions

LRRK2 is highly expressed in glia:

Microglia:

• Inflammatory responses
• Cytokine production
• Phagocytic activity

• Metabolic support
• Potassium buffering
• Neurotrophic support

Genetic Modifiers

Modifying Genes

The International LRRK2 Consortium has identified genetic modifiers[@gclass2020]:

Risk modifiers:

• GBA variants increase penetrance
• SNCA rs356219 increases risk
• BST1 variants modify risk

• Certain VPS35 variants
• Mitochondrial function genes

Penetrance

LRRK2 penetrance is modified by:

Brain Atlas Resources

• [Allen Human Brain Atlas - LRRK2 Expression](https://human.brain-map.org/microarray/search/show?search_term=LRRK2)
• [Allen Cell Type Atlas - LRRK2](https://celltypes.brain-map.org/)
• [BrainSpan - LRRK2 Developmental Expression](https://brainspan.org/)
• [Allen Mouse Brain Atlas - LRRK2](https://mouse.brain-map.org/)

Clinical Trials and Therapeutic Development

LRRK2-targeted therapies are in various stages of development [@muller2023]:

• LRRK2 kinase inhibitors: Several compounds in clinical trials including DNL151 (Denali) and BIIB122 (Biogen) [@sveinbjornsson2022]
• Antisense oligonucleotides: ASO therapies targeting LRRK2 mRNA [@zhao2021]
• Gene therapy approaches: AAV-mediated delivery of mutant LRRK2 siRNA [@brodacki2020]

Biomarkers

LRRK2 mutation carriers show specific biomarkers [@fang2022]:

• CSF biomarkers: Elevated tau protein levels
• Neuroimaging: Reduced dopamine transporter binding
• Clinical progression: Typically slower progression than sporadic PD

Animal Models

Key LRRK2 models include [@greggio2021]:

• Transgenic mice: G2019S mutant mice show dopaminergic neuron loss
• Knock-in models: BAC-LRRK2 G2019S mice
• Non-human primates: Primate models for translational studies

Pathogenic Variants

The G2019S mutation is the most common pathogenic variant [@kluss2022]:

• Prevalence: ~5% of familial PD, ~1% of sporadic PD
• Penetrance: Age-dependent, ~70% by age 80
• Phenotype: Similar to idiopathic PD but often earlier onset

Future Directions

Research priorities for LRRK2 [@alessi2023]:

• Kinase domain structure: Cryo-EM studies of full-length LRRK2
• Biological substrates: Identifying all LRRK2 phosphorylation targets
• Brain penetration: Developing CNS-penetrant inhibitors

References

LRRK2 Substrates

Understanding LRRK2 phosphorylation targets is crucial for drug development:

Direct Substrates

• Key regulators of membrane trafficking
• Phosphorylation at conserved Thr/Ser residues
• Impaired by pathogenic LRRK2 mutations

• ERK, JNK pathway interactions
• Neuronal survival signaling

• mTORC1 pathway modulation
• Lysosomal function regulation

Pathological Substrate Phosphorylation

• Hyperphosphorylation of Rab proteins in PD
• Disrupted vesicle trafficking
• Impaired synaptic function

Biomarkers

LRRK2 biomarker development focuses on:

Fluid Biomarkers

• CSF LRRK2 protein levels
• Phospho-Rab10 in blood/CSF
• Genetic modifiers in CSF

Imaging Biomarkers

• PET ligands for LRRK2 (in development)
• Neuroinflammation markers

See Also

• [Parkinson's Disease](/diseases/parkinsons-disease)
• [LRRK2 Gene](/genes/lrrk2)
• [Alpha-Synuclein](/proteins/alpha-synuclein)
• [Parkin](/genes/parkin)
• [PINK1](/genes/pink1)
• LRRK2 Pathway in Parkinson's Disease
• [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction)