BTK Protein

BTK Protein (Bruton's Tyrosine Kinase)

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4ea;">BTK</th></tr> [@dorward2021]
<tr><td><b>Gene</b></td><td>[BTK](/genes/btk)</td></tr>
<tr><td><b>UniProt ID</b></td><td>[Q06187](https://www.uniprot.org/uniprot/Q06187)</td></tr>
<tr><td><b>Molecular Weight</b></td><td>76 kDa</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Cytoplasm, plasma membrane</td></tr>
<tr><td><b>Protein Family</b></td><td>Tec family tyrosine kinase</td></tr>
<tr><td><b>Disease</b></td><td>X-linked agammaglobulinemia</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/mantle-cell-lymphoma" style="color:#ef9a9a">mantle cell lymphoma</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">4 edges</a></td>
</tr>
</table>
</div>

Overview

BTK (Bruton's Tyrosine Kinase) is a non-receptor tyrosine kinase belonging to the Tec family. The [BTK](/genes/btk) gene encodes a 659-amino acid protein originally characterized for its essential role in B cell receptor signaling and B cell development. Recently, BTK has emerged as a significant player in neuroinflammation and neurodegenerative diseases.

Structure

BTK contains multiple functional domains:

BTK Protein (Bruton's Tyrosine Kinase)

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4ea;">BTK</th></tr> [@dorward2021]
<tr><td><b>Gene</b></td><td>[BTK](/genes/btk)</td></tr>
<tr><td><b>UniProt ID</b></td><td>[Q06187](https://www.uniprot.org/uniprot/Q06187)</td></tr>
<tr><td><b>Molecular Weight</b></td><td>76 kDa</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Cytoplasm, plasma membrane</td></tr>
<tr><td><b>Protein Family</b></td><td>Tec family tyrosine kinase</td></tr>
<tr><td><b>Disease</b></td><td>X-linked agammaglobulinemia</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/mantle-cell-lymphoma" style="color:#ef9a9a">mantle cell lymphoma</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">4 edges</a></td>
</tr>
</table>
</div>

Overview

BTK (Bruton's Tyrosine Kinase) is a non-receptor tyrosine kinase belonging to the Tec family. The [BTK](/genes/btk) gene encodes a 659-amino acid protein originally characterized for its essential role in B cell receptor signaling and B cell development. Recently, BTK has emerged as a significant player in neuroinflammation and neurodegenerative diseases.

Structure

BTK contains multiple functional domains:

| Domain | Position | Function |
|--------|----------|----------|
| PH domain | N-terminal | Phosphoinositide binding, membrane localization |
| TH domain | Proline-rich | Proline-rich motifs for SH3 interactions |
| SH3 domain | Middle | Protein-protein interactions |
| SH2 domain | Middle | Phosphotyrosine binding |
| Kinase domain | C-terminal | Catalytic tyrosine kinase activity |

Biological Function

B Cell Receptor Signaling

BTK is essential for B cell development:

• Pre-BCR signaling in pro-B cells
• Mature BCR signaling
• B cell survival and proliferation
• Antibody production

Signaling Pathways

BTK activates multiple downstream pathways:

• PLCγ2: Calcium signaling, NFAT activation
• PI3K/AKT: Cell survival signaling
• [NF-κB](/entities/nf-kb): Transcriptional activation
• MAPK/ERK: Cell proliferation

Non-Immune Functions

BTK is expressed in:

• Macrophages: Inflammatory cytokine production
• [Microglia](/cell-types/microglia-neuroinflammation): Brain immune cells
• [Neurons](/entities/neurons): Developmental roles
• [Astrocytes](/entities/astrocytes): Glial function

Role in Neurodegeneration

Alzheimer's Disease

BTK in microglia contributes to AD pathogenesis:

Parkinson's Disease

• Microglial activation: BTK in dopaminergic degeneration
• Neuroinflammation: Chronic inflammation in PD brain
• Therapeutic target: BTK inhibitors in clinical trials for PD

Multiple Sclerosis

BTK inhibitors show promise:

• Reduces relapse rates
• Decreases new lesions
• Suppresses microglial activation

Therapeutic Implications

BTK Inhibitors

FDA-approved and experimental BTK inhibitors:

| Drug | Status | Indication |
|------|--------|------------|
| Ibrutinib | Approved | CLL, MCL, Waldenstrom |
| Acalabrutinib | Approved | CLL, MCL |
| Evobrutinib | Phase 3 | MS |
| Rilzabrutinib | Phase 3 | ITP, MS |

Neurodegeneration Trials

BTK inhibitors in development for:

• Alzheimer's disease (Phase 2)
• Parkinson's disease (Phase 1/2)
• Multiple sclerosis (Phase 3)

See Also

• [BTK Gene](/genes/btk)

External Links

• [GeneCards: BTK](https://www.genecards.org/cgi-bin/carddisp.pl?gene=BTK)

BTK in Neuroinflammation

Microglial BTK contributes to:

• Pro-inflammatory cytokine release: TNF-alpha, IL-1beta, IL-6
• Chemokine production: MCP-1, MIP-1alpha
• Cell surface marker expression: MHC class II, CD86
• antigen presentation: T cell activation

Clinical Trials

Current BTK inhibitor trials for neurodegeneration:

| Trial | Compound | Phase | Indication |
|-------|----------|-------|------------|
| HERO | Evobrutinib | Phase 3 | MS |
| Evolution | Tolebrutinib | Phase 3 | MS |
| NCT04848260 | Fenebrutinib | Phase 2 | MS |
| NCT04681833 | BIIB091 | Phase 1 | AD |

Safety Considerations

BTK inhibitor side effects:

• Bleeding risk: On-target platelet dysfunction
• Infections: Immunosuppression
• Atrial fibrillation: Cardiovascular effects
• Cytopenias: Blood count abnormalities

References